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Differences between vasorelaxant responses of the canine and human mesenteric arteries and veins to amrinone
European Journal of Pharmacology, 218 (1992) 347-349 © 1992 Elsevier Science Publishers B.V. All rights reserved 0014-2999/92/$05.00
347
F_JP 21091
Short communication
Differences between vasorelaxant responses of the canine and human mesenteric arteries and veins to amrinone Haruki Itoh
a,
Yasuhiro Sato
a,
K o i c h i T a n i g u c h i a, H a r u t o N a k a g a w a b, J u n Inui b and Jugoro Takeuchi a
Second Department of Internal Medicine, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113, Japan and b Research Laboratories, Yoshitomi Pharmaceutical Industries Ltd., Koyata Iruma-shi, Saitama 358, Japan
a
Received 10 April 1992, accepted 26 May 1992
Amrinone induced similar degrees of relaxation in human mesenteric arteries and veins contracted with KC1, but exerted a more potent vasodilator effect in canine mesenteric veins than in arteries. Dibutyryl cAMP had a stronger effect on KCl-induced contraction in canine mesenteric veins than in arteries. These results suggest that amrinone promotes a different vasodilating action in human and canine mesenteric vessels, possibly via different sensitivity to cAMP in each vascular smooth muscle. Amrinone; Dibutyryl cAMP; Mesenteric artery; Mesenteric vein
1. Introduction
Recently, c A M P - p h o s p h o d i e s t e r a s e ( P D E ) inhibitors have been used in the treatment of heart failure as inodilators, which generate inotropic and vasodilating activities (Opie, 1986; Evans, 1989). Amrinone is one of first-line P D E inhibitor compounds which shows a confirmed positive inotropic and vasorelaxant effect in preclinical (Toda et al., 1984; Harris et al., 1989; Sys et al., 1987) and clinical studies (Mancini et al., 1985). Vasodilation is useful as an unloading therapy in patients with congestive heart failure. It is clinically important to evaluate which vascular bed, i.e. veins or arteries, a vasodilator preferentially affects, but little is known about the relative selectivity of amrinone for arteries and veins. We thus designed the present study so that we could examine the effect of amrinone on human and canine arteries and veins. We further studied the vasodilating actions of dibutyryl cAMP (DBcAMP) on human and canine mesenteric vessels.
resection. Mongrel dogs of either sex weighing 8-15 kg were anesthetized with an i.v. injection of sodium pentobarbital (30 mg/kg), and mesenteric arteries and veins were removed. The arteries and veins of both (0.5-1.0 mm outside diameter) were cut into rings approximately 4 mm long. The rings were fixed horizontally between hooks under a resting force of 0.5 g for veins and 1.0 g for arteries. KCI (15 mM in human mesenteric arteries and veins and 20 mM in canine mesenteric arteries and veins) and phenylephrine (10 -6 M) produced contractions of approximately 30% of the maximum contractions caused by norepinephrine (3 × 10 -5 M). The cumulative concentration-response curves for amrinone were then obtained. The relaxations induced by amrinone were calculated as a percentage of the maximum relaxation induced by 10 -4 M papaverine. The results given here are mean values + S.E.M. Analysis for statistical significance was carried out by means of paired and non-paired Student's t-test. Values of P < 0.05 were considered statistically significant. The drugs used were amrinone (Meiji Seika), DBcAMP (Daiichi) and diltiazem (Wako).
2. Materials and methods
H u m a n mesenteric arteries and veins were obtained at autopsy within 5 h after death or at surgery for colon
Correspondence to: H. Itoh, The Cardiovascular Institute Hospital, 7-3-10 Roppongi, Minato-ku, Tokyo 106, Japan. Tel. 81.3.3408 2151.
