Effect of diamide on isolated guinea pig atria.
Diamide [(diazinedicarboxylic acid-bis (dimethylamide)] 50 micrograms/ml induced a positive inotropic and chronotropic effect on spontaneously beating atria from normal and reserpine pretreated guinea pigs and a positive inotropic action on electrically driven left atria. Cumulative addition of diamide 600 micrograms/ml caused a systolic standstill of atria. D(-) INPEA 2 micrograms/ml, a beta-adrenergic blocking agent, antagonized the positive chronotropic action of diamide 50 micrograms/ml while it did not affect the positive inotropic action caused by diamide. In isolated atria perfused with Ca2+ free medium and recovered by stepwise addition of calcium chloride, the calcium level required to restore normal activity was 1.04 mmol/1 while it was 0.52 mmol/l in the presence of diamide. Ruthenium red 10 micrograms/ml, a specific inhibitor of calcium transport in mitochondria, antagonized diamide-induced recovery of the cardiac activity in calcium poor medium. Two different mechanisms, that involve calcium movements and beta-receptor, have been proposed for diamide action on heart muscle.
D000818:Animals; D001391:Azo Compounds / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D003958:Diamide / Q000494:pharmacology*; D004558:Electric Stimulation; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D012430:Ruthenium Red / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000187:drug effects; D014439:Tyramine / Q000494:pharmacology
D001391:Azo Compounds; D003958:Diamide; D012430:Ruthenium Red; D002118:Calcium; D014439:Tyramine