BLOOD PRESSURE
1992; 1: 157-161
Plasma Atrial Natriuretic Peptide (ANP) Concentration in Patients with Pheochromocytoma K. STEPNIAKOWSKI, A. JANUSZEWICZ, M. LAPINSKI, T. FELTYNOWSKI, J. CHODAKOWSKA, H. IGNATOWSKA-SWITALSKA, B. WOCIAL and W. JANUSZEWICZ From the Department of Hypertension and Angiology. Institute of Internal Medicine, Warsaw. Poland
Blood Press Downloaded from informahealthcare.com by Ohio State University Libraries on 12/02/14 For personal use only.
StepniakowskiK, Januszewicz A, Lapikki M, Feltywwski T, ChodakowskaJ, Ignatowska-Switalska H, Wocial B, Januszewicz W. Plasmaatrialnarriureticpeptide( A N P ) concentration inpatients wjth~heoc~romocytoma. Blood Pressure 1992; 1: 157-161. The interaction between catecholamines (CA) and ANP is not clearly established. The effects of excess endogenous CA on ANP secretion can be investigated in patients with pheochromocytorna. We studied 27 patients with surgically and histologically proven pheochromocytoma (P) aged 19-70 years. In 16 of these patients plasma ANP study was repeated after surgical removal of the tumour. The control group (C) consisted of 20 healthy volunteers aged 21-48 years. Moreover, 42 patients with uncomplicated mild to moderate essential hypertension (EH) aged 18-48 years were also studied. In P higher plasmaANPconcentrationversusC, EH wasfound(51.9f8.1;25.5+ 1.5; 19.3+ 1.5fmol/ml,respectively).In 16patients with P, increased plasma ANP level (mean 63.3 & 12.6 fmol/ml) declined after surgical removal of the tumour (mean 22.4+ 2.9 fmol/ ml). In the P patients no relationship was found between plasma ANP and hormonal patterns of the tumour or between plasma ANP and plasma catecholamines, whereas significant positive correlations between plasma ANP and both systolic and diastolic blood pressure and heart rate were demonstrated. These results suggest that excess CA produced by the chromaffin tumour induce ANP secretion via stimulation of adrenergic receptors. However, influence of the haemodynamic changes evoked by CA cannot be excluded. It is suggested that increased secretion of ANP may be of some importance in maintaining blood pressure homeostasis in patients with pheochromocytorna. Key words; pheochromocytoma, atrial narriuretic peptide, noradrenaline, adrenaline.
INTRODUCTION Atrial natriuretic peptide (ANP) is a hormone with natriuretic, diuretic and vasodilatory properties, produced by the heart [l, 21. The most potent stimulus for ANP secretion is the stretch of the atrium [3,4]. Some experimental and clinical data indicate that the sympathetic nervous system may also influence the secretion of ANP [5-121. However, the interaction between catecholamines (CA) and ANP is not clearly established [13,14]. Pheochromocytoma is a good model for investigating the effects of the excess of endogenous CA on ANP secretion. The aim of this study was therefore to determine plasma ANP concentration in patients with pheochromocytorna and to investigate the interrelationship between catecholamines and ANP.
MATERIAL AND METHODS We studied 27 patients (17 women and 10 men) with surgically and histologically proven pheochromocytoma, aged 19 to 70 years. Twelve of these patients had paroxysmal hypertension, and in 15 patients the hypertension was sustained. None had symptoms of catecholamine cardiomyopathy or heart failure. The control group consisted of 20 healthy normotensive volunteers (12 women and 8 men), aged 21 to 48 years. Moreover, 42 patients with uncomplicated, mild to moderate essential hypertension (1 1 women, 31 men), aged I8 to 46 years were studied.