3. Results
To observe relaxation responses to amrinone, human mesenteric vessels (arteries and veins) were precontracted with 15 mM KCI and canine mesenteric vessels were precontracted with 20 mM KCL The abso-
348
lute values for the sustained contractions induced with KC1 were 0.76 + 0.13 g in human mesenteric arteries (n = 4), 0 . 5 2 _ 0.06 g in veins (n = 4), 0.96 + 0.17 g in canine mesenteric arteries (n = 9) and 0.62 + 0.09 g in veins (n = 9). KC1 produced contractions of 36.5% of the maximum contractions induced by norepinephrine (3 x 10 -5 M) in h u m a n mesenteric arteries, 35.5% in veins, 33.1% in canine mesenteric arteries and 31.3% in veins. Amrinone ( 1 0 - 7 - 3 x 10 -5 M) induced similar degrees of relaxation in human mesenteric arteries and veins contracted with 15 m M KCI (fig. 1). The IC50 values for relaxation in human tissues were 1.9 x 10 -5 M in mesenteric arteries and 1.7 x 10 -5 M in veins (n = 5). In canine mesenteric vessels precontracted with 20 m M KC1, amrinone showed a more potent vasodilating effect on veins than on arteries as shown in table 1 (n = 9, P < 0.01). Amrinone similarly had a more potent inhibitory effect on phenylephrine (10 -6 M)-induced contraction of canine mesenteric veins than arteries (n = 4, P < 0.01). D B c A M P also induced greater relaxation of phenylephrine-contracted canine mesenteric veins than arteries (n = 3, P < 0.05). On the other hand, diltiazem inhibited KCl-induced contractions in canine mesenteric arteries and veins equipotently, and
A) Human(n=5) lO0 -
E qa
- - - o - - ~
50
o u_
Vein
;
0
-8
-7
-6 -5 Amrinone (log M)
-4
-3
B) Canine (n=9) ~
100
~ o u_
50
_
0
_
,
-8
-7
.
~
i
_
~
,
-6 -5 Amrinone (log M)
,
-4
3
Fig. 1. Effect of amrinone on KCl-induced contraction in human mesenteric vessels (A) and in canine mesenteric vessels (B). S.E.M. is shown by the error bar only when it is greater than each symbol. The means_+ S.E.M. of the starting levels of force in human mesenteric arteries and veins were 1.04 5:0.17 and 0.56 _+0.07 g (n = 5) and those in canine mesenteric arteries and veins were 0.97_+ 0.02 and 0.50 5: 0.01 g (n = 9), respectively.
TABLE 1 ICs0 values for amrinone, DBcAMP (dibutyryl cAMP) and diltiazem on (A) KCI- and (B) phenylephrine-induced contraction in canine artery and vein. Means-+ S.E.M. are shown, and numbers in parenthesis indicate the number of experiments. ICs0(M) Artery
Vein
(A) KCl-induced contraction Amrinone DBcAMP Diltiazem
2.0+0.2x 10 -4 (9) > 10 3 (3) 6.0+ 1.1 × 10 7 (4)
1.6+0.2x10 5(9) 4.4_+ 1.9x 10 -4 (3) 5.3 5:2.8 x 10 -7 (4)
(B) Phenylephrine-induced contraction Amrinone DBcAMP
3.5 5:0.3 x 10- 5 (4) 1.25:0.3x10 3 (3)
1 . 2 +_0.5 x 10 - 5 ( 4 ) 2.4+1.2x 10 -4 (3)
the IC50 values for arteries and veins were not statistically different (n = 4).
4. Discussion In the present study, amrinone produced a vasorelaxant response to different extents in human and canine mesenteric vessels. We found that amrinone had a similar potent vasodilating action in human mesenteric arteries and veins. In contrast, after KCl-induced contraction, canine mesenteric veins were 13 times more sensitive to amrinone than were arteries. Similar effects of amrinone were observed on phenylephrine-induced contraction in canine mesenteric vessels. Pimobendan, a P D E inhibitor, shows a more potent vasorelaxant effect on mesenteric vein than on thoracic aorta in rat (Fujimoto and Matsuda, 1990). Amrinone is reported to exhibit positive inotropic and vasodilator effects and to inhibit the low K m cAMPspecific P D E ( P D E IIIc) of the sarcoplasmic reticulum (Kauffman et al., 1987). The IC50 values (12-35 ~ M ) for contractions due to amrinone in this study are similar to IC50 values for amrinone for inhibition of canine (28 /.~M), monkey (7 /xM) and guinea pig (8 /zM) vascular P D E IIIc (Silver, 1989). These results support the possibility that the vasorelaxant effect of amrinone on mesenteric vessels may be due to the increase in the cAMP content resulting from P D E inhibition in vascular smooth muscle cells. In canine mesenteric vascular vessels, DBcAMP, a stable cAMP derivative, which is capable of penetrating the membrane of smooth muscle ceils, showed a more potent effect on veins than on arteries. Furthermore, the vasorelaxant profile of amrinone was similar to that of the adenylate cyclase stimulator, isoproterenol (data not shown), but dissimilar from that of the Ca 2÷ antagonist, diltiazem. There are several possible subcellular mechanisms of action subsequent to cAMP formation that may
349
explain the vasorelaxant profile of amrinone: Ca 2÷ efflux, decrease in Ca 2+ sensitivity of contractile protein and sequestration of Ca 2÷ to intracellular storage sites (Meisheri et al., 1980). Further studies are required to clarify the precise mechanism of the response to amrinone. However, the sensitivity to cAMP of vascular smooth muscles may explain the difference in profiles of the vasorelaxant response between canine and human mesenteric vessels.
