Control of expression of the 1,4-dihydropyridine receptor in BC3H1 cells

To determine whether expression of the 1,4-dihydropyridine receptor of skeletal muscle Ca2+ channels is regulated by signals that impinge on muscle-specific gene expression, BC3H1 muscle cells were analyzed using (+)[3H]PN200-110 as a probe for the receptor. No dihydropyridine binding sites were detected in proliferating cells. Binding site density increased following serum withdrawal, peaking at day six, with little or no change in Kd (approximately equal to 250 pM, similar to that seen in skeletal muscle). No DHP binding sites were detected in BC3H1 cells bearing an activated c-H-ras oncogene. Induction of the dihydropyridine receptor was reversibly blocked by 200 pM transforming growth factor beta. The results indicate that formation of dihydropyridine-sensitive Ca2+ channels may require up-regulation of the dihydropyridine receptor itself, and that transforming growth factor beta is a potent, reversible inhibitor of this receptor in BC3H1 muscle cells.