Binding of the dihydropyridine calcium channel blocker (+)-[3H] isopropyl-4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-5-methoxycarbonyl-2, 6-dimethyl-3-pyridinecarboxylate (PN200-110) to RINm5F membranes and cells: characterization and functional significance.