Inhibition of cromakalim-activated K⁺ current by ethanol in follicle-enclosed Xenopus oocytes

Abstract.

Ethanol has been reported to modulate arterial dilation and insulin secretion. ATP-inhibited K⁺ channels (K_ATP) are reported to have regulatory roles during these events. In the present study, the effect of ethanol on K⁺ currents activated by the K_ATP channel opener cromakalim was investigated in follicular cells of Xenopus oocytes. The results indicate that ethanol in the concentration range of 10–300 mM (approximately 0.06%–2% v/v) reversibly inhibits the cromakalim-induced K⁺ currents. The 50% of maximal ethanol effect was obtained at 53 mM. Inhibition of cromakalim-activated K⁺ current by ethanol was non-competitive. In oocytes treated with the Ca²⁺-chelator BAPTA, inhibition of cromakalim-induced K⁺ currents by ethanol was not altered, suggesting that Ca²⁺-activated second messenger pathways were not involved in the actions of ethanol. Similarly, currents activated by 8-Br-cAMP were also inhibited by ethanol, but the ethanol inhibition of 8-Br-cAMP-activated currents was significantly less than inhibition of cromakalim-activated currents by ethanol. These results indicate that cromakalim-activated K⁺ currents in follicular cells of Xenopus oocytes were modulated by ethanol.