DOPAMINERGIC MEDIATION OF THE NATRIURETIC RESPONSE TO VOLUME EXPANSION

  • 1 January 1985
    • journal article
    • research article
    • Vol. 105  (2) , 214-218
Abstract
Previous studies have shown a direct relationship between urinary Na excretion and both urinary dopamine excretion and plasma dopamine levels. The significance of this relationship is unclear. The effect of dopaminergic blockade on the renal response to volume expansion produced by the infusion of 2 l 0.9% saline solution i.v. over 4 h in a group of 6 healthy adult volunteers previously shown to have appropriate Na balance was studied. The dopamine receptor antagonist metoclopramide was administered i.v. at a dose of 10 mg/h throughout the study period; a separate group of control subjects received saline infusion without metoclopramide. During saline infusion urinary Na excretion increased steadily in controls, from a basal level of 127 .+-. 25 .mu.Eq/min to a peak value of 451 .+-. 83 .mu.Eq/min (P < 0.005) during the 4th h of infusion. The study group receiving saline solution along with metoclopramide failed to show any significant increase in urinary Na excretion over the basal levels. Cumulative Na excretion during saline loading was significantly less in those receiving saline solution with metoclopramide (55 .+-. 14 mEq) than in controls (101 .+-. 15 mEq) (P < 0.05). The plasma aldosterone levels in the control group receiving saline solution alone fell steadily from a preinfusion level of 11.0 .+-. 0.9 ng/dl to the nadir of 6.5 .+-. 0.9 ng/dl (P < 0.02), reached during the 3rd h of infusion. In the study group receiving saline solution with metoclopramide, the plasma aldosterone levels remained unchanged. Apparently, metoclopramide attenuates the natriuretic response to volume expansion produced by saline infusion and prevents the suppression of plasma aldosterone levels produced by saline infusion. Dopamine may play a critical role in mediating both the natriuretic response and the plasma aldosterone response to acute volume expansion.