Adenylate cyclase activity in fetal rabbit myocardium.
Adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] was determined in vitro in fetal rabbit myocardial membranes from individual fetal pups at 21 to 31 days gestation (term, 31 days). Basal and NaF-stimulated adenylate cyclase activities did not change during 21-31 days gestation. Significant stimulation of the enzyme by l-isoproterenol was observed only in the presence of guanosine triphosphate (100 microM). Under these conditions, maximal adenylate cyclase stimulation by l-isoproterenol (100 microM) was significantly higher at 25-31 than at 21 days gestation. Moreover, EC50 (Kact) for l-isoproterenol at 25-31 days was significantly lower than at 21 days gestation. We conclude that, in fetal rabbit myocardial membranes, there is an increase in the sensitivity of adenylate cyclase stimulation by l-isoproterenol from 21 to 25-31 days gestation.
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D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D005260:Female; D005865:Gestational Age; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006321:Heart / Q000196:embryology*; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology*; D011247:Pregnancy; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000187:drug effects; D013268:Stimulation, Chemical
D011943:Receptors, Adrenergic, beta; D006160:Guanosine Triphosphate; D011433:Propranolol; D000262:Adenylyl Cyclases; D007545:Isoproterenol