Relaxant effects of cromakalim and ATP depletion in dog and rat mesenteric arteries--species differences.

In the present study, the effects of cromakalim on tension and 86Rb+ efflux rate were evaluated in strips of dog and rat mesenteric arteries and compared with the variables obtained from ATP-depleted strips of both species. The cromakalim-induced relaxation was competitively antagonized by glibenclamide, with similar pA2 values, in both dog and rat mesenteric arteries. Glibenclamide caused an enhancement of the precontraction or a reversal of the cromakalim-induced inhibition in the mesenteric arteries of both species when cromakalim was applied prior to or during phenylephrine-contraction. The 86Rb+ efflux rate from the mesenteric arteries was significantly increased in both species after application of cromakalin (10 microM). However, in the ATP-depleted mesenteric artery (verified by high performance liquid chromatography), an increase in 86Rb+ efflux and a glibenclamide-induced enhancement of contraction were observed in the rat, but not in the dog. Taken together, between dog and rat mesenteric arterial strips, a differential effect of ATP depletion with 2-deoxyglucose plus oligomycin was identified in the activation of ATP-sensitive K+ channels, but not of cromakalim.