Binding of the calcium channel blocker nitrendipine to its receptor in purified sarcolemma from canine cardiac ventricle

High affinity binding of the 1,4-dihydropyridine calcium channel blocker [³H]nitrendipine was found in cardiac sarcolemma but not cardiac sarcoplasmic reticulum or mitochondria. Sarcolemmal binding of [³H]nitrendipine was saturable and reversible, with a maximum (B_max) of approximately 1 pmol/mg protein and a K_d of approximately 0.14 nm. Displacement of sarcolemma-bound [³H]nitrendipine by other nifedipine analogs was stereospecific. The K_d for nitrendipine binding was approximately three orders of magnitude lower than the IC₅₀ for the negative inotropic effect of this drug on isolated cat myocardium.