ROLE OF NA+ K+ ATPASE ON THE RELAXATION OF RABBIT EAR AND FEMORAL ARTERIES/

The role of Na+/K+ ATPase in vascular relaxation has been studied by d etermining its inhibitory effects on 2-mm segments from rabbit central ear and femoral arteries, mounted for isometric tension recording. Ac etylcholine (10(-8)-10(-4) M), the nitric oxide donor sodium nitroprus side (10(-8)-3 x 10(-4) M), the potassium channel agonist cromakalim ( 10(-8)-3 x 10(-5) M), histamine (10(-8)-10(-4) M) in the presence of t he H-1 antagonist chlorpheniramine (10(-5) M), and papaverine (10(-6)- 3 x 10(-4) M) all produced arterial relaxation in ear and femoral arte ries precontracted with endothelin 1. Addition of potassium (6 x 10(-3 ) 1 . 2 x 10(-2) M) caused relaxation of the same arteries preincubate d in potassium-free medium. Ouabain (10(-5) M) an inhibitor of Na+/KATPase, reduced the relaxation of ear arteries, but not of femoral art eries, in response to acetylcholine; it also reduced the response to s odium nitroprusside, cromakalim or histamine, and abolished the relaxa tion to potassium, but did not modify the response to papaverine, in b oth types of artery. These results suggest that Na+/K+ ATPase might pl ay a role in the relaxation of ear and femoral arteries to nitrovasodi lators, to potassium channel openers and to activation of histamine re ceptors, and that Na+/K+ ATPase might play a role in the cholinergic r elaxation of ear, but not femoral arteries, suggesting that the mechan ism of cholinergic relaxation might differ in each type of artery.