Relaxant action produced by sodium nitroprusside in guinea-pig tracheal muscle.
Effects of sodium nitroprusside (SNP) on tension and cytosolic Ca2+ concentration ([Ca2+]i) in guinea-pig tracheal muscle were investigated by performing simultaneous tension/fura-2 signal measurement. Muscle tone was generated by exogeneous PGE2 in the presence of indomethacin and atropine. As observed in terbutaline-induced relaxation, SNP-induced relaxation was not significantly affected by the presence of verapamil and it was accompanied by a correlative decrease in [Ca2+]i. Exposed to cyclopiazonic acid, the relaxation and decrease in the fura-2 signal produced by SNP were attenuated in comparison with the responses to terbutaline. Further, relaxation produced by several cGMP-related agents was compared with that produced by several cAMP-related agents with regard to effects of CPA. In conclusion, lowering of [Ca2+]i seems to be the most essential factor for SNP-induced, as well as for terbutaline-induced, relaxation, and Ca2+ sequestration into the sacroplasmic reticulum is greatly responsible for cGMP-, especially for SNP-induced relaxation.
Ito
Y
Y
2nd Department of Internal Medicine, School of Medicine, Nagoya University, Japan. itoyasu@tsuru.med.nagoya-u.ac.jp
Yamaki
K
K
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D005260:Female; D016257:Fura-2 / Q000737:chemistry; D006168:Guinea Pigs; D007211:Indoles / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology*; D013726:Terbutaline / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects*; D014700:Verapamil / Q000494:pharmacology
D007211:Indoles; D009599:Nitroprusside; C016276:8-bromocyclic GMP; D001285:Atropine; D014700:Verapamil; D006152:Cyclic GMP; D015232:Dinoprostone; D013726:Terbutaline; D002118:Calcium; D016257:Fura-2; C000543:cyclopiazonic acid; D007213:Indomethacin