AJP - Heart and Circulatory Physiology, Vol 243, Issue 5 779-H787, Copyright © 1982 by American Physiological Society
Fluid volumes and pressor responsiveness in two-kidney rabbits with renal artery stenosis
J. A. Johnson, K. D. Kurz, S. Siripaisarnpipat, D. W. Zeigler and C. G. Payne
This study examined body fluid volumes, the pressor responses to
norepinephrine (NE), and the cardiovascular responses to NE before and
during infusion of an angiotensin II (ANG II) antagonist in two-kidney
rabbits with unilateral renal artery stenosis (RAS) of 3 and 30 day
duration. Three separate experiments were performed. In the first
experiment, plasma volume, extracellular fluid volume, and total body water
were measured by the distribution volumes of radioiodinated serum albumin,
35SO4, and tritiated water, respectively. No differences were seen for any
of these volumes between the 3- or 30-day RAS rabbits and their controls.
In the second experiment, pressor responses to infusions of several doses
of NE were examined; rabbits with 3- and 30-day RAS had exaggerated pressor
responses to all doses of NE when compared with the control rabbits. In the
third experiment, infusion of NE at 800 ng.min-1.kg body wt-1 resulted in
more pronounced increases in mean arterial pressure and total peripheral
resistance (TPR) in the 3- and 30-day RAS rabbits than in the controls;
after infusion of [Sar1-Ile8] ANG II the increases in mean arterial
pressure and TPR during NE infusion were blunted and were of the same
magnitude as in the control group. In all experiments the 30-day RAS
rabbits were hypertensive, whereas the 3-day RAS rabbits were normotensive;
also, plasma renin activity (PRA) values were normal in both the 3- and
30-day RAS groups. These studies demonstrated that increases in body fluid
volumes are not necessary for pressor and vascular hyperresponsiveness
probably is mediated by ANG II, despite normal PRA values.
