Characteristics of pressure-flow regulation by the kidney

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Abstract
Pressure-flow relationships in the dog kidney were studied by means of a square wave, noncannulating electromagnetic flowmeter probe placed around the renal artery by way of a retroperitoneal approach. Renal artery pressure was varied by a clamp on the artery and recorded via a needle inserted distal to the probe and clamp. Reductions in artery pressure from control levels demonstrated complete regulation of flow from control level down to 70 mm Hg, incomplete regulation from 50–70 mm Hg, and inability to compensate further below 50 mm Hg. Insignificant regulation was found in the iliac vascular bed by this technique. Recovery time of flow occurred within 5–60 sec following occlusion and was more prolonged at lower levels of artery pressure. The findings of a sharp inflection in the pressure-flow plot at approximately 70 mm Hg and a time course of regulation and recovery pattern varying with the reduced artery pressure suggest an active mechanism controlled by a sensitive feedback system. Submitted on September 18, 1961