Abstract
In cardiac myocytes, the effect of α 1-adrenergic stimulation on L-type Ca current remains to be clarified. We examined this issue by the transient coexpression of α 1-adrenoceptors on BHKC12 cells, where recombinant Ca channels composed of cardiac α 1 subunit and skeletal β, γ, α 2 δ subunits were stably expressed. After transfection of plasmid DNA encoding bovine α 1 C -adrenoceptors, bath-applied phenylephrine potentiated the cloned Ca channel current during perforated-patch whole-cell recording by 26 ± 6 % in 6 out of 12 cells. The potentiation was elicited also by methoxamine, and was blocked by prazosin. Phenylephrine also increased the channel open probability during cell-attached single channel recording in 7 out of 15 cells. The ratio of successful modulation of Ca channels was in accordance with the ratio of successful expression of α 1-adrenoceptors, as estimated by β-galactosidase staining. These results suggest that the stimulation of α 1 C -adrenoceptors is linked to potentiation of cardiac L-type Ca current. BHK cells provide a valuable expression system to study the modulation of Ca channels evoked by a receptor stimulation.
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