AMERICAN
JOURNAL
OF
Vol. 228, No. 1, January
PKYSIOLOCY
1975.
Printed
in
U.S.A.
Vasopressin
release
hemorrhage
and angiotensin
ROBERT
E. SHADE
AND
during
LEONARD
nonhypotensive I I infusion SHARE
D$+wtmantof Physiology and Biuj~hysics, Uniuersity of Tennessee Medical
SHARE. Vasopressin release SHADE, ROBERT E., AND LEONARD during nonhypotensiue hemorrhage and angiotensin II infusion. Am. J. 19 75 .-These experiments were dePhysiol. 228( 1) : 149-154. signed to determine whether angiotensin II (AH) could potentiate the increase in plasma vasopressin (ADH) concentration produced by continuous, nonhypotensive hemorrhage in nephrectomized dogs. infusion of AI1 (10 rig/kg 9min) into a common carotid artery in nonbled dogs did not increase plasma ADH levels, suggesting that increases in carotid arterial plasma AI1 concentration alone do not stimulate an increase in ADH release. Subsequently, nephrectomized dogs subjected to nonhypotensive hemorrhage (0.44 ml/kg amin) were infused as follows: 0.9 0/O saline intravenously, AlI1 (10 rig/kg min) intravenously, or AI1 ( 10 rig/kg qmin) into the carotid. The plasma ADEI concentration increased in all three groups of dogs during hemorrhage, Although the AIIinfused dogs demonstrated significant increases in plasma ADH levels earlier during hemorrhage, these changes were small; there were no statistically significant differences in plasma ADH concentrations among the three groups. These results suggest that increases in plasma AI1 concentration have little or no significant effect on the volume control of ADH release. l
antidiuretic
hormone;
ADH
SEVERAL RECENT INVESTIGATIONS have indicated that angiotensin II may be involved in the control of vasopressin (ADH) release. Bonjour and Malvin (3) have data that suggest that infusions of angiotensin in the conscious dog increase the plasma ADH concentration. Infusion of angiotensin II into a common cartoid artery was reported to be more effective in increasing the plasma ADH concentration than intravenous infusion, suggesting that angiotensin stimulated ADH release by an effect on the central nervous system (8). Ventriculocisternal infusions of small amounts of angiotensin 11 also stimulated ADH release (8), providing further support for this concept. On the other hand, previous investigations performed in this laboratory have been unable to confirm that increases in plasma angiotensin II alone can promote ADH release. Increases in plasma ADH concentration during hemorrhage were not altered significantly when renin release was prevented by clamping of the renal arteries and veins (4), and there were no significant changes in the plasma ADH concentration with either intravenous or intracarotid infusion of angiotensin II in the anesthetized dog (6). Whether or not ADH release can be stimulated by angiotensin II alone, there is good evidence that this agent can potentiate the release of ADH in response to an osmotic
Units, Memphis,
Tennessee 38163
stimulus ( IO). Therefore, the present study was designed to determine if exogenous angiotensin II could potentiate the release of ADH seen with a nonhypotensive, continuous hemorrhage. Bilateral nephrectomy 2 h before the experiment was used to produce low control values of plasma renin activity and to prevent changes in endogenous angiotensin II during the experiment. MATERIALS
AND
METHODS
These experiments were performed on 43 male mongrel dogs weighing 15-28 kg. Following sedation with morphine (0.1 ml/kg of 2 7o morphine sulfate in 0.9 % NaCl), anesthesia was induced with a mixture of 0.6 % chloralose and 6 % urethan in 0.9 % saline in a dose of approximately 9 ml/kg. Anesthesia was maintained with the chloralose and urethan solution, when required, by an intravenous injection of 30 ml. Surgery. All dogs were subjected to the following surgical preparation, Bilateral nephrectomy was performed by the retroperitoneal approach. Both femoral arteries and veins were cannulated, and a patent airway was maintained by insertion of a cuffed endotracheal tube. The tip of one of the femoral vein catheters was placed in the vena cava near its junction with the right atrium for monitoring of central venous pressure. In a11 of the dogs of protocol I (n = 13) and in 10 of the dogs in protocol II, a common carotid artery was exposed, and a Teflon catheter (B-D, Longdwel catheter, 22-gauge) was inserted into the vessel through a hypodermic needle in the direction of blood flow, with the tip of the catheter lying approximately l-2 cm below the thyrocarotid junction. The carotid artery was not ligated, and carotid blood Aow was, presumably, interfered with minimally. Following surgical preparation, there was a period of at least 2 h before either of the experimental protocols was started. Experimental procedure. Protocol I was followed in two groups of dogs. The control dogs (n = 7) received an intracarotid infusion of 0.9 % NaCl at 0.19 ml/min. The experimental group of dogs (n = 6) received an intracarotid infusion of angiotensin II (Hypertensin, Ciba), 10 rig/kg* min in 0.9 % NaCl at 0.19 ml/min. In both groups of dogs, control blood samples were collected before the start of the infusions, and experimental samples were taken 20, 25, 35, and 45 min after their start. Protocol II was followed in three groups of 10 dogs each (Fig. 1). After collection of control blood samples, one of the following infusions was made : 0.9 % saline (0.2 ml/min)
Downloaded from www.physiology.org/journal/ajplegacy at Midwestern Univ Lib (132.174.254.157) on February 14, 2019.
150
R.
E. SHADE
AND
L.
SHARE
RESULTS
Bllatercl Nephrdomy
I WAIT
TWO
I5 Mm
HOURS
L
5 IO 20 Min of Hemorrhage
30
I
I iTART HEMORRHAGE (0.44 ml/min START INFUSION I. 0 9% NaCI at 0.2 ml /min - CONTROL 2. IO ng AII /min INTRAVENOUS 3 IO ng AII /min INTRACAROTID FIG.
1. Experimental
procedure
in protocol
4 kg )
I.
