Homologous regulation of voltage-dependent calcium channels by 1,4-dihydropyridines

Chronic treatment of PC 12 cells with the 1,4-dihydropyridine Ca2+ channel antagonist nifedipine [5 x 10-8M/5 days] and the activator S Bay K 8644 [5 x 10-7 M/5 days] resulted in up- and down-regulation of 1,4-dihydropyridine binding site density by 29 and 24%, respectively, without change in affinity. These changes in binding site density represent functional changes as indicated by the corresponding changes in K+ depolarization-induced 45Ca2+ uptake and in whole cell currents carried by Ba2+ ions. This homologous regulation of voltage-dependent Ca2+ channels [VDCC] by potent and specific ligands parallels that observed for other classes of membrane receptors.