EFFECT OF DOPAMINE(2) BLOCKADE ON RENAL-FUNCTION UNDER VARIED SODIUM-INTAKE

This study explored the role of the dopamine-2 receptor (DA(2)) in the control of renal blood flow (RBF) and the influence of variations in sodium intake. These relationships have not been previously defined in man. Seven normotensive male subjects underwent a low dose dopamine ( DA) infusion (1 mu g/kg.min) for 3 h, known to activate both DA(1) and DA(2) receptors. The effect of DA(2) receptor on renal hemodynamics w as studied using a relatively specific DA(2) blocker [domperidone (DOM ); 60 mg, orally] alone and with a DA infusion. Systemic and renal hem odynamics parameters were measured noninvasively. Urinary prostacyclin was measured in 3-h urine specimens, obtained during the DA infusion. The DA infusion increased RBF and prosta-cyclin during both normal an d high salt diets, but this effect was attenuated on a low salt diet. DOM alone significantly reduced basal RBF during normal (1304 +/- 48 v s. 1175 +/- 45 ml/min.1.73 m(2); P < 0.01) and low salt diets (1402 /- 80 vs. 1220 +/- 101 mL/min. 1.73 m(2); P < 0.02), but was without eff ect during high sodium intake. DOM had no effect on prostacyclin excre tion at any level of salt intake. These results suggest that both DA(1 ) and DA(2) are activated in renal vessels by DA(1) and that DA(2) rec eptors play a role in the renal vasodilating action of DA. Changes in sodium balance alter the actions of the two receptors (DA(1) and DA(2) ) in a coordinated fashion in the regulation of RBF.