Inhibition of the veratridine-induced increase in cytosolic Ca2+ and respiration by Ca2+ antagonists in isolated cardiac myocytes. |
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Authors: | R Moreno-Sánchez R G Hansford |
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Institution: | Departamento de Bioquimica, Instituto Nacional de Cardiología, D.F. México. |
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Abstract: | 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. |
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