Three correlations between extracellular calcium concentration and myocardial cell injury induced by drugs.

Primary cultures of newborn rat myocardial cells were treated in various extracellular calcium concentrations (0, 1.35, 2.7, 4.05, and 5.4 mM) with three different drugs; namely, ouabain, sulmazole, and chlorpromazine. Lactate dehydrogenase (LDH) release was used as an indicator of damage. The results showed 10(-3) M ouabain caused apparent damage of the cells and the damage was increased by an increased extracellular calcium concentration. Sulmazole (10(-3)M) caused damage of the cells in the absence of calcium; but it did not cause damage of the cells in the presence of calcium; it protected the cells from damage caused by high calcium concentrations (4.05 and 5.4 mM). Chlorpromazine (1.6 X 10(-4)M) caused severe damage of the cells. The various calcium concentrations had no influence on the degree of the damage. Correlation coefficients showed that correlations between the calcium concentrations and the cell damage caused by ouabain, sulmazole and chlorpromazine were positive correlation, negative correlation, and no correlation, respectively. It is suggested that influx of extracellular calcium is not a final common pathway of drug-induced myocardial cell injury, although it plays an important role in cell injury.