抄録
Follicular cells surrounding Xenopus oocyte under voltage-clamp produce K+ current responses to follicle stimulating hormone (FSH), Adenosine (Ade) and intracellularly applied cAMP, presumably due to the opening of KATP channel. To identify the KATP channel subtype involved in the FSH-and Ade-induced responses, we investigated effects of various K+ channel openers (KCOs) and sulfonylurea receptor (SUR) blockers on the agonist-induced responses. Applications of PCO400, Cro, pinacidil but not diazoxide produced K+ current responses similar to the FSH- and Ade-induced responses in the order of PCO400 < Cro << pinacidil in favor of SUR2A. Application of glibenclamide, phentolamine and tolbutamide suppressed all the K+ current responses to FSH, Ade, cAMP, and KCOs. Furthermore, the both FSH- and Ade-induced responses were markedly augmented during the KCO-induced responses or vice versa. I-V curves for the K+ current responses induced by Cro, Ade and FSH showed outward rectification in normal [K+]o but weak inward rectification in 122 mM [K+]o. In addition, as observed previously with FSH- and Ade-induced responses, stimulations of P2Y receptor by UTP or PKC by PDBu markedly depressed the K+ current response to KCO in favor of Kir6.1. These results suggest that the K+ current responses to FSH and Ade may be produced by opening of a novel type of KATP channel comprising SUR2A and Kir6.1. [J Physiol Sci. 2008;58 Suppl:S77]
