Arteriolar responses to norepinephrine and ouabain in early 1-kidney, 1-clip hypertension in rats.
We assessed the role of putative circulating ouabainlike factors on in vivo arteriolar function in rats with very early (less than or equal to 7 days, mean 3 days), benign, one-kidney, one-clip (1K1C) hypertension. Thus we measured vascular responses in vasodilated (nitroprusside or adenosine), vascularly isolated, innervated hindlimb vascular beds of chloralose-anesthetized 1K1C rats perfused with their own blood at 1 ml/min. Complete dose-response curves to norepinephrine in 19 1K1C compared with 25 uninephrectomized (1K) normotensive control rats showed unchanged thresholds and 50% effective dosages. Magnitude of ouabain-induced leftward shifts of the dose-response curve in 29 1K1C and 30 1K rats were similar. In 1K1C, compared with 1K, limb resting resistance was elevated by 45% (P less than 0.001), and limb resistance at maximal vasodilation was elevated by 15% (P less than 0.02). These results provide no evidence in this form and stage of hypertension that humoral ouabainlike inhibitors of the sodium-potassium pump evoke physiologically significant inotropic effects in arterioles in vivo. However, the results suggest that significant increases in arteriolar wall-to-lumen ratio occur in the earliest stages (3 days) of hypertension and probably contribute to the elevated resistance.
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D000818:Animals; D004305:Dose-Response Relationship, Drug; D006614:Hindlimb / Q000098:blood supply; D006978:Hypertension, Renovascular / Q000503:physiopathology*; D007473:Ion Channels / Q000502:physiology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology*; D010042:Ouabain / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects*
D007473:Ion Channels; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D009638:Norepinephrine