intravenously; angiotensin II in 0.9 % saline (10 ng/kgm min, 0.2 ml/min) intravenously; angiotensin II in 0.9 % saline ( 10 rig/kg nrein, 0.2 ml/min) via the catheter in the common carotid artery. Fifteen minutes after the start of infusion, a continuous arterial hemorrhage of 0.44 ml/min kg was begun with the use of a Sage tubing pump. Subsequent experimental blood samples were collected after 5, 10, 20, and 30 min of continuous hemorrhage. In both protocols I and II, blood sampling involved drawing 30 ml of blood into an iced syringe wetted with sodium heparin (1,000 U/ml) for determination of plasma ADH, osmolality, sodium, and potassium. An additional 5 ml were collected in an iced syringe containing 0.1 ml 5 % EDTA in 0.9 % saline for determination of plasma renin activity. Each blood sample was replaced during sampling by an equal volume of 6 % dextran in 0.9 % saline. The blood samples were immediately placed in centrifuge tubes kept in ice. Measurements. Mean arterial blood pressure and arterial pulse pressure were determined with a Statham (P23 dB) strain-gauge transducer; central venous pressure was measured with a Statham P23 AA strain-gauge transducer. The zero pressure reference point was set at the level of the heart and was determined from past experience in open chest placement of left atria1 catheters. Mean heart rate was determined by a cardiotachometer. All analog data were recorded on a Brush Mark 260 recorder. Plasma osmolality was measured by freezing-point depression (Osme tte S. osmometer), and p lasma sodium and potassium concentrations were determined by a flame photometer with a lithium internal standard (Instrumentation Laboratory model 343). Hematocrit was measured in microhematocrit tubes. ADH was extracted from plasma and bioassayed as described previously (4, 9). Plasma renin activity (PRA) was determined by radioimmunoassay with a commercially available kit (Schwarz/Mann radioimmunoassay kit and E. R. Squibb 8r. Sons angiotensin I immunotope kit). Statisticalprocedures. Statistical significance between groups of dogs was determined by two-way analysis of variance for repeated measures in the same subject (1 I)+ Statistical significance of changes within a group was determined by one-way analysis of variance for repeated measures in the same subject (1 I). In the event of a significant effect, differences between means were determined by the NewmanKeuls procedure (11). Thus, the standard errors of the mean shown in the tables and figures were not used in the statistical analyses. Skewed distributions of the ADH values were indicated by Cochran’s test for homogeneity of variante. Therefore, all the ADH data were normalized for statistical analysis by transformation to natural logarithms. l
Pratocol 1. The results from protocol I are summarized in Tables 1, 2, and 3. Preinfusion PRA for both groups of dogs was 0.8 ng AI/ml 9h or less (Table 1). Plasma sodium and potassium concentrations and heart rate were identical or very similar in both groups of dogs (Table 2). Infusion of either saline or angiotensin II had no significant effect on heart rate and plasma sodium and potassium concentrations. Decreases in hematocrit occurred probably as a result of replacement of the blood samples with equal volumes of 6 % dextran solution. Mean arterial blood pressure held relatively constant in the saline-infused dogs (Table 3). AS expected, mean arterial blood pressure increased 20-30 mmHg (P < 0.01) in response to the intracarotid infusion of angiotensin II and remained elevated during the rest of the experiment (Table 3). There were no initial differences in central venous pressure and plasma osmolality between the two groups of dogs, and these variables did not change during the infusions. There were also no significant differTABLE
e+iments
1. Initial phma of jwotacol I Saline
renzh activity in ind~vdud _--
.----
Infusion
Angiotensin
0.3 0.3 0.4 0.3 0.3 0.4 0.3 liter
Initial plasma times hour,
0.2 0.5 0*2 0.7 0.6 0.8 renin
TABLE 2. Efect protocuz I
activity,
nanograms
of intracarotid
angiotensin
Controls meq/liter
HR,
beats/min
I-m
% Tnfrnr -w.-arotid
144
* HR,
beats/min
Hct,
%
145 zt
3.9 0.2 95
*9 41
I Values are pK = plasma hematocrit.
It2
I
2 3.9 * 0.2 105 zk 11 40 zt 3*
143 4 3.5 zt 0.4 109 * 7 35 & 4*
144 *4 3.9 It 0.3 113
144 -41
144 ztl
144 +I
3.8 0.1 115 =t: 11 38 It 2*
3.9 0.1 111 It 10 35 & 2*
4.0 0.2 117 *7 34 * 2*
It2
3.9 =ts: 0.3 96 * 5 39 s+ 3*
angiotensin
PK, meq/liter
145
*3
145 +2
PNa, meq/liter
of Infusion
(n = 7)
143 *2 3.9 =t: 0.2 90 zt5 42 +3
PK, meq/liter
I per milli-
infusion of angiotensin II,
Minutes
F&,
II Infusion
It zt + II
zk
3.8 0.3 92 15 38 4*
(n =
343 34 zt 4*
6)
It
*
It
1 .--
sodium concentration. means + SE. P Na = plasma potassium concentration. HR = heart rate. Hct * Significantly different from time 0 (P < .Ol).
Downloaded from www.physiology.org/journal/ajplegacy at Midwestern Univ Lib (132.174.254.157) on February 14, 2019.
=
ADH
DURING
TABLE
HEMORRHAGE
AND
Effect of ktracarotd
3.
AI1
151
INFUSION
infusion of angiotensh
11,
TABLE 4. Initial of protocol II
protocol I Minutes 0
1
Controls PAD&
d-J/ml
A
MABP,
mmHg
21.2 5.9 88
=t2 PP, mmHg
79 +8
CVP,
mmHg
2*9 + 0.8 322
P osm>
mosmol/kg (n = 3)
13.9 MABP,
mmHg
3.8 84
*4
PP, mmHg
95 *4
CVP,
mmHg It
P osm:
mosmol/kg
(n =
3.6 0.9 318
1
(n =
7)
14.8 rt 3.8 91 &4 87 *9 3*3 + 0.8 323
Angiotensin
+
20
II( 18.0 4.2 106 zt 4* 81 zt5 3.3 A 0.8 319 4l
of Infusion 25
zt
13.2 4.5 93
*3 83 *9 3.5 + 0.5 322
n
Control
1
35
14.2 * 4.4 97 +3 85 4x10 3.5 + 0.5 326
1
45
14.9 It 5.9 95 zt3 88 A9 3.6 + 0.6 325
: 6) 17.7 4.3 115 zt 3* 82 l 5 3.5 zt 0.8 316 *
16.6 3.6 116 zt 4* 82 *4 3.8 * 0.7
zt 0.7
324
321
+
13.4 2.2 118 AI 4* 84 *5 3.5 +
2)
Values concentration. rial pulse osmolality
~ AZ SE. P AI)H = plasma antidiuretic hormone MABP = mean arterial blood pressure. PP = artevenous pressure. PO,, = plasma pressure. CVP = central . * Significantly different from time 0 (P < .05), are
plasma renin activity in individual
means
ences between the groups in preinfusion plasma ADH concentrations. Plasma ADH levels during the intracarotid infusion of saline did not change significantly from preinfusion values. Similarly, intracarotid infusion of angiotensin II at 10 rig/kg min had no significant effect on plasma ADH when compared either with the preinfusi on observations or with the saline-infused dogs. Protocol 11. PRA during preinfusion conditions (control) was low for all of the dogs in each of the three groups of experiments. The highest preinfusion PRA was 1.1 rig/ml h, and the remaining values were 0.8 ng/mlv h or less (Table 4). plasma Plasma sodium and potassium concentrations, osmolality, and heart rate were similar in all three groups and did not change during hemorrhage (Table 5). Hematocrit was also initially the same in the three groups of dogs and decreased to the same extent during the experiments (since blood samples were replaced with equal volumes of 6 70 dextran solution) in the three groups of dogs (Table 5). The cardiovascular effects of infusion of angiotensin II at 10 rig/kg min were similar to those seen in protocol I. These results are summarized in Figs. 2-4. Intravenous and intracarotid infusion of angiotensin II increased mean arterial blood pressure (P < .Ol for both groups) approximately 20 mmHg (Fig. 2). Thus, mean arterial blood pressure was significantly higher in both angiotensin-infused groups of dogs than in dogs infused with 0.9 % saline alone (2’ < .Ol). However, there were no apparent or significant changes in l
l
Intravenous
Intracarotid
0.1 0.3 0.7
0.6 0.3 O*l
0.3 0.4 0.1
0.2 0.2
0.1 0.1
0.0
0.4 0.4
0.2 0.2 0.4 0.5 1.1
0.2 0.2 0.8 Initial milliliter
AI1
experiments
plasma times
renin
activity,
AEI
0.4 0.2 0.1 0.6 0.3
0.7 n anograms
angiotensin
I
per
hour.
