Acta Physiol Scarzd 1991, 142, 77-82
Effects of selective phosphodiesterase inhibitors on isolated coronary, lung and renal arteries from man and rat S. L I N D G R E N and K.-E. ANDERSSON Department of Clinical Pharmacology, University Hospital, Lund, Sweden LINDGREN, S. and ANDERSON, K.-E. 1991. Effects of selective phosphodiesterase inhibitors on isolated coronary, lung and renal arteries from man and rat. Acta Physioi Scand 142, 77-82. Received 1 November 1990, accepted 17 December 1990. ISSN 0001-6772, Department of Clinical Pharmacology, Lund University Hospital, Lund, Sweden. The relaxant effects of some isozyme-selective phosphodiesterase inhibitors were evaluated in isolated human and rat coronary, lung and renal arteries. Milrinone and OPC 391 1, inhibitors of a cGMP-inhibited cAMP phosphodiesterase (cGI-PDE), were shown to have distinct vasodilator actions. These agents were less potent as relaxants in rat lung and renal arteries than in the corresponding human tissues. OPC 391 1, the more potent cGMP-inhibited cAMP phosphodiesterase inhibitor, was found to be the more potent vasorelaxant. Rolipram, a selective inhibitor of a cGMPnoninhibited cAMP phosphodiesterase, had small effects on coronary and lung arteries, but produced a slightly more pronounced relaxation of renal arteries from both man and rat. In human preparations contracted by 30 mM K', milrinone and OPC 3911 had similar relaxant profiles, and were as potent in coronary as in renal arteries. These results do not support the notion that milrinone has reduced effects on renal vessels in man and show that there may be species differences in vascular responsiveness to cGMP-inhibited cAMP phosphodiesterase inhibitors.
Key words: Milrinone; OPC 391 1 ; rolipram; vascular smooth muscle; human arteries; rat arteries.
Heart failure is often associated with an increased peripheral vascular resistance due to activation of the adrenergic nervous and the reninangiotensin systems. This vasoconstriction serves to redistribute blood flow away from some regions, e.g., kidneys, splanchnic beds, and skeletal muscle. A new generation of cardiotonic agents has been shown to exhibit positive inotropic actions as well as peripheral vasorelaxant effects (Colucci et al. 1986, Evans 1989, v. der Leyen 1989). These drugs have been demonstrated to selectively inhibit a cGMPinhibited low K , cAMP phosphodiesterase (cG1-PDE; Beavo 1988). Correspondence : Sam Lindgren, Department of Clinical Pharmacology, University Hospital, S-221 85 Lund, Sweden.
T h e vasorelaxant effects of cGI-PDE inhibitors do not seem to have been studied extensively in human vessels. A recent in v i t r o study on canine vessels showed a reduced effect of both amrinone and milrinone on renal arteries compared with coronary vessels (Harris et al. 1989). Thus, it may be of clinical interest to study the actions of cGI-PDE inhibitors on human arteries obtained from different vascular regions with special attention to renal arteries. I n the present study we examined the relaxant effects of milrinone and OPC 3911 in isolated human coronary, lung, and renal arteries. T h e latter compound has been shown to be the most potent of a series of selective inhibitors of the cGI-PDE (Degerman et al. 1987). In addition, the actions of rolipram, an antidepressant agent (Horowski et al. 1985) selectively inhibiting a
77
78
S. Lindgren and K.-E. Andersson
baths containing 5 ml of gassed (9.59,) O,, So/;, CO,) Krebs solution of the following composition (mM): NaCl 119, NaHCO, 15, KCI 4.6, CaCI, 1.5, NaH,PO, 1.2, MgCI, 1.2 and glucose 11 (pH % 7.4). Isometric tension was measured by a Grass Instrument FT 03 C transducer connected to a Grass Instrument model 7D polygraph. T h e arterial rings were allowed to equilibrate for 0.5 h (rat) or 1-2 h (man) with repeated washings (every 15 min). The initial mounting tension was readjusted until a stable tension was maintained. In human arterial rings this tension was 8 m N (coronary and renal) or 2 mN (lung), in rat preparations 1.5 m N (coronary and lung) or 3 m N MATERI.%I,S AND M E T H O D S (renal). At these tensions optimum contractile reTissues. Epicardial coronary arteries were obtained sponses were obtained, as determined in separate post mortem from five adults (four men, one woman, experiments. median age hh years) within 6 h of death. In two cases Erperimental procedure. After the equilibration death was caused b!