Redistribution of Renal Intracortical Blood Flow during Dopamine Infusion in Dogs

We determined the effect of intravenous and renal intra-arterial infusion of dopamine on the distribution of intracortical blood flow in kidneys of anesthetized dogs. Total renal and renal intracortical blood flows in dogs receiving dopamine intravenously were quantified by the radioactive microsphere technique with reference sampling. In dogs receiving dopamine by renal intra-arterial infusion, total renal and renal intracortical blood flows were determined from radioactive microsphere and electromagnetic flowmeter data. Tissue perfusion rates for the total kidney, the renal cortex, the renal outer cortex, and the renal inner cortex increased following either intravenous or direct renal intra-arterial infusion of dopamine. Dopamine infusion by either method caused a relative redistribution of renal blood flow from the outer twothirds to the inner one-third of the renal cortex. During direct dopamine infusion into the renal artery, no significant changes in renal hemodynamics occurred in the contralateral kidney. No changes in arterial blood pressure occurred during dopamine infusion by either method. These observations imply that the change in the fractional distribution of renal intracortical blood flow following dopamine infusion is not dependent on a systemic mode of action. This pattern of flow redistribution suggests that the intrarenal dopamine-specific receptor may be in higher number in the inner cortex or that the redistribution of cortical flow after dopamine infusion may reflect differing initial physiological states of the inner and outer cortical receptors for dopamine.