Effect of insulin on the K⁺ current response induced by adenosine in the follicular cells of Xenopus oocyte

Abstract

Application of adenosine (Ade) induces K⁺-current response in the follicular cells surrounding a Xenopus oocyte under voltage clamp. This Ade-induced K⁺ current response is produced by activation of Gs, subsequent adenylate cyclase, cAMP-dependent protein kinase, and by opening of the ATP-sensitive K channels. Application of 20 nM insulin initially augmented the Ade-induced response, and subsequently depressed. The depressing effect of insulin on the K⁺ current response was irreversible during the washout for more than 3 hours with normal perfusuate. Prior application of 30 nM Lavendustin A (Lav.A), an inhibitor of protein tyrosine kinase, markedly blocked the depressing effect of insulin on the Ade-induced response. These results suggested that the depressing effect of insulin on the Ade-induced K⁺ current response might be regulated by activation of protein tyrosine kinase through the stimulation of insulin receptor. [Jpn J Physiol 54 Suppl:S133 (2004)]