- intra-abdominal disorders, and in period, the tissues were initially contracted by one case it was due to a traffic accident. Two patients, exposure to a high 124 mM K'-solution which was M ho died after coronary by pass operation. were on prepared by substituting all NaCl in the standard multiple drug therapj- while the other three were free Krebs solution with equimolar concentrations of KCI. from chronic drug treatment. Human lung tissue was Only arterial rings in which reproducible contractions obtained from 14 patients (10 men, four u-omen, (variation < loo/,) could be induced by 124 mM K' median age 58 years) undergoing surgery due to lung were accepted for the experiments. cancer. The patients did not take any drugs on a Human arterial segments from all three regions regular basis. Slices of human kidneys were obtained were contracted by 30 mM K'. Separate studies had from 13 patients (nine men, four women, median age shown that the phosphodiesterase inhibitors had 62 !ears) operated upon because of renal cancer. Four reduced relaxant effects if higher concentrations of patients were hypertensive ; three patients were on K' were used (Lindgren et ul. 1989). I n rat vessels thiazide diuretics and one patient was treated with 30 mci K- caused variable contractile responses, and atenolol. in renal preparations the contractions were not stable. The human preparations were taken from macroTherefore, 30 mM K' was not used to contract rat scopicall>-normal tissue. The!- were placed in chilled vessels. Krebs solution, and immediately transported to the The other contractile agonists were chosen after laborator>-. Male Sprague-Dadey rats (1 50-250 g, pilot studies had shown that they produced stable Xfnllegaard Breeding Center L T D , Denmark) were contractions in arterial rings from the different vascular sacrificed b!- cervical dislocation. T h e heart, the left regions. In all arteries a cumulative concentrationkidnel- and the lungs were rapidly removed. response curve was initially obtained for PGF,,, Pirsixlar preparation. The arteries were dissected serotonin or noradrenaline and the concentrations of out under a microscope and carefully trimmed free of the agonists that caused approximately 75 yo of the adhering fat and connective tissue. The human maximal response were determined. In vessels from coronar!., lung, and renal arteries had an outer man. the concentrations of PGF,, inducing the desired diameter in sztu of approximately 1.0 mm, 0.9 mm and contractions were 5 //M in coronary arteries and 3 ,UM 0.9 mm, respectively. The arteries used in the rat were (median value, range 1-5 ~ L Min) lung arteries, whereas the proximal part of the left anterior descending the concentration of noradrenaline in renal arteries coronar!. artery ( 20.3 mm), the second branch of the was 1 ,MM (mcdian value, range 0.3-3 p ~ )Diltiazem . main pulmonar!- artery ( 20.7 mm), and the second 1 p M was present in the experiments with human branch of the left renal artery ( % 0.4 mm). coronary- arteries to avoid problems with excessive The human arteries were either used immediately oscillations (Ramagopal et al. 1988). In rat vessels, the or stored in Krebs solution at 8 to 12 "C for no longer thus determined concentration of serotonin was 3 p~ than 24 h. Preparations thus stored did not differ in in coronary arteries and the concentrations of northeir responses to drugs from those used at once. T h e adrenaline were 0.1 ,UMand 1 ,LiM in lung and renal arteries, respectively. After a period of repeated rat arteries were used immediatelj-. Rtrording o f mechanical actirity. Tension studies washings (0.551 h). agonists at these concentrations were subsequently used to elicit contractions. When were performed as previously described (Hogestatt Z I the contraction had stabilized a relaxant concentration01. 1983). Briefly, ring segments 1-2 mm in length were mounted between two L-shaped metal holders response curve was obtained by cumulative addition immersed in temperature-controlled (37 "C) organ of a phosphodiesterase inhibitor. Control measure-
cGMP-non-inhibited low K,, CAMP phosphodiesterase (RI-PDE ; Beavo 1988) were studied. As it has been suggested that there exists a species variability in inotropic responsiveness to inhibitors of the c G I - P D E (Weishaar et a(. 1987), the relaxant effects of milrinone and OPC 391 1 were investigated in rat arteries to examine if such species differences exist also in vascular smooth muscle.
