Abstract

The effects of arterial injections of dopamine on femoral and renal blood flow were compared with those of isoproterenol, norepinephrine and bradykinin after POB pretreatment. Dopamine was found to have a vasodilator action on the hind limb, which was antagonized by pronethalol and DCI. The potency of dopamine as a femoral vasodilating agent was very low compared to that of isoproterenol. In contrast, dopamine caused renal vasodilation by a qualitatively different mechanism, as indicated by a higher relative potency within the series of adrenergic agonists and the lack of antagonism by selective beta adrenergic blockade. This property cannot be attributed to conversion of dopamine to tetrahydropapaveroline which causes renal vasodilation by a beta adrenergic mechanism. Also, the metabolism of dopamine to norepinephrine,3,4-dihydroxyphenylacetic acid or 3-methoxy-4-hydroxyphenylethylamine is not the basis for this property. Furthermore, the renal vasodilation was not antagonized by atropine or eliminated by reserpine pretreatment. The ability of dopamine to dilate the renal vascular bed without producing a qualitatively similar direct effect on the femoral vascular bed sets it apart from agents such as papaverine and the nitrites. The physiologic significance of the renal vascular effects of dopamine remains to be determined.