Apamin, a highly potent fetal L-type Ca2+ current blocker in single heart cells.
Apamin, a bee venom polypeptide, was reported to block the naturally occurring Ca2+ slow action potentials (APs) in cultured cell reaggregates from old chick hearts [Bkaily, G. et al. Am. J. Physiol. 248 (Heart Circ. Physiol. 17): H961-H965, 1985] as well as the tetrodotoxin (TTX)- and Mn(2+)-insensitive slow Na+ current in young embryonic chick heart cells (Bkaily, G. In Vitro Toxicology. Academic, In press; Bkaily et al. J. Mol. Cell. Cardiol. 23: 25-39, 1991). With the use of the whole cell voltage-clamp technique in single ventricular cells from 10-day-old chick embryos and 17- to 20-wk-old human fetuses, two types of Ca2+ currents (ICa), T and L, were found. These two types of slow inward current in both heart preparations were nearly similar in their voltage, kinetics, and pharmacology. Apamin, a slow Ca2+ action potential blocker in old embryonic chick heart, was found to block the L-type ICa (IL) in a dose-dependent manner without affecting the T-type ICa in both heart cell preparations. The blockade of the IL by apamin was completely reversible upon washout with apamin-free solution. Therefore, when compared with nifedipine or to PN 200-110, apamin seems to be a highly potent L-type Ca2+ channel blocker in heart cells.
Bkaily
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Department of Physiology and Biophysics, Faculty of Medicine, University of Sherbrooke, Québec, Canada.
Sculptoreanu
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A
Jacques
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D
Economos
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D
Ménard
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D
D000818:Animals; D001030:Apamin / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002478:Cells, Cultured; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005333:Fetus / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008345:Manganese / Q000494:pharmacology; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011802:Quinidine / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D001030:Apamin; D008345:Manganese; D013779:Tetrodotoxin; D011802:Quinidine