The subjects were hospitalized and maintained on a diet with normal content of sodium and potassium; any drugs were withdrawn for a t least 2 weeks before the study. All participants gave informed consent to the investigations. On the morning of the study, following an overnight fast, and after the 24-h urine collection was started, the patients remained recumbent and a Teflon cannula was inserted into an antecubital vein. At least 30 min afterwards the blood pressure was measured with a mercury sphygmomanometer, the 5th Korotkoff's phase being taken for the diastolic cut-off point. Blood samples were drawn from the cannula immediately thereafter and were placed in chilled polypropylene tubes containing aprotonin and Na verseniane for determination of atrial natriuretic peptide (ANP). All samples were immediately centrifuged at +4°C and aliquots of plasma were frozen at - 20" C until assayed. ANP plasma concentration was determined by radioimmunoassay using Peninsula antibodies and Amersham iodinated ANP. Extraction of ANP from plasma was performed by means of SEPPACK C- I8 cartridges (Waters Associated, Milford, MA USA). Recovery after extraction was 88.4%, detection limit was 1 pg per tube, and interassay coefficient of variation was 6%. Plasma concentration of catecholamines was determined by radioenzymatic procedure using a commercial kit. Urinary excretion of catecholamines was determined by fluorometric methods [15, 161. In 16 of the patients with pheochromocytorna
158
K . Stepniakowski et al.
Table I. Plasma A N P concentration and blood pressure in patients with pheochromocytoma, essential hypertension and in the control group Zk SE are shown. The letters indicate significant differences between groups by Student's unpaired t-test. p < 0.05. a-P vs C, &P vs EH, C-EH vs C .
Blood Press Downloaded from informahealthcare.com by Ohio State University Libraries on 12/02/14 For personal use only.
SBP (mmHg) DBP (mmHg) ANP (fmol/ml)
P (n=27)
EH (n=42)
C (n=20)
139+6" 90 f4" 51.9+8.1ab
153k3' 92 k 2" 25.5k 1.5
118f2 71 1 2 19.3+ 1.5
plasma ANP study was repeated 2 weeks after surgical removal of the tumor. Statistical analysis was performed using Student's ttest for paired and non-paired data. Correlation coefficients were calculated by the least-squares method. Levels of significance were set at a p-value less than 0.05. RESULTS Blood pressure and plasma ANP concentration of the investigated groups of patients are shown in Table I. The mean plasma ANP concentration in patients with pheochromocytoma (P) was significantly higher in comparison with patients with essential hypertension (EH) and normotensive controls (C) (5 1.9f8.1, 25.5 f 1S, 19.3f 1.5 fmol/ml respectively; P vs EH p < 0.05; P vs C p < 0.05). No differencesinplasma ANP concentrations between patients with essential hypertension and normotensive controls were found (Fig. 1). It should be pointed out that in 8 pheochromocytoma patients plasma ANP concentration remained within the range of normotensive control values.
ANP 'O0
l'O
i
PHEO 11-27
EH 1-1-42
C n-20
0
t
j t t
f
Fig. 1. Plasma ANP concentrationin patients with pheochromocytoma (PHEO), essential hypertension ( E H ) and in the control group ( C ) .
Hormonal pattern of the tumors was established on the basis of urinary excretion of free noradrenaline and adrenaline. Thirteen patients excreted excessive amounts of both catecholamines; in another 13 cases we found only an increased excretion of NA, while in one patient urinary excretion of both NA and A was normal. Plasma ANP level in relation to the hormonal pattern of the tumor is shown in Fig. 2. No such relationship was found. In 16 patients with pheochromocytoma, increased plasma ANP level (mean 63.3 & 12.6 fmol/ml) declined after surgical removal of the tumor (mean 22.4 k 2.9 fmol/ml; p < 0.05) (Fig. 3). Simultaneously, a decrease of blood pressure and plasma catecholamines was observed (Table 11). Similarly, we did not find any correlation between plasma ANP and plasma catecholamines in the pheochromocytoma group. On the other hand, this group displayed a significant positive correlation between plasma ANP concentration and both systolic (r = 0.57, p < 0.01) and diastolic (r =0.56, p < 0.01) blood pressure and heart rate (r = 0.49, p < 0.05). In contrast to these results found in patients with pheochromocytoma, no correlations between plasma ANP and blood pressure or heart rate were observed in patients with essential hypertension or in the control group. DISCUSSION In the present study we have demonstrated increased plasma ANP concentration in patients with pheochromocytoma. Various mechanisms affecting the secretion of ANP could be involved in patients with pheochromocytoma. Noradrenaline and adrenaline released from the chromaffin tumor may directly induce ANP secretion via stimulation of a and fi adrenergic receptors. Data obtained by Tunny et al. support this suggestion [ 10,111. They found that noradrenaline and adrenaline infusions within the physiological dose range cause increase of plasma ANP levels in normal subjects and in patients with essential hypertension. They have postulated that this action is likely to be mediated by the stimulation of a-adrenergic receptors, because smaller doses of norepinephrine than those of epinephrine resulted in a respectively higher increase of plasma ANP. The importance of autonomic nervous system in the secretion of ANP is supported by the experiments of Petterson et al., who demonstrated that saline infusion did not induce the elevation of plasma ANP levels in the denervated rat model [171. It should be noted that various physiological properties of catecholamines-mainly the pressor action and the inotropic and chronotropic properties, may con-
ANP concentration in patients with pheochromocytoma m N A + A ( 1 ~ 1 3 ) m N A (n=13) increased increased
ANP 90
Blood Press Downloaded from informahealthcare.com by Ohio State University Libraries on 12/02/14 For personal use only.