mean arterial blood pressure for all three groups during a continuous hemorrhage of 0.44 ml/kg* min. There were no statistically significant differences in arterial pulse pressure between the control group and the two experimental groups before infusion or during continuous hemorrhage. There were also no significant changes in arterial pulse pressure within each group during hemorrhage, except for a transient increase of 13 mmHg in the saline-infused dogs seen afler 5 min of hemorrhage. Central venous pressure averaged 2-3 mmHg before the beginning of the infusions (Fig, 3) and tended to decrease during hemorrhage in all three groups. Although this effect appeared to be more pronounced in dogs with an intracarotid angiotensin II infusion, there were no significant differences in central venous pressure among the groups of dogs during the time course of the experiment. Preinfusion plasma ADH concentrations averaged between 14 and 21 r,lU/ml, and there were no statistically significant differences among the three groups of dogs (Fig. 4). In the saline-infused dogs, a statistically significant increase in ADH levels could only be detected after 30 min of hemorrhage. The plasma ADH concentration increased in the dogs receiving intravenous angiotensin after 5 min of hemorrhage. Further increases were seen after 20 and 30 min of hemorrhage. In the dogs which were infused with angiotensin via a common cartoid artery, the changes were statistically significant after 10, 20, and 30 min of hemorrhage. Finally, a two-way analysis of variance for repeated measures in the same subject could not detect any significant differences among any of the groups for the four experimental observations. Therefore, although the two angiotensin-infused groups demonstrated significant increases in plasma ADH earlier in the course of hemorrhage when compared to their own control values, these increases were small, and the saline-infused dogs had plasma ADH concentrations that were not detecta bly different from the angiotensin IIinfused dogs.
l
DISCUSSION
Investigations performed in several laboratories have suggested that ADH release may be directly stimulated by angiotensin ( l-3, 8). Some of these studies have used an indirect determination of ADH release by measuring changes in free water clearance in the experimen tal animal.
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152
R. E. SHADE
TABLE 5. E$eCt of intracarofid infusion of angzdensk during slow hemorrhage (protocol II>
Minutes
Controls
PNa,meq/liter PK,meq/liter mosmol/kg posm,
It It zt
HR,
beats/min *
Hct,
% zt Intravenous
PNa,
144 4 3.8 0.4 324 4 89 19 44 6
* PK,
meq/liter
P osm) mosmol/kg HR,
beats/min
Hct,
%
Intracarotid
PNa, meq/liter zt
PK, meq/liter It P
OSlIk>
mosmol/kg *
HR,
beats/min
Hct,
%
& It
* I+ +
144 3.9 0.6
It It
* rt zt +
145 4 4.0 * 0.7 325 It 4 105 zt 34 40 Et 2*
147 5 4.2 0.5 323 3 90 22 43 1
=t
3.9 0.5
xt 3216 105 It 29 41 ck 2* II
(n =
rt * Ik h zt
145 5 3.8 0.4 328 4 90 22 39 7*
PULSE
SHARE
PRESSURE
150 8 4.2 0.5 327 4 94 16 41 1”
145 5 3.8 * 0.4 329 * 3 92 r+ 21 38 s+ 7”
ARTERIAL
BLOOD
PRESSURE
*
”
It + It * It
5 10 Minutes of Hemorrhage
0
20
30
FIG. 2. Effect of angiotensin II (AII) infusion on arterial pulse pressure and mean arterial blood pressure during continuous hemorrhage. Open bars represent saline infusion, cross-hatched bars represent intravenous AII infusion, and closed bars represent carotid arterial AII infusion. Values represented are means + SE. * Significantly different from time 0 (P < .05). ** Significantly different from time 0
IO>
144
+
99 30 43 2*
+
h
zt
It4
It
*
(n =
!
~,“9
&
145 4 3.7 0.4 326 3 87 17 41 6”
It
*4
MEAN
I
A
II
angiotensin
146 4 4.2 0.4 327 5 83 16 43 1
IO>
144 4 3.7 Et 0.4 326 It 3 87 + 18 42 * 5*
+
*
L.
of Hemorrhage
&
angiotensin
144 4 4.0 rtz 0.4 325 * 4 90 zt 20 44 zt 2
lneq/liter
(n =
11
AND
145 5 4.0 0.6 326 3 110 40* 38 2*
10)
zt & * + +
147 3 4.2 0.5 324 4 94 20 39 1*
+ xt + zt It
5
148 5 4.1 0.5 326 4 93 14 38 1”
Values are means + SE. PN~ = plasma sodium concentration. PK = plasma potassium concentration, PO,, = plasma osmolality. I-IR = heart rate. Hct = hematocrit. * Significant from time (P < .Ol).
30
Minutes FIG.
during
3. Effect of angiotensin continuous hemorrhage.
of
Hemorrhage
II infusion on central venous pressure Key is identical to key of Fig. 2
bU
0
These results are open to question, since angiotensin may exert a direct antidiuretic effect on the kidney (I, 7, lo), and since in some situations a change in free water clearance is an unreliable index of a change in the plasma ADH concentration (12). Bonjour and Malvin (3) measured plasma ADH in conscious clogs receiving an intravenous infusion of angiotensin II. Angiotensin infused intravenously at a dose of 10 rig/kg min produced an increase in mean arterial blood pressure of 15 mmHg, and there was a small increase in plasma ADH of 0.9 PI-J/ml. One could argue that the angiotensin-induced increase in blood pressure in conscious dogs stimulated ADH release by an indirect action as a nonspecific stress. This view is supported by the observation that an infusion of 5 rig/kg nmin in the same group of conscious dogs did not produce an elevation in arterial blood pressure, and plasma ADH did not increase. Subsequent experiments from the same laboratory have shown that intravenous angiotensin at 10 &kg’ min in three pento-
0
5
0
Minutes FIG.
tration
10
20
30
of Hemorrhage
4. Effect of angiotensin II infusion on plasma during continuous hemorrhage. Key is identical
ADH concento Fig. 2.