Vascular efects of selective PDE-inhibitors ments of vehicle effects were performed on separate arterial rings. Drugs. L-noradrenaline HCI (Nova-kemi) was dissolved in 0.9O/, NaCl containing 0.1 mM ascorbic acid. PGF,, was supplied as an aqueous solution (Amoglandin%, Astra), serotonin (S-hydroxytryptaminecreatinine sulphate, Sigma), and diltiazem HCI (Fcrrosan) was dissolved in distilled water. Milrinone (Sterling-Winthrop Research Institute) solution was prepared by dissolving 21.1 mg in 100pl 1 M HCI and diluting to 10 ml with distilled water. OPC 3911 (Otsuka Pharmaceuticals) was dissolved in 99.5% ethanol and rolipram (Schering) in 70% ethanol. Vehicle controls were prepared similarly without the drug. Stock solutions of the drugs (10 mM) were stored at -70 "C and fresh dilutions were made on the day of experiment. Statzsttcs. Relaxation was expressed as a percentage of the maximum relaxation of induced contractions i.e., back to baseline. If a spontaneous relaxation occurred in control tissues, the amount of relaxation observed was subtracted from the drug induced response. EC,, values (concentrations producing 50% relaxation of maximum contraction) were determined graphically. Student's t-test (two-tailed) and one-way analysis of variance followed by Newman-Keuls' test were employed to compare the log transformed EC,, values (from two and three groups, respectively). Differences were considered significant at P < 0.05. If the mean relaxation observed for a drug was less than 50 yo,the maximal relaxation obtained was reported. When the mean relaxation for a drug was more than 5006, but reduced relaxant effects were noted in some experiments, the EC,,, value was calculated by linear interpolation following the probit method and linearregression analysis. The EC,, values are expressed as geometric means and their 95 yo confidence intervals. Data are otherwise given as the meanFSEM; n denotes the number of arterial rings examined (from a minimum of four donors/rats).
79
55 %, respectively. I f the initial isometric force was compared instead, this was quite similar in coronary and renal arterial segments while it was only half as large in lung arterial rings (Table 1). Relaxant efiects Comparison of regional effects using 30 mM Ktcontracted human arterial rings. Milrinone and
OPC 391 1 had concentration-dependent relaxant effects on coronary, lung, and renal arterial tissues contracted by 30 mM Kt.Each drug was equipotent against 30 mM K+-induced contractions in coronary and renal arterial rings but did not produce 50% relaxation in lung arterial Table 1. Contractile effects* of K+, PGF,, and noradrenaline
Man K+ 124 mM K+ 30 mM PGF,,t Noradrenalinet Rat K' 124 mM Serotonin? PGF,,t Noradrenalinet
Coronary Lung arteries arteries
Renal arteries
8.4f 0.9 5.3 k0.3 6.3 f0.9 3.3f0.2 5.6k 0.7 3.9 0.4
11.1f1.2 6.2 k 0.3
-
1.6k0.1 3.7 & 0.3 1.3f0.1 2.0f0. 1 ~
-
-
10.3k 1.7
~
-
4.9f0.4 -
5.1k0.3
* Increase in tension (expressed in mN ; means f SEM). At a concentration generating t approximately 75 yo of maximal contraction produced by cumulative addition of agonist.
RESULTS Contractile responses I n preparations from both man and rat the magnitude of the contractions depended on from which vascular region the examined artery was taken (Table 1). 3 0 m M K + was used as contractile agent to facilitate comparisons of relaxant responses among arterial rings from the different human vascular regions. I f the 30 mM K+ induced contractions were expressed as percentage of the 124 mM Kt contractions in the coronary, lung, and renal arterial rings, the responses were approximately 75%, 60%, and
i00l. ' l o 8 10.'
