Inhibitory effect of sodium nitroprusside on the relaxing action of isoproterenol in isolated rat urinary bladder.
1. Isoproterenol caused relaxation of rat detrusor muscles contracted by electrical stimulations. Sodium nitroprusside (SNP) and methylene blue inhibited the relaxation induced by isoproterenol without affecting forskolin-induced relaxation. 2. In the presence of theophylline, zaprinast still potentiated isoproterenol-relaxation. In the presence of butoxamine, a selective beta 2-adrenoceptor inhibitor, but not metoprolol, a selective beta 1-adrenoceptor inhibitor, SNP still inhibited isoproterenol-relaxation. 3. SNP inhibited the relaxation to dobutamine, a beta 1-adrenoceptor agonist but not that to terbutaline, a beta 2-adrenoceptor agonist. The relaxation to dobutamine was also inhibited by methylene blue. Further, in the presence of theophylline, zaprinast still potentiated dobutamine-relaxation. 4. Isoproterenol increased tissue level of cGMP, which was inhibited by propranolol. 5. These results suggest a possibility that, in rat detrusor muscles, isoproterenol causes relaxation due to increases in the level of both cAMP and cGMP.
Department of Pharmacology, University of Hawaii, School of Medicine, Honolulu 96822.
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Satake
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Zhou
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Shibata
D000818:Animals; D006152:Cyclic GMP / Q000032:analysis; D004280:Dobutamine / Q000494:pharmacology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000037:antagonists & inhibitors*; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000187:drug effects; D001743:Urinary Bladder / Q000187:drug effects* / Q000502:physiology
D011943:Receptors, Adrenergic, beta; D009599:Nitroprusside; D004280:Dobutamine; D006152:Cyclic GMP; D007545:Isoproterenol; D008751:Methylene Blue