Mechanism of inhibition of renin secretion by increased left atrial pressure.

Experiments were designed to elucidate the mechanism of the failure of systemic hypotension to stimulate renin release in the presence of elevated left heart pressure. We conducted a series of graded ascending aortic and suprarenal cuff inflations in dogs with bilateral renal denervation (n = 5). The renal perfusion pressure (RPP) was reduced by 10, 20, and 30% of control by inflation of either cuff. Comparison of the renin response with inflation of the ascending aortic to the suprarenal cuff revealed a clear increase in the threshold required to elicit a renin response to graded reduction of RPP after inflation of the ascending aortic cuff. These results may be explained by differential effects of the two maneuvers on left heart pressure. Left atrial pressure increased during inflation of the ascending aortic cuff but did not change during inflation of the suprarenal cuff. Since the kidneys were denervated, the shift in threshold must be caused by a humoral substance(s). In conclusion, our findings suggest that the efferent pathway of potent inhibition of renin release from the left heart is mediated, at least partially, by a humoral substance.