'
m6 l o 5
l o 0 10' l o 6 l o 5
Concentration ( M
l o 8 10.'
l o 6 105
)
Fig. 1. Cumulative concentration-response curves for milrinone (a), OPC 391 1 (b), and rolipram (c) obtained in human coronary ( O ) ,lung (A), and renal (0) arteries contracted by 30 mM K'. Data are expressed as a percentage of the maximum possible relaxation (back to baseline) and represent the rnean_+SEM.
S . Lindgren nnd K.-E. Andersson
80
Table 2. Relaxant effects of milrinone, OPC 391 I , and rolipram on 30 mhi I(--contracted human coronary,
lung, and renal arterial rings EC,,, (9j0, C.I.) ( p i ) *
Loronar! Clilrinone OPC 3911 Rolipram
I.ung
I1
-
~
-/
1 7 (0 .i94.7) 1 4 (0 20-10) Oo,, at 30 j c w t
_
41",
~
at 30//41t 4Lo, at 30 put j o , at 3 0 p t
6 3
Renal
n _
_
~ ~ ~
12 12 6
~~ _
_
_
_
_
_
~_ ~
3 2 (1.2-8.1) 0.87 (0.2C3.0) 3 j 0 0 at 3 0 , u M t
~
_
n
_
12 12 9
EC,,, concentrations causing 5O0, relaxation ; C.I., confidence intervals. * \leans with associated 95 oo confidence intervals .\gent failed to produce jO",, relaxation.
+
,
., ..
.;'
. C ~
.
~
h3 3 -
.ae
I 175
.;P
as relaxants in human lung and renal arterial preparations than in the corresponding rat tissues (Table 3). No attempts were made to compare the relaxant effects observed in coronary arterial segments since different contractile agonists were used in tissues from man and rat. Rolipram had slight effects on coronary and lung arterial segments from man and rat but shoued a somewhat more pronounced relaxant activity in renal arterial rings from both species (Fig. 2 ) . There was not any significant species diflerence in relaxant effect of rolipram in lung and renal arterial preparations (Table 3). ,g.
.cF
.c5
Concentration I M 1
DISCUSSION
Fig. 2.
Effects of selective phosphodiesterase inhibitors on isolated coronary, lung and renal arteries from man and rat S. L I N D G R E N and K.-E. ANDERSSON Department of Clinical Pharmacology, University Hospital, Lund, Sweden LINDGREN, S. and ANDERSON, K.-E. 1991. Effects of selective phosphodiesterase inhibitors on isolated coronary, lung and renal arteries from man and rat. Acta Physioi Scand 142, 77-82. Received 1 November 1990, accepted 17 December 1990. ISSN 0001-6772, Department of Clinical Pharmacology, Lund University Hospital, Lund, Sweden. The relaxant effects of some isozyme-selective phosphodiesterase inhibitors were evaluated in isolated human and rat coronary, lung and renal arteries. Milrinone and OPC 391 1, inhibitors of a cGMP-inhibited cAMP phosphodiesterase (cGI-PDE), were shown to have distinct vasodilator actions. These agents were less potent as relaxants in rat lung and renal arteries than in the corresponding human tissues. OPC 391 1, the more potent cGMP-inhibited cAMP phosphodiesterase inhibitor, was found to be the more potent vasorelaxant. Rolipram, a selective inhibitor of a cGMPnoninhibited cAMP phosphodiesterase, had small effects on coronary and lung arteries, but produced a slightly more pronounced relaxation of renal arteries from both man and rat. In human preparations contracted by 30 mM K', milrinone and OPC 3911 had similar relaxant profiles, and were as potent in coronary as in renal arteries. These results do not support the notion that milrinone has reduced effects on renal vessels in man and show that there may be species differences in vascular responsiveness to cGMP-inhibited cAMP phosphodiesterase inhibitors.
Key words: Milrinone; OPC 391 1 ; rolipram; vascular smooth muscle; human arteries; rat arteries.
