Association between Autoregulation and Pressure Dependency of Renal Vascular Responsiveness in Dogs

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Abstract
We studied the influence of perfusion pressure (arterial pressure minus venous pressure) on the magnitude of responses of renal blood flow to intraarterial injections of acetylcholine, norepinephrine, adenosine, and angiotensin. The left kidney of dogs anesthetized with pentobarbital was denervated, renal arterial flow measured with an electromagnetic flowmeter, and renal perfusion pressure varied by constricting the aorta or renal vein. The percent changes in renal blood flow produced by standardized doses of each vasoactive agent were considered an indication of vascular responsiveness. In kidneys having autoregulation, vascular responsiveness so defined was a function of renal perfusion pressure. In contrast, this correlation was not characteristic of denervated, non-autoregulating canine hindlegs. These experiments do not distinguish between the alternate possibilities that changes in renal vascular responsiveness may have a role in autoregulation or may be a consequence of it.