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  • Title: Serum contains a potent factor that decreases beta-adrenergic receptor-stimulated L-type Ca2+ current in cardiac myocytes.
    Author: Banach K, Bünemann M, Hüser J, Pott L.
    Journal: Pflugers Arch; 1993 May; 423(3-4):245-50. PubMed ID: 8391681.
    Abstract:
    L-type Ca2+ current (ICa) was measured in cultured atrial myocytes from hearts of adult guinea-pigs using whole-cell voltage clamp. Potentiation of ICa induced by beta-adrenergic stimulation (isoprenaline 2.10(-7) M) could be completely antagonized by diluted sera (1:100 v/v). Half-maximal inhibition of beta-receptor-stimulated ICa occurred at about 1:1000. Basal ICa was not affected by serum. Atropine in a concentration (10(-6) M) that completely antagonized the anti-adrenergic effect of acetylcholine (ACh, 2.10(-6) M) did not interfere with the effect of serum. In cells dialysed with cyclic adenosine monophosphate (cAMP)-containing (10(-4) M) pipette solution, potentiated ICa was insensitive to both ACh and serum. Preincubation of the myocytes with pertussis toxin almost completely abolished the anti-adrenergic effects of both ACh and serum. The potency of serum was not reduced by dialysis. It is concluded that serum contains a factor which, like ACh, inhibits beta-receptor-stimulated adenylyl cyclase via Gi-protein.
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