Heart failure is often associated with an increased peripheral vascular resistance due to activation of the adrenergic nervous and the reninangiotensin systems. This vasoconstriction serves to redistribute blood flow away from some regions, e.g., kidneys, splanchnic beds, and skeletal muscle. A new generation of cardiotonic agents has been shown to exhibit positive inotropic actions as well as peripheral vasorelaxant effects (Colucci et al. 1986, Evans 1989, v. der Leyen 1989). These drugs have been demonstrated to selectively inhibit a cGMPinhibited low K , cAMP phosphodiesterase (cG1-PDE; Beavo 1988). Correspondence : Sam Lindgren, Department of Clinical Pharmacology, University Hospital, S-221 85 Lund, Sweden.
T h e vasorelaxant effects of cGI-PDE inhibitors do not seem to have been studied extensively in human vessels. A recent in v i t r o study on canine vessels showed a reduced effect of both amrinone and milrinone on renal arteries compared with coronary vessels (Harris et al. 1989). Thus, it may be of clinical interest to study the actions of cGI-PDE inhibitors on human arteries obtained from different vascular regions with special attention to renal arteries. I n the present study we examined the relaxant effects of milrinone and OPC 3911 in isolated human coronary, lung, and renal arteries. T h e latter compound has been shown to be the most potent of a series of selective inhibitors of the cGI-PDE (Degerman et al. 1987). In addition, the actions of rolipram, an antidepressant agent (Horowski et al. 1985) selectively inhibiting a
77
78
S. Lindgren and K.-E. Andersson
baths containing 5 ml of gassed (9.59,) O,, So/;, CO,) Krebs solution of the following composition (mM): NaCl 119, NaHCO, 15, KCI 4.6, CaCI, 1.5, NaH,PO, 1.2, MgCI, 1.2 and glucose 11 (pH % 7.4). Isometric tension was measured by a Grass Instrument FT 03 C transducer connected to a Grass Instrument model 7D polygraph. T h e arterial rings were allowed to equilibrate for 0.5 h (rat) or 1-2 h (man) with repeated washings (every 15 min). The initial mounting tension was readjusted until a stable tension was maintained. In human arterial rings this tension was 8 m N (coronary and renal) or 2 mN (lung), in rat preparations 1.5 m N (coronary and lung) or 3 m N MATERI.%I,S AND M E T H O D S (renal). At these tensions optimum contractile reTissues. Epicardial coronary arteries were obtained sponses were obtained, as determined in separate post mortem from five adults (four men, one woman, experiments. median age hh years) within 6 h of death. In two cases Erperimental procedure. After the equilibration death was caused b!- intra-abdominal disorders, and in period, the tissues were initially contracted by one case it was due to a traffic accident. Two patients, exposure to a high 124 mM K'-solution which was M ho died after coronary by pass operation. were on prepared by substituting all NaCl in the standard multiple drug therapj- while the other three were free Krebs solution with equimolar concentrations of KCI. from chronic drug treatment. Human lung tissue was Only arterial rings in which reproducible contractions obtained from 14 patients (10 men, four u-omen, (variation < loo/,) could be induced by 124 mM K' median age 58 years) undergoing surgery due to lung were accepted for the experiments. cancer. The patients did not take any drugs on a Human arterial segments from all three regions regular basis. Slices of human kidneys were obtained were contracted by 30 mM K'. Separate studies had from 13 patients (nine men, four women, median age shown that the phosphodiesterase inhibitors had 62 !ears) operated upon because of renal cancer. Four reduced relaxant effects if higher concentrations of patients were hypertensive ; three patients were on K' were used (Lindgren et ul. 1989). I n rat vessels thiazide diuretics and one patient was treated with 30 mci K- caused variable contractile responses, and atenolol. in renal preparations the contractions were not stable. The human preparations were taken from macroTherefore, 30 mM K' was not used to contract rat scopicall>-normal tissue. The!- were placed in chilled vessels. Krebs solution, and immediately transported to the The other contractile agonists were chosen after laborator>-. Male Sprague-Dadey rats (1 50-250 g, pilot studies had shown that they produced stable Xfnllegaard Breeding Center L T D , Denmark) were contractions in arterial rings from the different vascular sacrificed b!