The effects of dopamine blockade on the renal response to volume expansion in the primate

It has been reported that dopamine antagonists block the natriuretic but not the diuretic response to volume expansion in man. In order to examine this, anesthetized monkeys (pentobarbital) were volume expanded with isotonic dextran (20% of estimated blood volume) either with (n = 7) or without (n = 8) dopamine blockade (metoclopramide HCl 5 mg followed by an infusion of 10 mg/hr). Similar experiments were done in conscious chair restrained monkeys (5 control, 5 block). In the anesthetized monkey, dopamine blockade did not block the diuretic and natriuretic response to blood volume expansion. No significant changes were observed in any other renal or cardiovascular variables. In four of six experiments in the conscious monkey, the dopamine antagonist blocked the natriuretic response to volume expansion and reduced the diuretic response. In the other two experiments, the antagonist was without effect on the response. It is concluded that a dopaminergic system is involved in the control of blood volume and that this system is inhibited by pentobarbital anesthetic. Supported by NIH grants #HL-13427, #HL-27371 and #HL-32480 and a Nebr. Heart Grant-in-Aid.