Acute inhibition of renin release during left circumflex coronary occlusion in dogs

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.