80
159
m N A + A (n=l) normal
r
i-
Fig. 2. Plasma ANP concentration in relation to hormonal activity of the pheochromocytoma (NA-noradrelanine, adrenaline).
ANP 100
r
'L I
.
h
E
P
\
40
PCO.05 BEFORE
AFTER
A-
Table 11. Plasma A N P concentration, blood pressure, plasma and urinary catecholamine concentration in patients with pheochromocytoma before and after surgical treatment (2fSE)
SBP (mmHg) DBP (mmHg) "4 (pg/ml) A (pg/ml) UVNA(pg/24 h) u v A @d24 h) ANP (fmol/ml)
Before
After
P
141+5 93f4 892+ 191 188f26 588 f 287 13f3 63+13
122f8 81 f 3 321 f 12 69f5 19_+1 3fl 22f3
< 0.05 < 0.05
1992; 1: 157-161
Plasma Atrial Natriuretic Peptide (ANP) Concentration in Patients with Pheochromocytoma K. STEPNIAKOWSKI, A. JANUSZEWICZ, M. LAPINSKI, T. FELTYNOWSKI, J. CHODAKOWSKA, H. IGNATOWSKA-SWITALSKA, B. WOCIAL and W. JANUSZEWICZ From the Department of Hypertension and Angiology. Institute of Internal Medicine, Warsaw. Poland
Blood Press Downloaded from informahealthcare.com by Ohio State University Libraries on 12/02/14 For personal use only.
StepniakowskiK, Januszewicz A, Lapikki M, Feltywwski T, ChodakowskaJ, Ignatowska-Switalska H, Wocial B, Januszewicz W. Plasmaatrialnarriureticpeptide( A N P ) concentration inpatients wjth~heoc~romocytoma. Blood Pressure 1992; 1: 157-161. The interaction between catecholamines (CA) and ANP is not clearly established. The effects of excess endogenous CA on ANP secretion can be investigated in patients with pheochromocytorna. We studied 27 patients with surgically and histologically proven pheochromocytoma (P) aged 19-70 years. In 16 of these patients plasma ANP study was repeated after surgical removal of the tumour. The control group (C) consisted of 20 healthy volunteers aged 21-48 years. Moreover, 42 patients with uncomplicated mild to moderate essential hypertension (EH) aged 18-48 years were also studied. In P higher plasmaANPconcentrationversusC, EH wasfound(51.9f8.1;25.5+ 1.5; 19.3+ 1.5fmol/ml,respectively).In 16patients with P, increased plasma ANP level (mean 63.3 & 12.6 fmol/ml) declined after surgical removal of the tumour (mean 22.4+ 2.9 fmol/ ml). In the P patients no relationship was found between plasma ANP and hormonal patterns of the tumour or between plasma ANP and plasma catecholamines, whereas significant positive correlations between plasma ANP and both systolic and diastolic blood pressure and heart rate were demonstrated. These results suggest that excess CA produced by the chromaffin tumour induce ANP secretion via stimulation of adrenergic receptors. However, influence of the haemodynamic changes evoked by CA cannot be excluded. It is suggested that increased secretion of ANP may be of some importance in maintaining blood pressure homeostasis in patients with pheochromocytorna. Key words; pheochromocytoma, atrial narriuretic peptide, noradrenaline, adrenaline.