- cervical dislocation. T h e heart, the left regions. In all arteries a cumulative concentrationkidnel- and the lungs were rapidly removed. response curve was initially obtained for PGF,,, Pirsixlar preparation. The arteries were dissected serotonin or noradrenaline and the concentrations of out under a microscope and carefully trimmed free of the agonists that caused approximately 75 yo of the adhering fat and connective tissue. The human maximal response were determined. In vessels from coronar!., lung, and renal arteries had an outer man. the concentrations of PGF,, inducing the desired diameter in sztu of approximately 1.0 mm, 0.9 mm and contractions were 5 //M in coronary arteries and 3 ,UM 0.9 mm, respectively. The arteries used in the rat were (median value, range 1-5 ~ L Min) lung arteries, whereas the proximal part of the left anterior descending the concentration of noradrenaline in renal arteries coronar!. artery ( 20.3 mm), the second branch of the was 1 ,MM (mcdian value, range 0.3-3 p ~ )Diltiazem . main pulmonar!- artery ( 20.7 mm), and the second 1 p M was present in the experiments with human branch of the left renal artery ( % 0.4 mm). coronary- arteries to avoid problems with excessive The human arteries were either used immediately oscillations (Ramagopal et al. 1988). In rat vessels, the or stored in Krebs solution at 8 to 12 "C for no longer thus determined concentration of serotonin was 3 p~ than 24 h. Preparations thus stored did not differ in in coronary arteries and the concentrations of northeir responses to drugs from those used at once. T h e adrenaline were 0.1 ,UMand 1 ,LiM in lung and renal arteries, respectively. After a period of repeated rat arteries were used immediatelj-. Rtrording o f mechanical actirity. Tension studies washings (0.551 h). agonists at these concentrations were subsequently used to elicit contractions. When were performed as previously described (Hogestatt Z I the contraction had stabilized a relaxant concentration01. 1983). Briefly, ring segments 1-2 mm in length were mounted between two L-shaped metal holders response curve was obtained by cumulative addition immersed in temperature-controlled (37 "C) organ of a phosphodiesterase inhibitor. Control measure-
cGMP-non-inhibited low K,, CAMP phosphodiesterase (RI-PDE ; Beavo 1988) were studied. As it has been suggested that there exists a species variability in inotropic responsiveness to inhibitors of the c G I - P D E (Weishaar et a(. 1987), the relaxant effects of milrinone and OPC 391 1 were investigated in rat arteries to examine if such species differences exist also in vascular smooth muscle.
Vascular efects of selective PDE-inhibitors ments of vehicle effects were performed on separate arterial rings. Drugs. L-noradrenaline HCI (Nova-kemi) was dissolved in 0.9O/, NaCl containing 0.1 mM ascorbic acid. PGF,, was supplied as an aqueous solution (Amoglandin%, Astra), serotonin (S-hydroxytryptaminecreatinine sulphate, Sigma), and diltiazem HCI (Fcrrosan) was dissolved in distilled water. Milrinone (Sterling-Winthrop Research Institute) solution was prepared by dissolving 21.1 mg in 100pl 1 M HCI and diluting to 10 ml with distilled water. OPC 3911 (Otsuka Pharmaceuticals) was dissolved in 99.5% ethanol and rolipram (Schering) in 70% ethanol. Vehicle controls were prepared similarly without the drug. Stock solutions of the drugs (10 mM) were stored at -70 "C and fresh dilutions were made on the day of experiment. Statzsttcs. Relaxation was expressed as a percentage of the maximum relaxation of induced contractions i.e., back to baseline. If a spontaneous relaxation occurred in control tissues, the amount of relaxation observed was subtracted from the drug induced response. EC,, values (concentrations producing 50% relaxation of maximum contraction) were determined graphically. Student's t-test (two-tailed) and one-way analysis of variance followed by Newman-Keuls' test were employed to compare the log transformed EC,, values (from two and three groups, respectively). Differences were considered significant at P < 0.05. If the mean relaxation observed for a drug was less than 50 yo,the maximal relaxation obtained was reported. When the mean relaxation for a drug was more than 5006, but reduced relaxant effects were noted in some experiments, the EC,,, value was calculated by linear interpolation following the probit method and linearregression analysis. The EC,, values are expressed as geometric means and their 95 yo confidence intervals. Data are otherwise given as the meanFSEM; n denotes the number of arterial rings examined (from a minimum of four donors/rats).
