AJP - Heart and Circulatory Physiology, Vol 257, Issue 2 502-H505, Copyright © 1989 by American Physiological Society
Mechanism mediating hypotensive effect of ANF in sodium-depleted dogs
J. P. Granger, E. Meadows, S. Sooudi and D. L. Stacy
Department of Physiology, Eastern Virginia Medical School, Norfolk 23501.
Previous studies have indicated that suppression of renin release and
antagonism of the vasoconstrictor actions of angiotensin II (ANG II) may be
important mechanisms whereby atrial natriuretic factor (ANF) decreases
arterial pressure (AP). The objective of this study was to determine the
importance of renin suppression and ANG II antagonism in mediating the
hypotensive effects of ANF in Na-depleted, high-renin dogs. Infusion of ANF
(300 ng.kg-1.min-1) for 45 min in Na-depleted dogs decreased plasma renin
activity (PRA) from 7.5 +/- 2.3 to 3.1 +/- 1.1 ng ANG I.ml-1.h-1.
Associated with this fall in PRA was a significant reduction in AP and
total peripheral resistance (TPR). Although cardiac output (CO) tended to
fall, statistically significant reductions in CO (2.11 +/- 0.19 vs. 1.99
+/- 0.10 l/min) did not occur. In contrast to these findings, infusion of
ANF (300 ng.kg-1.min-1) in Na-depleted dogs with fixed circulating levels
of ANG II had no significant effect on AP or TPR. Results from this study
suggest that renin suppression may be an important mechanism whereby ANF
reduces AP in Na-depleted dogs. The results also suggest that antagonism of
the vasoconstrictor actions of ANG II is not a potent mechanism whereby ANF
decreases AP.
