Elevated cardiac pressure inhibits renin release after arterial hypotension in conscious dogs

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Abstract
The relative roles of cardiopulmonary, sinoaortic and renal baroreceptors in the regulation of plasma renin activity (PRA) were evaluated in dogs with chronically implanted cuffs around the ascending aorta proximal to the brachiocephalic artery, the abdominal aorta just proximal to both renal arteries, or both. Inflation of either cuff was adjusted to cause a reduction of distal arterial pressure and hence renal perfusion pressure (RPP) of 0, 5, 10, 20, or 30% of control for 1 h. Reduction of RPP by inflation of the suprarenal cuff (n = 4) led to a significant (P < 0.05) increase in PRA throughout the dose range examined. However, constriction of the ascending aorta (n = 7) to cause identical reductions in RPP failed to increase PRA. The apparent paradox in these results may be explained by differential effects of the 2 maneuvers on left atrial pressure. Left atrial pressure increased dose dependently during inflation of the ascending aortic cuff but did not change during inflation of the suprarenal cuff. To determine if elevated right atrial pressure (RAP) would inhibit renin release after systemic hypotension, another group of dogs (n = 4) was prepared with cuffs around the pulmonary artery. Inflation of the pulmonary cuff to cause similar systemic hypotension led to significant (P < 0.05) increases in PRA and RAP. Powerful inhibitory signals, arising from the left heart, evidently can inhibit renin release in response to systemic hypotension.

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