Inhibitory action of calcium antagonists on ATP-dependent calcium uptake by the renal cortical microsomes.

Effects of Ca2+ antagonists, verapamil and diltiazem, on uptake and release of Ca2+ by microsomes of the renal cortex were studied. Verapamil inhibited the ATP-dependent Ca2+ uptake by renal microsomes. Addition of 0.8 mM verapamil was required to produce 50% inhibition of the ATP-dependent CA2+ uptake. Diltiazem also depressed the Ca2+ uptake was not due to an increased permeability for Ca2+, since release of Ca2+ from the microsomes was not significantly affected by either drug. It is proposed that verapamil and diltiazem inhibit Ca2+ transport by interfering with an active process of Ca2+ accumulation in microsomes of the renal cortex.