Inhibition of the veratridine-induced increase in cytosolic Ca2+ and respiration by Ca2+ antagonists in isolated cardiac myocytes.
1. We studied the effect of verapamil, nitrendipine, 3',4'-dichlorobenzamil (DCB) and Cd2+ on the increase in cytosolic free Ca2+ ([Ca2+]c) and the rate of O2-uptake induced by depolarization of isolated rat cardiac myocytes with veratridine. 2. The degree of inhibition by the several drugs tested on the increase in [Ca2+]c and respiration was dependent on extracellular Ca2+, pH and Na+. 3. Low verapamil and nitrendipine concentrations (2.5 microM) were fully effective in Ca2+ channel blockade, as indicated from experiments with isoproterenol and in a low-Na+ medium. 4. A complete inhibition of veratridine-induced increase in [Ca2+]c and O2-uptake was attained with higher Ca2+ blocker concentrations (25-30 microM), implying that these processes depend to a major extent on some other Ca2+ transport system, probably Na+/Ca2+ exchange.
Moreno-Sánchez
R
R
Departamento de Bioquimica, Instituto Nacional de Cardiología, D.F. México.
Hansford
R G
RG
D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D005260:Female; D006863:Hydrogen-Ion Concentration; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D009568:Nitrendipine / Q000494:pharmacology; D010101:Oxygen Consumption; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D014701:Veratridine / Q000037:antagonists & inhibitors* / Q000494:pharmacology
D002121:Calcium Channel Blockers; D002104:Cadmium; C041470:3',4'-dichlorobenzamil; D014701:Veratridine; D000584:Amiloride; D009568:Nitrendipine; D012964:Sodium; D014700:Verapamil; D007545:Isoproterenol; D002118:Calcium