Calcium channel antagonists of the dihydropyridine class have been widely used in the treatment of cardiovascular diseases such as hypertension and angina because of their ability to relax blood vessels and inhibit cardiac contractions (Fleckenstein, 1977). These effects are achieved principally by inhibiting entry of calcium into cells through blockade of voltage-dependent L channels (Hoffman, Nastainczyk, Rohrsten, Schneider, & Sieber, 1987). Because calcium channel antagonists are powerful vasodilators, they have also ...