l
barbital-anesthetized dogs had no effect on plasma ADH (8). Intracarotid infusion of angiotensin at the same dose and in the same three dogs produced increases in plasma ADH of 0.6-1.9 PI-J/ml. Efforts to reproduce these results in our laboratory have been unsuccessful in detecting any apparent or statistical increase in plasma ADH in seven anesthetized dogs receiving intracarotid infusions of angioI also tensin at 10 rig/kg min (6). The results of protocol fail to support the observations of these previous investigators (8). This series of experiments differs from previous l
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ADH
DURING
HEMORRHAGE
AND
AII
153
INFUSION
experiments in that endogenous levels of angiotensin II were presumably low due to bilateral nephrectomy. Nevertheless, intracarotid infusion of angiotensin II did not significantly increase plasma ADH concentration over preinfusion values. Furthermore, plasma ADH concentrations in the angiotensin-infused dogs were statistically identical with plasma ADH concentrations in bilaterally nephrectomized dogs receiving intracarotid saline infusions. Thus, increases in common carotid plasma angiotensin II levels were not associated with any signincant increase in ADH release. One possible explanation for the discrepancy between the results of protocol I and the experiments reported by Mouw and associates (8) is that the high control plasma levels of ADH in the present experiments could have prevented detection of small increases in plasma ADH during angiotensin II infusion, In the investigations reported by Mouw et al. (8), it appeared that experiments with higher control levels of plasma ADH concentration were associated with greater increases in plasma ADH concentration during ventriculocisternal infusion of angiotensin. These results suggest that the angiotensin infusion in protocol I should have produced large increases in plasma ADH concentrations. In addition, Shimizu, Share, and Claybaugh (IO) infused angiotensin II into a common carotid artery of anesthetized,‘ hydrated dogs and found no changes in plasma ADH associated with the angiotensin infusion when these dogs were compared to a control group of hydrated dogs receiving an intracarotid saline infusion. Since control values for the plasma ADH concentration were low in these dogs (mean less than 1.5 &J/ml), it appears unlikely that low preinfusion levels of plasma ADH are required for angiotensin II infusions to stimulate ADH release. It could also be argued that inhibition of ADH release due to increases in arterial blood pressure during angiotensin infusion could have obscured any possible direct stimulation of ADH release by angiotensin. The rate of infusion of angiotensin II (10 ng/kga min) in protocol I was the same as that reported by Bonjour and Malvin (3) and Mouw et al. (8), and their dogs experienced similar increases in blood pressure. In addition, Shimizu et al. (10) have demonstrated that increases in blood pressure of this magnitude, which accompanied angiotensin infusion, did not inhibit the increase in ADH release resulting from an osmotic stimulus. Therefore, it seems unlikely that our failure to observe a direct stimulation of ADH release by angiotensin in protocol I was due to interference by the increase in arterial blood pressure. Finally, plasma osmolality was constant throughout the experiment and therefore could not have had any influence on a possible direct stimulatory effect of angiotensin on ADH release. Although there is some question as to whether increases in plasma angiotensin alone will cause an increase in plasma ADH, there is conclusive evidence that angiotensin may potentiate the effect of a known stimulus for ADH release.
Shimizu and associates (10) found that when an intravenous infusion of 2.5 M NaCl was accompanied by infusion of angiotensin II at 10 ng/kgmmin into a common carotid artery, the increase in the plasma ADH concentration was much larger than with hypertonic saline alone. Andersson and Westbye (2) had similar findings when the angiotensin and hypertonic saline were injected into the cerebral ventricles. Thus, it can be concluded that angiotensin can potentiate the release of ADH due to an osmotic stimulus. The present experiments were designed to determine if increases in plasma levels of angiotensin II could also potentiate the release of ADH that occurs in response to a nonhypotensive decrease in blood volume (5). Previous experiments have shown that increases in plasma ADH as a result of hemorrhage could be dissociated from increases in endogenous plasma renin activity (4). However, since the control levels of plasma renin activity in these surgically prepared, anesthetized dogs were high, any effect of an increased plasma angiotensin concentration might have been at a maximum prior to hemorrhage. Therefore, the relationship between ADH release during hemorrhage and increased plasma angiotensin was studied in bilaterally nephrectomized dogs. This also provided the opportunity to determine the effects of hemorrhage on ADH under the conditions of low plasma renin activity. The results show that statistically significant increases in plasma ADH levels occurred with a nonhypotensive hemorrhage in saline-infused dogs and in dogs receiving either an intravenous or intracarotid infusion of angiotensin II at 10 rig/kg min (Fig. 4). Although the dogs receiving the angiotensin infusions demonstrated significant increases in plasma ADH concentration earlier in the course of hemorrhage, the absolute differences between the saline-infused dogs and the angiotensin-infused dogs were small and statistically insignificant. When these results are compared with the large potentiation of osmotically stimulated ADH release by angiotensin seen in a previous study (lo), it is concluded that increases in plasma angiotensin II do not appreciably alter the release of ADH due to a nonhypotensive hemorrhage. The resuhs of these experiments and previous experiments (10) would suggest that volume and osmotic control of ADH are to some degree independent and that angiotensin does not affect the final common pathway for ADH release. Thus, angiotensin may potentiate osmotically stimulated ADH release (lo), but has little or no effect on ADH release resulting from decreases in blood volume. l
The authors express their gratitude for the expert and enjoyable technical assistance provided by r\ls. J. T. Crofton, his. A. Place, and Mr. S. E. Pienaar. This work was supported by Public Health Service Grant HL-12990 from the National Heart and Lung Institute and Grant I-IL-14242 from the Specialized Center of Research in Hypertension. Computer assistance was provided by Public Health Service Grant HL-094Y5 from the National Heart and Lung Institute. Received
for
publication
1 March
1974.
REFERENCES 1. ANDERSSON, B., AND L. ERIKSSON. Conjoint action angiotensin on brain mechanisms controlling balances. Acta Physiol. &and. 81 : 18-29, 3971.
of sodium water and
and salt
2. ANDERSSON, B., AND 0. WESTBYE. and angiotensin on brain mechanisms Lip sci. 9 : 601-608, 1970.
Synergistic controlling
action
Downloaded from www.physiology.org/journal/ajplegacy at Midwestern Univ Lib (132.174.254.157) on February 14, 2019.
fluid
of sodium balance.
154
R.
3. BONJOUR, J. P., AND R. 1,. MAWIN. Stimulation of A,DH release by the renin-angiotensin system. Am. J. Physiol. 2 18 : 1555-1559, 1970. 4. CLAYBAUGW, J. R., AND LL. SHARE. Role of the renin-angiotensin system in the vasopressin response to hemorrhage. Endocrinology 90: 453-460, 19i’Z. 5. CLAYBAUGH, J. R., AND L. SHAKE. Vasopressin, renin and cardiovascular responses to continuous hemorrhage. Am. J. Physiol. 224: 519-523, 1973. 6. CLAYEAUGH, J- R., L. SHARE, AND K. SHIMXZU. The inability of infusions of angiotensin to elevate the plasma vasopressin concentration in the anesthetized dog. Endocrinology 90 : 1647-1652, 1972. 7. HEALY, J- K., C. BARCENA, J. h/l. B. O'CONNELL, AND G, E. SCI-IREINER. Renal and pressor action of angiotensin in the normal dog. Am. J. PhysioE. 208 : 1093-l 099, 1965.
E.
SHADE
AND
1;.
SHARE
8. Mouw,
D., J. P. BONJOUR, R. 1~. MALVIN, AND A, VANDER. Central action of angiotensin in stimulating ADH release. Am. J. Physiol. 220 : 239-242, 197 1. 9. SHARE, L. Acute reduction in extracellular fluid volume and the concentration of antidiuretic hormone in blood. Endocrinology 69 : 925-933, 1961. K., L, SHARE, AND J. R. CLAYBAUGH. Potentiation by 10. SIIIMIZU, angiotensin II of the vasopressin response to an increasing plasma osmolality. Endocrinology 93 : 42-50, 1973. R. R., AND F, J- ROHLF. Biometry. San Francisco: Free11. SOKAL, 12.
man &HA,
1969. J. E.,J.
A-JOHNSON,
sure, plasma osmolality, and Am. J. Physiol. 217: 1672-1680,
AND
W.
ADH
W. levels
MOORE. in the
Left
atria1
anesthetized
1969.
Downloaded from www.physiology.org/journal/ajplegacy at Midwestern Univ Lib (132.174.254.157) on February 14, 2019.
presewe.
