AJP - Heart and Circulatory Physiology, Vol 233, Issue 2 191-H195, Copyright © 1977 by American Physiological Society
Renin release and pressor response to renal arterial hypotension: effect of dietary sodium
J. C. Fray, M. D. Johnson and A. C. Barger
Changes in plasma renin activity (PRA) and mean arterial pressure (MAP)
produced by renal arterial hypotension were studied in conscious,
adrenalectomized dogs maintained on low-, normal-, or high-Na diet during
constant steroid replacement therapy. In animals maintained on a low-Na
diet, reduction of renal perfusion pressure to 50 mmHg for 45 min increased
MAP 40 +/- 3 (SE) mmHg, while PRA rose rapidly by 36.5 +/- 6 ng ml-1 h-1.
Similar renal hypotension in dogs maintained on a normal-Na diet increased
MAP only 21 +/- 3 mmHg while PRA rose 5.5 +/- 0.9 ng ml-1 h-1; dogs on
high-Na intake had a 6 +/- 1 mmHg pressure rise without a significant
change in PRA. The rise in MAP correlated well with the log deltaPRA.
Calculated open-loop gain was -1.2, -0.7, and -0.1 in dogs on low-,
normal-, and high-Na diets, respectively. Nonpeptide angiotensin I
converting enzyme inhibitor (CEI) reversed the elevated MAP observed during
reduction of renal perfusion pressure in dogs on low- and normal-Na diets,
but had little effect in dogs on high-Na intake. These observations suggest
that the renin-angiotensin system becomes quantitatively more important in
the regulation of blood pressure as Na intake is reduced.
