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 Rb-86() efflux rate were evaluated in strips of dog and rat mesenteric arter ies and compared with the variables obtained from ATP-depleted strips of both species. The cromakalim-induced relaxation was competitively a ntagonized by glibenclamide, with similar pA(2) values, in both dog an d rat mesenteric arteries. Glibenclamide caused an enhancement of the precontraction or a reversal of the cromakalim-induced inhibition in t he mesenteric arteries of both species when cromakalim was applied pri or to or during phenylephrine-contraction. The Rb-86(+) efflux rate fr om the mesenteric arteries was significantly increased in both species after application of cromakalim (10 mu M). However, in the ATP-deplet ed mesenteric artery (verified by high performance liquid chromatograp hy), an increase in Rb-86(+) efflux and a glibenclamide-induced enhanc ement of contraction were observed in the rat, but not in the dog. Tak en together, between dog and rat mesenteric arterial strips, a differe ntial effect of ATP depletion with 2-deoxyglucose plus oligomycin was identified in the activation of ATP-sensitive K+ channels, but not of cromakalim.