JOURNAL
OF
Vol. 228, No. 1, January
PKYSIOLOCY
1975.
Printed
in
U.S.A.
Vasopressin
release
hemorrhage
and angiotensin
ROBERT
E. SHADE
AND
during
LEONARD
nonhypotensive I I infusion SHARE
D$+wtmantof Physiology and Biuj~hysics, Uniuersity of Tennessee Medical
SHARE. Vasopressin release SHADE, ROBERT E., AND LEONARD during nonhypotensiue hemorrhage and angiotensin II infusion. Am. J. 19 75 .-These experiments were dePhysiol. 228( 1) : 149-154. signed to determine whether angiotensin II (AH) could potentiate the increase in plasma vasopressin (ADH) concentration produced by continuous, nonhypotensive hemorrhage in nephrectomized dogs. infusion of AI1 (10 rig/kg 9min) into a common carotid artery in nonbled dogs did not increase plasma ADH levels, suggesting that increases in carotid arterial plasma AI1 concentration alone do not stimulate an increase in ADH release. Subsequently, nephrectomized dogs subjected to nonhypotensive hemorrhage (0.44 ml/kg amin) were infused as follows: 0.9 0/O saline intravenously, AlI1 (10 rig/kg min) intravenously, or AI1 ( 10 rig/kg qmin) into the carotid. The plasma ADEI concentration increased in all three groups of dogs during hemorrhage, Although the AIIinfused dogs demonstrated significant increases in plasma ADH levels earlier during hemorrhage, these changes were small; there were no statistically significant differences in plasma ADH concentrations among the three groups. These results suggest that increases in plasma AI1 concentration have little or no significant effect on the volume control of ADH release. l
antidiuretic
hormone;
ADH
SEVERAL RECENT INVESTIGATIONS have indicated that angiotensin II may be involved in the control of vasopressin (ADH) release. Bonjour and Malvin (3) have data that suggest that infusions of angiotensin in the conscious dog increase the plasma ADH concentration. Infusion of angiotensin II into a common cartoid artery was reported to be more effective in increasing the plasma ADH concentration than intravenous infusion, suggesting that angiotensin stimulated ADH release by an effect on the central nervous system (8). Ventriculocisternal infusions of small amounts of angiotensin 11 also stimulated ADH release (8), providing further support for this concept. On the other hand, previous investigations performed in this laboratory have been unable to confirm that increases in plasma angiotensin II alone can promote ADH release. Increases in plasma ADH concentration during hemorrhage were not altered significantly when renin release was prevented by clamping of the renal arteries and veins (4), and there were no significant changes in the plasma ADH concentration with either intravenous or intracarotid infusion of angiotensin II in the anesthetized dog (6). Whether or not ADH release can be stimulated by angiotensin II alone, there is good evidence that this agent can potentiate the release of ADH in response to an osmotic
Units, Memphis,
Tennessee 38163
stimulus ( IO). Therefore, the present study was designed to determine if exogenous angiotensin II could potentiate the release of ADH seen with a nonhypotensive, continuous hemorrhage. Bilateral nephrectomy 2 h before the experiment was used to produce low control values of plasma renin activity and to prevent changes in endogenous angiotensin II during the experiment. MATERIALS
AND
METHODS
These experiments were performed on 43 male mongrel dogs weighing 15-28 kg. Following sedation with morphine (0.1 ml/kg of 2 7o morphine sulfate in 0.9 % NaCl), anesthesia was induced with a mixture of 0.6 % chloralose and 6 % urethan in 0.9 % saline in a dose of approximately 9 ml/kg. Anesthesia was maintained with the chloralose and urethan solution, when required, by an intravenous injection of 30 ml. Surgery. All dogs were subjected to the following surgical preparation, Bilateral nephrectomy was performed by the retroperitoneal approach. Both femoral arteries and veins were cannulated, and a patent airway was maintained by insertion of a cuffed endotracheal tube. The tip of one of the femoral vein catheters was placed in the vena cava near its junction with the right atrium for monitoring of central venous pressure. In a11 of the dogs of protocol I (n = 13) and in 10 of the dogs in protocol II, a common carotid artery was exposed, and a Teflon catheter (B-D, Longdwel catheter, 22-gauge) was inserted into the vessel through a hypodermic needle in the direction of blood flow, with the tip of the catheter lying approximately l-2 cm below the thyrocarotid junction. The carotid artery was not ligated, and carotid blood Aow was, presumably, interfered with minimally. Following surgical preparation, there was a period of at least 2 h before either of the experimental protocols was started. Experimental procedure. Protocol I was followed in two groups of dogs. The control dogs (n = 7) received an intracarotid infusion of 0.9 % NaCl at 0.19 ml/min. The experimental group of dogs (n = 6) received an intracarotid infusion of angiotensin II (Hypertensin, Ciba), 10 rig/kg* min in 0.9 % NaCl at 0.19 ml/min. In both groups of dogs, control blood samples were collected before the start of the infusions, and experimental samples were taken 20, 25, 35, and 45 min after their start. Protocol II was followed in three groups of 10 dogs each (Fig. 1). After collection of control blood samples, one of the following infusions was made : 0.9 % saline (0.2 ml/min)
Downloaded from www.physiology.org/journal/ajplegacy at Midwestern Univ Lib (132.174.254.157) on February 14, 2019.
150
R.
E. SHADE
AND
L.
SHARE
RESULTS
Bllatercl Nephrdomy
I WAIT
TWO
I5 Mm
HOURS
L
5 IO 20 Min of Hemorrhage
30
I
I iTART HEMORRHAGE (0.44 ml/min START INFUSION I. 0 9% NaCI at 0.2 ml /min - CONTROL 2. IO ng AII /min INTRAVENOUS 3 IO ng AII /min INTRACAROTID FIG.
1. Experimental
procedure
in protocol
4 kg )
I.