79
55 %, respectively. I f the initial isometric force was compared instead, this was quite similar in coronary and renal arterial segments while it was only half as large in lung arterial rings (Table 1). Relaxant efiects Comparison of regional effects using 30 mM Ktcontracted human arterial rings. Milrinone and
OPC 391 1 had concentration-dependent relaxant effects on coronary, lung, and renal arterial tissues contracted by 30 mM Kt.Each drug was equipotent against 30 mM K+-induced contractions in coronary and renal arterial rings but did not produce 50% relaxation in lung arterial Table 1. Contractile effects* of K+, PGF,, and noradrenaline
Man K+ 124 mM K+ 30 mM PGF,,t Noradrenalinet Rat K' 124 mM Serotonin? PGF,,t Noradrenalinet
Coronary Lung arteries arteries
Renal arteries
8.4f 0.9 5.3 k0.3 6.3 f0.9 3.3f0.2 5.6k 0.7 3.9 0.4
11.1f1.2 6.2 k 0.3
-
1.6k0.1 3.7 & 0.3 1.3f0.1 2.0f0. 1 ~
-
-
10.3k 1.7
~
-
4.9f0.4 -
5.1k0.3
* Increase in tension (expressed in mN ; means f SEM). At a concentration generating t approximately 75 yo of maximal contraction produced by cumulative addition of agonist.
RESULTS Contractile responses I n preparations from both man and rat the magnitude of the contractions depended on from which vascular region the examined artery was taken (Table 1). 3 0 m M K + was used as contractile agent to facilitate comparisons of relaxant responses among arterial rings from the different human vascular regions. I f the 30 mM K+ induced contractions were expressed as percentage of the 124 mM Kt contractions in the coronary, lung, and renal arterial rings, the responses were approximately 75%, 60%, and
i00l. ' l o 8 10.'
'
m6 l o 5
l o 0 10' l o 6 l o 5
Concentration ( M
l o 8 10.'
l o 6 105
)
Fig. 1. Cumulative concentration-response curves for milrinone (a), OPC 391 1 (b), and rolipram (c) obtained in human coronary ( O ) ,lung (A), and renal (0) arteries contracted by 30 mM K'. Data are expressed as a percentage of the maximum possible relaxation (back to baseline) and represent the rnean_+SEM.
S . Lindgren nnd K.-E. Andersson
80
Table 2. Relaxant effects of milrinone, OPC 391 I , and rolipram on 30 mhi I(--contracted human coronary,
lung, and renal arterial rings EC,,, (9j0, C.I.) ( p i ) *
Loronar! Clilrinone OPC 3911 Rolipram
I.ung
I1
-
~
-/
1 7 (0 .i94.7) 1 4 (0 20-10) Oo,, at 30 j c w t
_
41",
~
at 30//41t 4Lo, at 30 put j o , at 3 0 p t
6 3
Renal
n _
_
~ ~ ~
12 12 6
~~ _
_
_
_
_
_
~_ ~
3 2 (1.2-8.1) 0.87 (0.2C3.0) 3 j 0 0 at 3 0 , u M t
~
_
n
_
12 12 9
EC,,, concentrations causing 5O0, relaxation ; C.I., confidence intervals. * \leans with associated 95 oo confidence intervals .\gent failed to produce jO",, relaxation.
+
,
., ..
.;'
. C ~
.
~
h3 3 -
.ae
I 175
.;P
as relaxants in human lung and renal arterial preparations than in the corresponding rat tissues (Table 3). No attempts were made to compare the relaxant effects observed in coronary arterial segments since different contractile agonists were used in tissues from man and rat. Rolipram had slight effects on coronary and lung arterial segments from man and rat but shoued a somewhat more pronounced relaxant activity in renal arterial rings from both species (Fig. 2 ) . There was not any significant species diflerence in relaxant effect of rolipram in lung and renal arterial preparations (Table 3). ,g.
.cF
.c5
Concentration I M 1
DISCUSSION
Fig. 2.
