Effects of cromakalim, RP49356, diazoxide, glibenclamide and galanin in rat portal vein.

The study investigated the possible involvement of an ATP-sensitive potassium (K) channel in the relaxant actions of K channel openers in rat portal vein. The effects of glibenclamide on the relaxant responses and rises in 86Rb efflux evoked by cromakalim, RP49356 and diazoxide were studied. The effects of galanin and depletion of intracellular ATP concentrations [( ATP]i) were also examined. Galanin increased mechanical activity and 86Rb efflux, effects most likely mediated via galanin receptors rather than a direct action on a K channel. Glibenclamide inhibited the relaxant responses and rises in 86Rb efflux evoked by cromakalim, RP49356 and diazoxide. Reduction of [ATP]i caused relaxation and this effect was partially reversed by glibenclamide. The restored activity was abolished by cromakalim. These results suggest that an ATP-sensitive K channel is present on rat portal vein and that it may be involved in the relaxant actions of cromakalim, RP49356 and diazoxide.