intravenously; angiotensin II in 0.9 % saline (10 ng/kgm min, 0.2 ml/min) intravenously; angiotensin II in 0.9 % saline ( 10 rig/kg nrein, 0.2 ml/min) via the catheter in the common carotid artery. Fifteen minutes after the start of infusion, a continuous arterial hemorrhage of 0.44 ml/min kg was begun with the use of a Sage tubing pump. Subsequent experimental blood samples were collected after 5, 10, 20, and 30 min of continuous hemorrhage. In both protocols I and II, blood sampling involved drawing 30 ml of blood into an iced syringe wetted with sodium heparin (1,000 U/ml) for determination of plasma ADH, osmolality, sodium, and potassium. An additional 5 ml were collected in an iced syringe containing 0.1 ml 5 % EDTA in 0.9 % saline for determination of plasma renin activity. Each blood sample was replaced during sampling by an equal volume of 6 % dextran in 0.9 % saline. The blood samples were immediately placed in centrifuge tubes kept in ice. Measurements. Mean arterial blood pressure and arterial pulse pressure were determined with a Statham (P23 dB) strain-gauge transducer; central venous pressure was measured with a Statham P23 AA strain-gauge transducer. The zero pressure reference point was set at the level of the heart and was determined from past experience in open chest placement of left atria1 catheters. Mean heart rate was determined by a cardiotachometer. All analog data were recorded on a Brush Mark 260 recorder. Plasma osmolality was measured by freezing-point depression (Osme tte S. osmometer), and p lasma sodium and potassium concentrations were determined by a flame photometer with a lithium internal standard (Instrumentation Laboratory model 343). Hematocrit was measured in microhematocrit tubes. ADH was extracted from plasma and bioassayed as described previously (4, 9). Plasma renin activity (PRA) was determined by radioimmunoassay with a commercially available kit (Schwarz/Mann radioimmunoassay kit and E. R. Squibb 8r. Sons angiotensin I immunotope kit). Statisticalprocedures. Statistical significance between groups of dogs was determined by two-way analysis of variance for repeated measures in the same subject (1 I)+ Statistical significance of changes within a group was determined by one-way analysis of variance for repeated measures in the same subject (1 I). In the event of a significant effect, differences between means were determined by the NewmanKeuls procedure (11). Thus, the standard errors of the mean shown in the tables and figures were not used in the statistical analyses. Skewed distributions of the ADH values were indicated by Cochran’s test for homogeneity of variante. Therefore, all the ADH data were normalized for statistical analysis by transformation to natural logarithms. l
Pratocol 1. The results from protocol I are summarized in Tables 1, 2, and 3. Preinfusion PRA for both groups of dogs was 0.8 ng AI/ml 9h or less (Table 1). Plasma sodium and potassium concentrations and heart rate were identical or very similar in both groups of dogs (Table 2). Infusion of either saline or angiotensin II had no significant effect on heart rate and plasma sodium and potassium concentrations. Decreases in hematocrit occurred probably as a result of replacement of the blood samples with equal volumes of 6 % dextran solution. Mean arterial blood pressure held relatively constant in the saline-infused dogs (Table 3). AS expected, mean arterial blood pressure increased 20-30 mmHg (P < 0.01) in response to the intracarotid infusion of angiotensin II and remained elevated during the rest of the experiment (Table 3). There were no initial differences in central venous pressure and plasma osmolality between the two groups of dogs, and these variables did not change during the infusions. There were also no significant differTABLE
e+iments
1. Initial phma of jwotacol I Saline
renzh activity in ind~vdud _--
.----
Infusion
Angiotensin
0.3 0.3 0.4 0.3 0.3 0.4 0.3 liter
Initial plasma times hour,
0.2 0.5 0*2 0.7 0.6 0.8 renin
TABLE 2. Efect protocuz I
activity,
nanograms
of intracarotid
angiotensin
Controls meq/liter
HR,
beats/min
I-m
% Tnfrnr -w.-arotid
144
* HR,
beats/min
Hct,
%
145 zt
3.9 0.2 95
*9 41
I Values are pK = plasma hematocrit.
It2
I
2 3.9 * 0.2 105 zk 11 40 zt 3*
143 4 3.5 zt 0.4 109 * 7 35 & 4*
144 *4 3.9 It 0.3 113
144 -41
144 ztl
144 +I
3.8 0.1 115 =t: 11 38 It 2*
3.9 0.1 111 It 10 35 & 2*
4.0 0.2 117 *7 34 * 2*
It2
3.9 =ts: 0.3 96 * 5 39 s+ 3*
angiotensin
PK, meq/liter
145
*3
145 +2
PNa, meq/liter
of Infusion
(n = 7)
143 *2 3.9 =t: 0.2 90 zt5 42 +3
PK, meq/liter
I per milli-
infusion of angiotensin II,
Minutes
F&,
II Infusion
It zt + II
zk
3.8 0.3 92 15 38 4*
(n =
343 34 zt 4*
6)
It
*
It
1 .--
sodium concentration. means + SE. P Na = plasma potassium concentration. HR = heart rate. Hct * Significantly different from time 0 (P < .Ol).
Downloaded from www.physiology.org/journal/ajplegacy at Midwestern Univ Lib (132.174.254.157) on February 14, 2019.
=
ADH
DURING
TABLE
HEMORRHAGE
AND
Effect of ktracarotd
3.
AI1
151
INFUSION
infusion of angiotensh
11,
TABLE 4. Initial of protocol II
protocol I Minutes 0
1
Controls PAD&
d-J/ml
A
MABP,
mmHg
21.2 5.9 88
=t2 PP, mmHg
79 +8
CVP,
mmHg
2*9 + 0.8 322
P osm>
mosmol/kg (n = 3)
13.9 MABP,
mmHg
3.8 84
*4
PP, mmHg
95 *4
CVP,
mmHg It
P osm:
mosmol/kg
(n =
3.6 0.9 318
1
(n =
7)
14.8 rt 3.8 91 &4 87 *9 3*3 + 0.8 323
Angiotensin
+
20
II( 18.0 4.2 106 zt 4* 81 zt5 3.3 A 0.8 319 4l
of Infusion 25
zt
13.2 4.5 93
*3 83 *9 3.5 + 0.5 322
n
Control
1
35
14.2 * 4.4 97 +3 85 4x10 3.5 + 0.5 326
1
45
14.9 It 5.9 95 zt3 88 A9 3.6 + 0.6 325
: 6) 17.7 4.3 115 zt 3* 82 l 5 3.5 zt 0.8 316 *
16.6 3.6 116 zt 4* 82 *4 3.8 * 0.7
zt 0.7
324
321
+
13.4 2.2 118 AI 4* 84 *5 3.5 +
2)
Values concentration. rial pulse osmolality
~ AZ SE. P AI)H = plasma antidiuretic hormone MABP = mean arterial blood pressure. PP = artevenous pressure. PO,, = plasma pressure. CVP = central . * Significantly different from time 0 (P < .05), are
plasma renin activity in individual
means
ences between the groups in preinfusion plasma ADH concentrations. Plasma ADH levels during the intracarotid infusion of saline did not change significantly from preinfusion values. Similarly, intracarotid infusion of angiotensin II at 10 rig/kg min had no significant effect on plasma ADH when compared either with the preinfusi on observations or with the saline-infused dogs. Protocol 11. PRA during preinfusion conditions (control) was low for all of the dogs in each of the three groups of experiments. The highest preinfusion PRA was 1.1 rig/ml h, and the remaining values were 0.8 ng/mlv h or less (Table 4). plasma Plasma sodium and potassium concentrations, osmolality, and heart rate were similar in all three groups and did not change during hemorrhage (Table 5). Hematocrit was also initially the same in the three groups of dogs and decreased to the same extent during the experiments (since blood samples were replaced with equal volumes of 6 70 dextran solution) in the three groups of dogs (Table 5). The cardiovascular effects of infusion of angiotensin II at 10 rig/kg min were similar to those seen in protocol I. These results are summarized in Figs. 2-4. Intravenous and intracarotid infusion of angiotensin II increased mean arterial blood pressure (P < .Ol for both groups) approximately 20 mmHg (Fig. 2). Thus, mean arterial blood pressure was significantly higher in both angiotensin-infused groups of dogs than in dogs infused with 0.9 % saline alone (2’ < .Ol). However, there were no apparent or significant changes in l
l
Intravenous
Intracarotid
0.1 0.3 0.7
0.6 0.3 O*l
0.3 0.4 0.1
0.2 0.2
0.1 0.1
0.0
0.4 0.4
0.2 0.2 0.4 0.5 1.1
0.2 0.2 0.8 Initial milliliter
AI1
experiments
plasma times
renin
activity,
AEI
0.4 0.2 0.1 0.6 0.3
0.7 n anograms
angiotensin
I
per
hour.
