Receptor-mediated modulation of rat KV1.2 in Xenopus oocytes

To investigate mechanisms for the receptor-mediated inhibition of a rat cardiac K+ channel clone (KV1.2), we coexpressed KV1.2 with a subtype of endothelin receptors (ETA) in Xenopus oocytes. Effects of endothelin ETA receptor stimulation were mimicked by application of PMA (4-beta-phorbol 12-myristate 13-acetate; 0.1 μM) or intracellular injection of CaCl2 (estimated concentration of 1 μM). These effects diminished in the presence of staurosporine (1 μM) 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.