Modification by cGMP of glibenclamide-sensitive K+ currents in Xenopus oocytes

Effects of sodium nitroprusside, 8-bromo cGMP and methylene blue on the glibenclamide-sensitive K+ current evoked by K+ channel openers in Xenopus oocytes were studied. Sodium nitroprusside (0.1-1 mM, an activator of guanylate cyclase) enhanced by 20-50% the K+ currents induced by KRN2391, nicorandil and cromakalim (K+ channel openers). 8-Bromo cGMP (1 mM) also increased the K+ current by 40-60%. Methylene blue (10 microM, an inhibitor of guanylate cyclase) irreversibly blocked the K+ current by about 20-30%. These results suggest that the activation of glibenclamide-sensitive K+ channels by K+ channel openers is modulated either positively or negatively by intracellular cGMP in oocytes.