mean arterial blood pressure for all three groups during a continuous hemorrhage of 0.44 ml/kg* min. There were no statistically significant differences in arterial pulse pressure between the control group and the two experimental groups before infusion or during continuous hemorrhage. There were also no significant changes in arterial pulse pressure within each group during hemorrhage, except for a transient increase of 13 mmHg in the saline-infused dogs seen afler 5 min of hemorrhage. Central venous pressure averaged 2-3 mmHg before the beginning of the infusions (Fig, 3) and tended to decrease during hemorrhage in all three groups. Although this effect appeared to be more pronounced in dogs with an intracarotid angiotensin II infusion, there were no significant differences in central venous pressure among the groups of dogs during the time course of the experiment. Preinfusion plasma ADH concentrations averaged between 14 and 21 r,lU/ml, and there were no statistically significant differences among the three groups of dogs (Fig. 4). In the saline-infused dogs, a statistically significant increase in ADH levels could only be detected after 30 min of hemorrhage. The plasma ADH concentration increased in the dogs receiving intravenous angiotensin after 5 min of hemorrhage. Further increases were seen after 20 and 30 min of hemorrhage. In the dogs which were infused with angiotensin via a common cartoid artery, the changes were statistically significant after 10, 20, and 30 min of hemorrhage. Finally, a two-way analysis of variance for repeated measures in the same subject could not detect any significant differences among any of the groups for the four experimental observations. Therefore, although the two angiotensin-infused groups demonstrated significant increases in plasma ADH earlier in the course of hemorrhage when compared to their own control values, these increases were small, and the saline-infused dogs had plasma ADH concentrations that were not detecta bly different from the angiotensin IIinfused dogs.
l
DISCUSSION
Investigations performed in several laboratories have suggested that ADH release may be directly stimulated by angiotensin ( l-3, 8). Some of these studies have used an indirect determination of ADH release by measuring changes in free water clearance in the experimen tal animal.
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152
R. E. SHADE
TABLE 5. E$eCt of intracarofid infusion of angzdensk during slow hemorrhage (protocol II>
Minutes
Controls
PNa,meq/liter PK,meq/liter mosmol/kg posm,
It It zt
HR,
beats/min *
Hct,
% zt Intravenous
PNa,
144 4 3.8 0.4 324 4 89 19 44 6
* PK,
meq/liter
P osm) mosmol/kg HR,
beats/min
Hct,
%
Intracarotid
PNa, meq/liter zt
PK, meq/liter It P
OSlIk>
mosmol/kg *
HR,
beats/min
Hct,
%
& It
* I+ +
144 3.9 0.6
It It
* rt zt +
145 4 4.0 * 0.7 325 It 4 105 zt 34 40 Et 2*
147 5 4.2 0.5 323 3 90 22 43 1
=t
3.9 0.5
xt 3216 105 It 29 41 ck 2* II
(n =
rt * Ik h zt
145 5 3.8 0.4 328 4 90 22 39 7*
PULSE
SHARE
PRESSURE
150 8 4.2 0.5 327 4 94 16 41 1”
145 5 3.8 * 0.4 329 * 3 92 r+ 21 38 s+ 7”
ARTERIAL
BLOOD
PRESSURE
*
”
It + It * It
5 10 Minutes of Hemorrhage
0
20
30
FIG. 2. Effect of angiotensin II (AII) infusion on arterial pulse pressure and mean arterial blood pressure during continuous hemorrhage. Open bars represent saline infusion, cross-hatched bars represent intravenous AII infusion, and closed bars represent carotid arterial AII infusion. Values represented are means + SE. * Significantly different from time 0 (P < .05). ** Significantly different from time 0
IO>
144
+
99 30 43 2*
+
h
zt
It4
It
*
(n =
!
~,“9
&
145 4 3.7 0.4 326 3 87 17 41 6”
It
*4
MEAN
I
A
II
angiotensin
146 4 4.2 0.4 327 5 83 16 43 1
IO>
144 4 3.7 Et 0.4 326 It 3 87 + 18 42 * 5*
+
*
L.
of Hemorrhage
&
angiotensin
144 4 4.0 rtz 0.4 325 * 4 90 zt 20 44 zt 2
lneq/liter
(n =
11
AND
145 5 4.0 0.6 326 3 110 40* 38 2*
10)
zt & * + +
147 3 4.2 0.5 324 4 94 20 39 1*
+ xt + zt It
5
148 5 4.1 0.5 326 4 93 14 38 1”
Values are means + SE. PN~ = plasma sodium concentration. PK = plasma potassium concentration, PO,, = plasma osmolality. I-IR = heart rate. Hct = hematocrit. * Significant from time (P < .Ol).
30
Minutes FIG.
during
3. Effect of angiotensin continuous hemorrhage.
of
Hemorrhage
II infusion on central venous pressure Key is identical to key of Fig. 2
bU
0
These results are open to question, since angiotensin may exert a direct antidiuretic effect on the kidney (I, 7, lo), and since in some situations a change in free water clearance is an unreliable index of a change in the plasma ADH concentration (12). Bonjour and Malvin (3) measured plasma ADH in conscious clogs receiving an intravenous infusion of angiotensin II. Angiotensin infused intravenously at a dose of 10 rig/kg min produced an increase in mean arterial blood pressure of 15 mmHg, and there was a small increase in plasma ADH of 0.9 PI-J/ml. One could argue that the angiotensin-induced increase in blood pressure in conscious dogs stimulated ADH release by an indirect action as a nonspecific stress. This view is supported by the observation that an infusion of 5 rig/kg nmin in the same group of conscious dogs did not produce an elevation in arterial blood pressure, and plasma ADH did not increase. Subsequent experiments from the same laboratory have shown that intravenous angiotensin at 10 &kg’ min in three pento-
0
5
0
Minutes FIG.
tration
10
20
30
of Hemorrhage
4. Effect of angiotensin II infusion on plasma during continuous hemorrhage. Key is identical
ADH concento Fig. 2.
