Redistribution of Cortical Blood Flow during Renal VasodNatation in Dogs

Abstract

We studied the distribution of cortical blood flow during renal vasodilation induced by four maneuvers; reduction of perfusion pressure, intraarterial infusion of acetylcholine, and diuresis induced by ethacrynic acid or mannitol. Dogs were anesthetized with pentobarbital and urinary losses replaced. Bloodflow of the denervated kidney was measured by an electromagnetic flowmeter,and distribution of renal cortical blood flow analyzed by the radioactive microsphere technique. Acetylcholine caused progressively greater proportional vasodilation from superficial to deep cortex. The resulting pattern of flow redistribution was nearly identical to that observed in response to reduced perfusion pressure (autoregulation). Since the same pattern of heterogeneous cortical response was elicited by two qualitatively different stimuli, we propose that it reflects differential responsiveness of individual cortex zones. Ethacrynic acid redistributed flow in a different pattern, augmenting the proportion to the middle, but not the juxtamedullary cortex. High urine flow was excluded as a nonspecific basis for this difference, since acetylcholine produced its usual pattern of redistribution during the ethacrynic acid-induced diuresis. Additionally, ethacrynic acid-induced flow redistribution was not secondary to high urine flow per se, since mannitol diuresis did not significantly alter distribution of flow.