Potentiation of recombinant L-type Ca channel currents by alpha1-adrenoceptors coexpressed in baby hamster kidney (BHK) cells.
In cardiac myocytes, the effect of alpha1-adrenergic stimulation on L-type Ca current remains to be clarified. We examined this issue by the transient coexpression of alpha1-adrenoceptors on BHKC12 cells, where recombinant Ca channels composed of cardiac alpha1 subunit and skeletal beta, gamma, alpha2/delta subunits were stably expressed. After transfection of plasmid DNA encoding bovine alpha1C-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 alpha1-adrenoceptors, as estimated by beta-galactosidase staining. These results suggest that the stimulation of alpha1C-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.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type; D002417:Cattle; D002478:Cells, Cultured; D006224:Cricetinae; D015640:Ion Channel Gating / Q000187:drug effects; D007668:Kidney / Q000378:metabolism; D008729:Methoxamine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011869:Radioligand Assay; D018340:Receptors, Adrenergic, alpha-1 / Q000096:biosynthesis / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects