Direct Renal Vasodilatation Produced by Dopamine in the Dog.

• We have recently demonstrated that intravenous administration of the naturally occurring catecholamine, dopamine, increases effective renal plasma flow, glomerular filtration rate, and sodium excretion in normal human subjects. Since renal plasma flow increased in the absence of an alteration in mean arterial pressure, it was concluded that renal vascular resistance was decreased by dopamine. Comparable effects were observed in the dog. The present study was undertaken to characterize these findings more fully. The effects of intravenous dopamine infusion on directly measured renal blood flow and blood pressure were compared with those of isoproterenol and norepinephrine, chosen as catecholamines with strong vasodilator and vasoconstrictor effects, respectively. In addition, renal blood flow responses to direct renal arterial injections of these three agents were studied. To determine whether the renal vascular responses to dopamine were typical of other vascular beds, comparable experiments studying femoral blood flow responses to intraarterial injections of dopamine, isoproterenol,