AJP - Heart and Circulatory Physiology, Vol 242, Issue 1 107-H112, Copyright © 1982 by American Physiological Society
Acute inhibition of renin release during left circumflex coronary occlusion in dogs
A. Livnat and J. E. Zehr
We examined the reflex effect of brief left circumflex coronary artery
occlusion (CAO) on renal blood flow (RBF) and renin secretion (RS). Studies
were conducted in alpha-chloralose-anesthetized dogs maintained on a
salt-free diet for at least 3 days. A snare was placed around the left
circumflex artery near its origin. The left renal artery and vein were
exposed via flank incision, a flow probe was placed around the artery, and
a curved needle was inserted into the vein for collection of renal venous
blood. Values of blood pressure (BP), RBF, and RS were obtained for a
30-min control period, 4 min after the completion of a 10-ml/kg hemorrhage,
1 and 5 min after CAO, and 15 min after reinfusion. The CAO consisted of
two 1-min occlusions separated by a 1-min interval. The results indicate
that CAO reflexively inhibits the RS response to nonhypotensive hemorrhage
and prevents renal vasoconstriction (P less than 0.05, n = 7). Both effects
were completely abolished after vagotomy (n = 5). Renal denervation also
abolished the response (n = 5). No response was observed during identical
time controls (n = 5). The response was more pronounced in dogs with
carotid sinus denervation, even though CAO resulted in marked reductions in
BP (20%) under these conditions. These results demonstrate the presence of
a cardiorenal reflex that can be activated by myocardial hypoxia and that
acutely suppresses RS. This response is more pronounced in the absence of
carotid sinus buffering.