Acknowledgements We appreciate the excellent technical assistance of Ken Hiramatsu. We also thank Meiji Seika Kaisha Ltd., Japan, for kindly providing amrinone.
References Evans, D.B., 1989, Overview of cardiovascular physiologic and pharmacologic aspects of selective phosphodiesterase peak III inhibitors, Am. J. Cardiol. 63, 9A. Fujimoto, S. and T. Matsuda, 1990, Effects of pimobendan, a car-
diotonic and vasodilating agent with phosphodiesterase inhibiting properties, on isolated arteries and veins of rats, J. Pharmacol. Exp. Ther. 252, 1304. Harris, A.L., A.M. Grant, P.J. Silver, D.B. Evans and A.A. Alousi, 1989, Differential vasorelaxant effects of milrinone and amrinone on contractile responses of canine coronary, cerebral and renal arteries, J. Cardiovasc. Pharmacol. 13, 238. Kauffman, R.F., K.W. Schenck, B.G. Utterback, V.G. Crowe and M.L. Cohen, 1987, In vitro vascular relaxation by new inotropic agents: Relationship to phosphodiesterase inhibition and cyclic nucleotides, J. Pharmacol. Exp. Ther. 242, 864. Mancini, D., T. LeJemtel and E. Sonnenblick, 1985, Intravenous use of amrinone for the treatment of the failing heart, Am. J. Cardiol. 56, 8B. Meisheri, K.D., R.F. Palmer and C. Van Breemen, 1980, The effects of amrinone on contractility, C a 2+ uptake and cAMP in smooth muscle, Eur. J. Pharmacol. 61, 159. Opie, LH., 1986, Inodilators, Lancet 7, 1336. Silver, P.J., 1989, Biochemical aspects of inhibition of cardiovascular low (Km) cyclic adenosine monophosphate phosphodiesterase, Am. J. Cardiol. 63, 2A. Sys, S.U., P.J. Boels and D.L. Brutsaert, 1987, Positive inotropic and vasodilating effects of amrinone and milrinone in isolated canine heart, J. Cardiovasc. Pharmacol. 10, 445. Toda, N., M. Nakajima, K. Nishimura and M. Miyazaki, 1984, Responses of isolated dog arteries to amrinone, Cardiovasc. Res. 18, 174.
347
F_JP 21091
Short communication
Differences between vasorelaxant responses of the canine and human mesenteric arteries and veins to amrinone Haruki Itoh
a,
Yasuhiro Sato
a,
K o i c h i T a n i g u c h i a, H a r u t o N a k a g a w a b, J u n Inui b and Jugoro Takeuchi a
Second Department of Internal Medicine, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113, Japan and b Research Laboratories, Yoshitomi Pharmaceutical Industries Ltd., Koyata Iruma-shi, Saitama 358, Japan
a
Received 10 April 1992, accepted 26 May 1992
Amrinone induced similar degrees of relaxation in human mesenteric arteries and veins contracted with KC1, but exerted a more potent vasodilator effect in canine mesenteric veins than in arteries. Dibutyryl cAMP had a stronger effect on KCl-induced contraction in canine mesenteric veins than in arteries. These results suggest that amrinone promotes a different vasodilating action in human and canine mesenteric vessels, possibly via different sensitivity to cAMP in each vascular smooth muscle. Amrinone; Dibutyryl cAMP; Mesenteric artery; Mesenteric vein
1. Introduction
Recently, c A M P - p h o s p h o d i e s t e r a s e ( P D E ) inhibitors have been used in the treatment of heart failure as inodilators, which generate inotropic and vasodilating activities (Opie, 1986; Evans, 1989). Amrinone is one of first-line P D E inhibitor compounds which shows a confirmed positive inotropic and vasorelaxant effect in preclinical (Toda et al., 1984; Harris et al., 1989; Sys et al., 1987) and clinical studies (Mancini et al., 1985). Vasodilation is useful as an unloading therapy in patients with congestive heart failure. It is clinically important to evaluate which vascular bed, i.e. veins or arteries, a vasodilator preferentially affects, but little is known about the relative selectivity of amrinone for arteries and veins. We thus designed the present study so that we could examine the effect of amrinone on human and canine arteries and veins. We further studied the vasodilating actions of dibutyryl cAMP (DBcAMP) on human and canine mesenteric vessels.
