Potentiation of recombinant L-type Ca channel currents by alpha(1)-adrenoceptors coexpressed in baby hamster kidney (BHK) cells

Ln cardiac myocytes, the effect of alpha(1)-adrenergic stimulation on L-typ e Ca current remains to be clarified. We examined this issue by the transie nt coexpression of alpha(1)-adrenoceptors on BHKC12 cells, where recombinan t Ca channels composed of cardiac al subunit and skeletal beta, gamma, alph a(2)/delta subunits were stably expressed. After transfection of plasmid DN A encoding bovine alpha(1C)-adrenoceptors, bath-applied phenylephrine poten tiated the cloned Ca channel current during perforated-patch whole-cell rec ording by 26+/-6% in 6 out of 12 cells. The potentiation was elicited also by methoxamine, and was blocked by prazosin. Phenylephrine also increased t he channel open probability during cell-attached single channel recording i n 7 out of 15 cells. The ratio of successful modulation of Ca channels was in accordance with the ratio of successful expression of alpha(1)-adrenocep tors, as estimated by beta-galactosidase staining. These results suggest th at the stimulation of alpha(1C)-adrenoceptors is linked to potentiation of cardiac L-type Ca current. BHK cells provide a valuable expression system t o study the modulation of Ca channels evoked by a receptor stimulation.