Effect of verapamil on the calcium and magnesium transports of rat kidney cortex mitochondria.

The effect of verapamil on Ca2+ and Mg2+ accumulation was investigated in isolated rat kidney cortex mitochondria. For the 50% inhibition of Ca2+ accumulation, 2 x 10(-4) M verapamil concentration was required in the presence of ATP (2 mM) and phosphate (5 mM). Omission of phosphate from the medium increased the inhibitory effect of verapamil on Ca2+ accumulation. Verapamil had no effect on Ca2+ accumulation in the presence of both ATP and succinate (7.8 mM), but further addition of phosphate resulted in a significant inhibition of Ca2+ accumulation by verapamil. Mg2+ accumulation of mitochondria was similarly depressed by verapamil. The same tendency was found as for the modification of verapamil effect by acetate in mitochondrial Ca2+ and Mg2+ accumulation. Succinate oxidation of mitochondria was not affected by verapamil in the absence of phosphate, but was inhibited by verapamil in the presence of phosphate. Therefore, it seemed reasonable to assume that the depression of Ca2+ and Mg2+ transport of mitochondria by verapamil is modulated by permeant anions.