resection. Mongrel dogs of either sex weighing 8-15 kg were anesthetized with an i.v. injection of sodium pentobarbital (30 mg/kg), and mesenteric arteries and veins were removed. The arteries and veins of both (0.5-1.0 mm outside diameter) were cut into rings approximately 4 mm long. The rings were fixed horizontally between hooks under a resting force of 0.5 g for veins and 1.0 g for arteries. KCI (15 mM in human mesenteric arteries and veins and 20 mM in canine mesenteric arteries and veins) and phenylephrine (10 -6 M) produced contractions of approximately 30% of the maximum contractions caused by norepinephrine (3 × 10 -5 M). The cumulative concentration-response curves for amrinone were then obtained. The relaxations induced by amrinone were calculated as a percentage of the maximum relaxation induced by 10 -4 M papaverine. The results given here are mean values + S.E.M. Analysis for statistical significance was carried out by means of paired and non-paired Student's t-test. Values of P < 0.05 were considered statistically significant. The drugs used were amrinone (Meiji Seika), DBcAMP (Daiichi) and diltiazem (Wako).
2. Materials and methods
H u m a n mesenteric arteries and veins were obtained at autopsy within 5 h after death or at surgery for colon
Correspondence to: H. Itoh, The Cardiovascular Institute Hospital, 7-3-10 Roppongi, Minato-ku, Tokyo 106, Japan. Tel. 81.3.3408 2151.
3. Results
To observe relaxation responses to amrinone, human mesenteric vessels (arteries and veins) were precontracted with 15 mM KCI and canine mesenteric vessels were precontracted with 20 mM KCL The abso-
348
lute values for the sustained contractions induced with KC1 were 0.76 + 0.13 g in human mesenteric arteries (n = 4), 0 . 5 2 _ 0.06 g in veins (n = 4), 0.96 + 0.17 g in canine mesenteric arteries (n = 9) and 0.62 + 0.09 g in veins (n = 9). KC1 produced contractions of 36.5% of the maximum contractions induced by norepinephrine (3 x 10 -5 M) in h u m a n mesenteric arteries, 35.5% in veins, 33.1% in canine mesenteric arteries and 31.3% in veins. Amrinone ( 1 0 - 7 - 3 x 10 -5 M) induced similar degrees of relaxation in human mesenteric arteries and veins contracted with 15 m M KCI (fig. 1). The IC50 values for relaxation in human tissues were 1.9 x 10 -5 M in mesenteric arteries and 1.7 x 10 -5 M in veins (n = 5). In canine mesenteric vessels precontracted with 20 m M KC1, amrinone showed a more potent vasodilating effect on veins than on arteries as shown in table 1 (n = 9, P < 0.01). Amrinone similarly had a more potent inhibitory effect on phenylephrine (10 -6 M)-induced contraction of canine mesenteric veins than arteries (n = 4, P < 0.01). D B c A M P also induced greater relaxation of phenylephrine-contracted canine mesenteric veins than arteries (n = 3, P < 0.05). On the other hand, diltiazem inhibited KCl-induced contractions in canine mesenteric arteries and veins equipotently, and
A) Human(n=5) lO0 -
E qa
- - - o - - ~
50
o u_
Vein
;
0
-8
-7
-6 -5 Amrinone (log M)
-4
-3
B) Canine (n=9) ~
100
~ o u_
50
_
0
_
,
-8
-7
.
~
i
_
~
,
-6 -5 Amrinone (log M)
,
-4
3
Fig. 1. Effect of amrinone on KCl-induced contraction in human mesenteric vessels (A) and in canine mesenteric vessels (B). S.E.M. is shown by the error bar only when it is greater than each symbol. The means_+ S.E.M. of the starting levels of force in human mesenteric arteries and veins were 1.04 5:0.17 and 0.56 _+0.07 g (n = 5) and those in canine mesenteric arteries and veins were 0.97_+ 0.02 and 0.50 5: 0.01 g (n = 9), respectively.
TABLE 1 ICs0 values for amrinone, DBcAMP (dibutyryl cAMP) and diltiazem on (A) KCI- and (B) phenylephrine-induced contraction in canine artery and vein. Means-+ S.E.M. are shown, and numbers in parenthesis indicate the number of experiments. ICs0(M) Artery
Vein
(A) KCl-induced contraction Amrinone DBcAMP Diltiazem
2.0+0.2x 10 -4 (9) > 10 3 (3) 6.0+ 1.1 × 10 7 (4)
1.6+0.2x10 5(9) 4.4_+ 1.9x 10 -4 (3) 5.3 5:2.8 x 10 -7 (4)
(B) Phenylephrine-induced contraction Amrinone DBcAMP
3.5 5:0.3 x 10- 5 (4) 1.25:0.3x10 3 (3)
1 . 2 +_0.5 x 10 - 5 ( 4 ) 2.4+1.2x 10 -4 (3)
the IC50 values for arteries and veins were not statistically different (n = 4).