INTRODUCTION Atrial natriuretic peptide (ANP) is a hormone with natriuretic, diuretic and vasodilatory properties, produced by the heart [l, 21. The most potent stimulus for ANP secretion is the stretch of the atrium [3,4]. Some experimental and clinical data indicate that the sympathetic nervous system may also influence the secretion of ANP [5-121. However, the interaction between catecholamines (CA) and ANP is not clearly established [13,14]. Pheochromocytoma is a good model for investigating the effects of the excess of endogenous CA on ANP secretion. The aim of this study was therefore to determine plasma ANP concentration in patients with pheochromocytorna and to investigate the interrelationship between catecholamines and ANP.
MATERIAL AND METHODS We studied 27 patients (17 women and 10 men) with surgically and histologically proven pheochromocytoma, aged 19 to 70 years. Twelve of these patients had paroxysmal hypertension, and in 15 patients the hypertension was sustained. None had symptoms of catecholamine cardiomyopathy or heart failure. The control group consisted of 20 healthy normotensive volunteers (12 women and 8 men), aged 21 to 48 years. Moreover, 42 patients with uncomplicated, mild to moderate essential hypertension (1 1 women, 31 men), aged I8 to 46 years were studied.
The subjects were hospitalized and maintained on a diet with normal content of sodium and potassium; any drugs were withdrawn for a t least 2 weeks before the study. All participants gave informed consent to the investigations. On the morning of the study, following an overnight fast, and after the 24-h urine collection was started, the patients remained recumbent and a Teflon cannula was inserted into an antecubital vein. At least 30 min afterwards the blood pressure was measured with a mercury sphygmomanometer, the 5th Korotkoff's phase being taken for the diastolic cut-off point. Blood samples were drawn from the cannula immediately thereafter and were placed in chilled polypropylene tubes containing aprotonin and Na verseniane for determination of atrial natriuretic peptide (ANP). All samples were immediately centrifuged at +4°C and aliquots of plasma were frozen at - 20" C until assayed. ANP plasma concentration was determined by radioimmunoassay using Peninsula antibodies and Amersham iodinated ANP. Extraction of ANP from plasma was performed by means of SEPPACK C- I8 cartridges (Waters Associated, Milford, MA USA). Recovery after extraction was 88.4%, detection limit was 1 pg per tube, and interassay coefficient of variation was 6%. Plasma concentration of catecholamines was determined by radioenzymatic procedure using a commercial kit. Urinary excretion of catecholamines was determined by fluorometric methods [15, 161. In 16 of the patients with pheochromocytorna
158
K . Stepniakowski et al.
Table I. Plasma A N P concentration and blood pressure in patients with pheochromocytoma, essential hypertension and in the control group Zk SE are shown. The letters indicate significant differences between groups by Student's unpaired t-test. p < 0.05. a-P vs C, &P vs EH, C-EH vs C .
Blood Press Downloaded from informahealthcare.com by Ohio State University Libraries on 12/02/14 For personal use only.
SBP (mmHg) DBP (mmHg) ANP (fmol/ml)
P (n=27)
EH (n=42)
C (n=20)
139+6" 90 f4" 51.9+8.1ab
153k3' 92 k 2" 25.5k 1.5
118f2 71 1 2 19.3+ 1.5
plasma ANP study was repeated 2 weeks after surgical removal of the tumor. Statistical analysis was performed using Student's ttest for paired and non-paired data. Correlation coefficients were calculated by the least-squares method. Levels of significance were set at a p-value less than 0.05. RESULTS Blood pressure and plasma ANP concentration of the investigated groups of patients are shown in Table I. The mean plasma ANP concentration in patients with pheochromocytoma (P) was significantly higher in comparison with patients with essential hypertension (EH) and normotensive controls (C) (5 1.9f8.1, 25.5 f 1S, 19.3f 1.5 fmol/ml respectively; P vs EH p < 0.05; P vs C p < 0.05). No differencesinplasma ANP concentrations between patients with essential hypertension and normotensive controls were found (Fig. 1). It should be pointed out that in 8 pheochromocytoma patients plasma ANP concentration remained within the range of normotensive control values.
