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 × 10-8M/5 days ] and the activator S Bay K 8644 [ 5 × 10-7M/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.