RECEPTOR-MEDIATED MODULATION OF RAT K-V1.2 IN XENOPUS-OOCYTES

To investigate mechanisms for the receptor-mediated inhibition of a rat cardiac K+ channel clone (K-V1.2), we coexpressed K-V1.2 with a subtype of endothelin receptors (ET(A)) in Xerzopus oocytes. Effects of endothelin ET(A) receptor stimulation were mimicked by application of PMA (4-beta-phorbol 12-myristate 13-acetate; 0.1 mu M) or intracellular injection of CaCl2 (estimated concentration of 1 mu M). These effects diminished in the presence of staurosporine (1 mu M) or EGTA (estimated concentration of 5 mM). These results suggest that both activation of protein kinase C and an increase in intracellular Ca2+ contribute to the suppression.