4. Discussion In the present study, amrinone produced a vasorelaxant response to different extents in human and canine mesenteric vessels. We found that amrinone had a similar potent vasodilating action in human mesenteric arteries and veins. In contrast, after KCl-induced contraction, canine mesenteric veins were 13 times more sensitive to amrinone than were arteries. Similar effects of amrinone were observed on phenylephrine-induced contraction in canine mesenteric vessels. Pimobendan, a P D E inhibitor, shows a more potent vasorelaxant effect on mesenteric vein than on thoracic aorta in rat (Fujimoto and Matsuda, 1990). Amrinone is reported to exhibit positive inotropic and vasodilator effects and to inhibit the low K m cAMPspecific P D E ( P D E IIIc) of the sarcoplasmic reticulum (Kauffman et al., 1987). The IC50 values (12-35 ~ M ) for contractions due to amrinone in this study are similar to IC50 values for amrinone for inhibition of canine (28 /.~M), monkey (7 /xM) and guinea pig (8 /zM) vascular P D E IIIc (Silver, 1989). These results support the possibility that the vasorelaxant effect of amrinone on mesenteric vessels may be due to the increase in the cAMP content resulting from P D E inhibition in vascular smooth muscle cells. In canine mesenteric vascular vessels, DBcAMP, a stable cAMP derivative, which is capable of penetrating the membrane of smooth muscle ceils, showed a more potent effect on veins than on arteries. Furthermore, the vasorelaxant profile of amrinone was similar to that of the adenylate cyclase stimulator, isoproterenol (data not shown), but dissimilar from that of the Ca 2÷ antagonist, diltiazem. There are several possible subcellular mechanisms of action subsequent to cAMP formation that may
349
explain the vasorelaxant profile of amrinone: Ca 2÷ efflux, decrease in Ca 2+ sensitivity of contractile protein and sequestration of Ca 2÷ to intracellular storage sites (Meisheri et al., 1980). Further studies are required to clarify the precise mechanism of the response to amrinone. However, the sensitivity to cAMP of vascular smooth muscles may explain the difference in profiles of the vasorelaxant response between canine and human mesenteric vessels.
Acknowledgements We appreciate the excellent technical assistance of Ken Hiramatsu. We also thank Meiji Seika Kaisha Ltd., Japan, for kindly providing amrinone.
References Evans, D.B., 1989, Overview of cardiovascular physiologic and pharmacologic aspects of selective phosphodiesterase peak III inhibitors, Am. J. Cardiol. 63, 9A. Fujimoto, S. and T. Matsuda, 1990, Effects of pimobendan, a car-
diotonic and vasodilating agent with phosphodiesterase inhibiting properties, on isolated arteries and veins of rats, J. Pharmacol. Exp. Ther. 252, 1304. Harris, A.L., A.M. Grant, P.J. Silver, D.B. Evans and A.A. Alousi, 1989, Differential vasorelaxant effects of milrinone and amrinone on contractile responses of canine coronary, cerebral and renal arteries, J. Cardiovasc. Pharmacol. 13, 238. Kauffman, R.F., K.W. Schenck, B.G. Utterback, V.G. Crowe and M.L. Cohen, 1987, In vitro vascular relaxation by new inotropic agents: Relationship to phosphodiesterase inhibition and cyclic nucleotides, J. Pharmacol. Exp. Ther. 242, 864. Mancini, D., T. LeJemtel and E. Sonnenblick, 1985, Intravenous use of amrinone for the treatment of the failing heart, Am. J. Cardiol. 56, 8B. Meisheri, K.D., R.F. Palmer and C. Van Breemen, 1980, The effects of amrinone on contractility, C a 2+ uptake and cAMP in smooth muscle, Eur. J. Pharmacol. 61, 159. Opie, LH., 1986, Inodilators, Lancet 7, 1336. Silver, P.J., 1989, Biochemical aspects of inhibition of cardiovascular low (Km) cyclic adenosine monophosphate phosphodiesterase, Am. J. Cardiol. 63, 2A. Sys, S.U., P.J. Boels and D.L. Brutsaert, 1987, Positive inotropic and vasodilating effects of amrinone and milrinone in isolated canine heart, J. Cardiovasc. Pharmacol. 10, 445. Toda, N., M. Nakajima, K. Nishimura and M. Miyazaki, 1984, Responses of isolated dog arteries to amrinone, Cardiovasc. Res. 18, 174.