ANP 'O0
l'O
i
PHEO 11-27
EH 1-1-42
C n-20
0
t
j t t
f
Fig. 1. Plasma ANP concentrationin patients with pheochromocytoma (PHEO), essential hypertension ( E H ) and in the control group ( C ) .
Hormonal pattern of the tumors was established on the basis of urinary excretion of free noradrenaline and adrenaline. Thirteen patients excreted excessive amounts of both catecholamines; in another 13 cases we found only an increased excretion of NA, while in one patient urinary excretion of both NA and A was normal. Plasma ANP level in relation to the hormonal pattern of the tumor is shown in Fig. 2. No such relationship was found. In 16 patients with pheochromocytoma, increased plasma ANP level (mean 63.3 & 12.6 fmol/ml) declined after surgical removal of the tumor (mean 22.4 k 2.9 fmol/ml; p < 0.05) (Fig. 3). Simultaneously, a decrease of blood pressure and plasma catecholamines was observed (Table 11). Similarly, we did not find any correlation between plasma ANP and plasma catecholamines in the pheochromocytoma group. On the other hand, this group displayed a significant positive correlation between plasma ANP concentration and both systolic (r = 0.57, p < 0.01) and diastolic (r =0.56, p < 0.01) blood pressure and heart rate (r = 0.49, p < 0.05). In contrast to these results found in patients with pheochromocytoma, no correlations between plasma ANP and blood pressure or heart rate were observed in patients with essential hypertension or in the control group. DISCUSSION In the present study we have demonstrated increased plasma ANP concentration in patients with pheochromocytoma. Various mechanisms affecting the secretion of ANP could be involved in patients with pheochromocytoma. Noradrenaline and adrenaline released from the chromaffin tumor may directly induce ANP secretion via stimulation of a and fi adrenergic receptors. Data obtained by Tunny et al. support this suggestion [ 10,111. They found that noradrenaline and adrenaline infusions within the physiological dose range cause increase of plasma ANP levels in normal subjects and in patients with essential hypertension. They have postulated that this action is likely to be mediated by the stimulation of a-adrenergic receptors, because smaller doses of norepinephrine than those of epinephrine resulted in a respectively higher increase of plasma ANP. The importance of autonomic nervous system in the secretion of ANP is supported by the experiments of Petterson et al., who demonstrated that saline infusion did not induce the elevation of plasma ANP levels in the denervated rat model [171. It should be noted that various physiological properties of catecholamines-mainly the pressor action and the inotropic and chronotropic properties, may con-
ANP concentration in patients with pheochromocytoma m N A + A ( 1 ~ 1 3 ) m N A (n=13) increased increased
ANP 90
Blood Press Downloaded from informahealthcare.com by Ohio State University Libraries on 12/02/14 For personal use only.
80
159
m N A + A (n=l) normal
r
i-
Fig. 2. Plasma ANP concentration in relation to hormonal activity of the pheochromocytoma (NA-noradrelanine, adrenaline).
ANP 100
r
'L I
.
h
E
P
\
40
PCO.05 BEFORE
AFTER
A-
Table 11. Plasma A N P concentration, blood pressure, plasma and urinary catecholamine concentration in patients with pheochromocytoma before and after surgical treatment (2fSE)
SBP (mmHg) DBP (mmHg) "4 (pg/ml) A (pg/ml) UVNA(pg/24 h) u v A @d24 h) ANP (fmol/ml)
Before
After
P
141+5 93f4 892+ 191 188f26 588 f 287 13f3 63+13
122f8 81 f 3 321 f 12 69f5 19_+1 3fl 22f3
< 0.05 < 0.05
