Influences of changes in calcium concentration and verapamil on the cardiac depressant effect of ethanol in cat papillary muscle.
1. In isolated cat heart papillary muscle electrically driven at a constant rate the depressant effects of increasing concentrations of ethanol on peak tension developed (PTD) was studied in Ringer-Locke solution with different calcium concentrations and with the addition of verapamil. 2. Ethanol induced a concentration dependent decrease in PTD that was significantly greater for each concentration of ethanol in hypocalcic medium (1.1 mM) than in normocalcic medium (2.2 mM). 3. In normocalcic (2.2 mM) medium, verapamil (5.1 x 10(-4) mM) plus ethanol (48.6 and 97.2 mM) produced a decrease in PTD to values significantly greater than those obtained by the addition of ethanol and verapamil alone. Therefore a potentiation of the effects of ethanol by verapamil was observed when both drugs act simultaneously. 4. In hypercalcic medium (4.4 mM), verapamil plus ethanol (48.6 and 97.2 mM) produced a slight decrease in PTD that was significantly less than that observed in normocalcic and hypocalcic mediums. 5. In hypocalcic medium (1.1 mM) verapamil plus ethanol (48.6 and 97.2 mM) produced a decrease in PTD that was of the same relative magnitude (%) as that observed in normocalcic medium. However no potentiation of the combined effects of verapamil plus ethanol was observed in hypocalcic medium.
Martinez
J L
JL
Department of Pharmacology, Faculty of Medicine, University of Chile, Santiago.
Penna
M
M
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002415:Cats; D000431:Ethanol / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology*
D000889:Anti-Arrhythmia Agents; D000431:Ethanol; D014700:Verapamil; D002118:Calcium