Calcium channel antagonist effects of spironolactone, an aldosterone antagonist

The effect of spironolactone on the contractility of vascular smooth muscle cells and on calcium channel currents of isolated cells was investigated using the patch-clamp method. Concentrations of 10 and 60 microM of spironolactone resulted in 50 and 100% inhibition, respectively, of isometric contractions. Whereas fast calcium channel current was essentially unaffected by spironolactone, slow calcium channel current was inhibited 50% by 5 to 7 microM concentrations of the drug. These results suggest that spironolactone acts on slow calcium channels in a manner similar to that of calcium blockers.