Serum contains a potent factor that decreases β-adrenergic receptor-stimulated L-type Ca2+ current in cardiac myocytes

摘要: L-type Ca2+ current (ICa) was measured in cultured atrial myocytes from hearts of adult guinea-pigs using whole-cell voltage clamp. Potentiation ICa induced by β-adrenergic stimulation (isoprenaline 2· 10−7 M) could be completely antagonized diluted sera (1∶100 v/v). Half-maximal inhibition β-receptorstimulated occurred at about 1∶1000. Basal not affected serum. Atropine a concentration (10−6M) that the anti-adrenergic effect acetylcholine (ACh, 2·10−6 did interfere with In cells dialysed cyclic adenosine monophosphate (cAMP)-containing (10−4 pipette solution, potentiated insensitive to both ACh and Preincubation pertussis toxin almost abolished effects The potency serum reduced dialysis. It is concluded contains factor which, like ACh, inhibits β-receptor-stimulated adenylyl cyclase via Giprotein.