AJP - Heart and Circulatory Physiology, Vol 249, Issue 4 851-H858, Copyright © 1985 by American Physiological Society
Arteriolar responses to norepinephrine and ouabain in early 1-kidney, 1-clip hypertension in rats
H. W. Overbeck
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.
