1592 FUNCTION OF RENAL DOPAMINE-2 RECEPTORS

Abstract

We have previously reported presence of dopamine-2 receptors (D2R) in canine intrarenal arteries (IRA) using radioligand binding. To determine the consequences of D2R occupancy we measured the effect of intrarenal infusion of the D2 agonist LY171555 (LY) (10−9 to 10−6M) on renal blood flow (RBF, ml/gm/min), renal vascular resistance (RVR, units) and mean arterial pressure (MAP, mm Hg) during α and β adrenergic blockade. Group I(n=8) =dogs whose MAP was decreased by LY (10−7M) and Group II(n=6)had Δ MAP<10%). Adenylate cyclase (AC) linkage of D2R occupancy was determined by examining the effects of 10minus;4M forskolin(F) and the D agonists bromocryptine, 10−5M(B), LY 10−4M and (-)-apomorphine, 10−4M(A)on basal or F stimulated AC activity (pmol/mg protein/rain) in main renal artery (MRA) and IRA homogenates. Conclusion: Occupation of renal vascular D2R is associated with increase in RBF without any effect on basal or F stimulated AC. (*p<.05 drug vs. basal, paired t test).