l
barbital-anesthetized dogs had no effect on plasma ADH (8). Intracarotid infusion of angiotensin at the same dose and in the same three dogs produced increases in plasma ADH of 0.6-1.9 PI-J/ml. Efforts to reproduce these results in our laboratory have been unsuccessful in detecting any apparent or statistical increase in plasma ADH in seven anesthetized dogs receiving intracarotid infusions of angioI also tensin at 10 rig/kg min (6). The results of protocol fail to support the observations of these previous investigators (8). This series of experiments differs from previous l
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ADH
DURING
HEMORRHAGE
AND
AII
153
INFUSION
experiments in that endogenous levels of angiotensin II were presumably low due to bilateral nephrectomy. Nevertheless, intracarotid infusion of angiotensin II did not significantly increase plasma ADH concentration over preinfusion values. Furthermore, plasma ADH concentrations in the angiotensin-infused dogs were statistically identical with plasma ADH concentrations in bilaterally nephrectomized dogs receiving intracarotid saline infusions. Thus, increases in common carotid plasma angiotensin II levels were not associated with any signincant increase in ADH release. One possible explanation for the discrepancy between the results of protocol I and the experiments reported by Mouw and associates (8) is that the high control plasma levels of ADH in the present experiments could have prevented detection of small increases in plasma ADH during angiotensin II infusion, In the investigations reported by Mouw et al. (8), it appeared that experiments with higher control levels of plasma ADH concentration were associated with greater increases in plasma ADH concentration during ventriculocisternal infusion of angiotensin. These results suggest that the angiotensin infusion in protocol I should have produced large increases in plasma ADH concentrations. In addition, Shimizu, Share, and Claybaugh (IO) infused angiotensin II into a common carotid artery of anesthetized,‘ hydrated dogs and found no changes in plasma ADH associated with the angiotensin infusion when these dogs were compared to a control group of hydrated dogs receiving an intracarotid saline infusion. Since control values for the plasma ADH concentration were low in these dogs (mean less than 1.5 &J/ml), it appears unlikely that low preinfusion levels of plasma ADH are required for angiotensin II infusions to stimulate ADH release. It could also be argued that inhibition of ADH release due to increases in arterial blood pressure during angiotensin infusion could have obscured any possible direct stimulation of ADH release by angiotensin. The rate of infusion of angiotensin II (10 ng/kga min) in protocol I was the same as that reported by Bonjour and Malvin (3) and Mouw et al. (8), and their dogs experienced similar increases in blood pressure. In addition, Shimizu et al. (10) have demonstrated that increases in blood pressure of this magnitude, which accompanied angiotensin infusion, did not inhibit the increase in ADH release resulting from an osmotic stimulus. Therefore, it seems unlikely that our failure to observe a direct stimulation of ADH release by angiotensin in protocol I was due to interference by the increase in arterial blood pressure. Finally, plasma osmolality was constant throughout the experiment and therefore could not have had any influence on a possible direct stimulatory effect of angiotensin on ADH release. Although there is some question as to whether increases in plasma angiotensin alone will cause an increase in plasma ADH, there is conclusive evidence that angiotensin may potentiate the effect of a known stimulus for ADH release.
Shimizu and associates (10) found that when an intravenous infusion of 2.5 M NaCl was accompanied by infusion of angiotensin II at 10 ng/kgmmin into a common carotid artery, the increase in the plasma ADH concentration was much larger than with hypertonic saline alone. Andersson and Westbye (2) had similar findings when the angiotensin and hypertonic saline were injected into the cerebral ventricles. Thus, it can be concluded that angiotensin can potentiate the release of ADH due to an osmotic stimulus. The present experiments were designed to determine if increases in plasma levels of angiotensin II could also potentiate the release of ADH that occurs in response to a nonhypotensive decrease in blood volume (5). Previous experiments have shown that increases in plasma ADH as a result of hemorrhage could be dissociated from increases in endogenous plasma renin activity (4). However, since the control levels of plasma renin activity in these surgically prepared, anesthetized dogs were high, any effect of an increased plasma angiotensin concentration might have been at a maximum prior to hemorrhage. Therefore, the relationship between ADH release during hemorrhage and increased plasma angiotensin was studied in bilaterally nephrectomized dogs. This also provided the opportunity to determine the effects of hemorrhage on ADH under the conditions of low plasma renin activity. The results show that statistically significant increases in plasma ADH levels occurred with a nonhypotensive hemorrhage in saline-infused dogs and in dogs receiving either an intravenous or intracarotid infusion of angiotensin II at 10 rig/kg min (Fig. 4). Although the dogs receiving the angiotensin infusions demonstrated significant increases in plasma ADH concentration earlier in the course of hemorrhage, the absolute differences between the saline-infused dogs and the angiotensin-infused dogs were small and statistically insignificant. When these results are compared with the large potentiation of osmotically stimulated ADH release by angiotensin seen in a previous study (lo), it is concluded that increases in plasma angiotensin II do not appreciably alter the release of ADH due to a nonhypotensive hemorrhage. The resuhs of these experiments and previous experiments (10) would suggest that volume and osmotic control of ADH are to some degree independent and that angiotensin does not affect the final common pathway for ADH release. Thus, angiotensin may potentiate osmotically stimulated ADH release (lo), but has little or no effect on ADH release resulting from decreases in blood volume. l
The authors express their gratitude for the expert and enjoyable technical assistance provided by r\ls. J. T. Crofton, his. A. Place, and Mr. S. E. Pienaar. This work was supported by Public Health Service Grant HL-12990 from the National Heart and Lung Institute and Grant I-IL-14242 from the Specialized Center of Research in Hypertension. Computer assistance was provided by Public Health Service Grant HL-094Y5 from the National Heart and Lung Institute. Received
for
publication
1 March
1974.
REFERENCES 1. ANDERSSON, B., AND L. ERIKSSON. Conjoint action angiotensin on brain mechanisms controlling balances. Acta Physiol. &and. 81 : 18-29, 3971.
of sodium water and
and salt
2. ANDERSSON, B., AND 0. WESTBYE. and angiotensin on brain mechanisms Lip sci. 9 : 601-608, 1970.
Synergistic controlling
action
Downloaded from www.physiology.org/journal/ajplegacy at Midwestern Univ Lib (132.174.254.157) on February 14, 2019.
fluid
of sodium balance.
154
R.
3. BONJOUR, J. P., AND R. 1,. MAWIN. Stimulation of A,DH release by the renin-angiotensin system. Am. J. Physiol. 2 18 : 1555-1559, 1970. 4. CLAYBAUGW, J. R., AND LL. SHARE. Role of the renin-angiotensin system in the vasopressin response to hemorrhage. Endocrinology 90: 453-460, 19i’Z. 5. CLAYBAUGH, J. R., AND L. SHAKE. Vasopressin, renin and cardiovascular responses to continuous hemorrhage. Am. J. Physiol. 224: 519-523, 1973. 6. CLAYEAUGH, J- R., L. SHARE, AND K. SHIMXZU. The inability of infusions of angiotensin to elevate the plasma vasopressin concentration in the anesthetized dog. Endocrinology 90 : 1647-1652, 1972. 7. HEALY, J- K., C. BARCENA, J. h/l. B. O'CONNELL, AND G, E. SCI-IREINER. Renal and pressor action of angiotensin in the normal dog. Am. J. PhysioE. 208 : 1093-l 099, 1965.
E.
SHADE
AND
1;.
SHARE
8. Mouw,
D., J. P. BONJOUR, R. 1~. MALVIN, AND A, VANDER. Central action of angiotensin in stimulating ADH release. Am. J. Physiol. 220 : 239-242, 197 1. 9. SHARE, L. Acute reduction in extracellular fluid volume and the concentration of antidiuretic hormone in blood. Endocrinology 69 : 925-933, 1961. K., L, SHARE, AND J. R. CLAYBAUGH. Potentiation by 10. SIIIMIZU, angiotensin II of the vasopressin response to an increasing plasma osmolality. Endocrinology 93 : 42-50, 1973. R. R., AND F, J- ROHLF. Biometry. San Francisco: Free11. SOKAL, 12.
man &HA,
1969. J. E.,J.
A-JOHNSON,
sure, plasma osmolality, and Am. J. Physiol. 217: 1672-1680,
AND
W.
ADH
W. levels
MOORE. in the
Left
atria1
anesthetized
1969.
Downloaded from www.physiology.org/journal/ajplegacy at Midwestern Univ Lib (132.174.254.157) on February 14, 2019.
presewe.
