DOPAMINE DA(1) RECEPTORS ON VASCULAR SMOOTH-MUSCLE CELLS ARE REGULATED BY GLUCOCORTICOID AND SODIUM-CHLORIDE

The modulation of dopamine DA(1) receptors of cultured rat renal arterial smooth muscle cells by glucocorticoid and sodium chloride was studied. At a concentration of 10 nM, the synthetic glucocorticoid dexamethasone increased maximum receptor binding but had no effect on the dissociation constant. However, the maximum binding of [H-3]Sch-23390 in cells treated with 100 mM sodium chloride did not change. However, the dissociation constant for DA(1) receptor was increased by adding sodium chloride. The glucocorticoid effect on DA(1) of arterial smooth muscle cells became apparent after hours of incubation in the presence of the steroid and was significantly inhibited by cycloheximide (10 mu g/ml) or by the glucocorticoid receptor antagonist RU-38486, indicating that the effect required protein synthesis through glucocorticoid receptors. Treatment of cells with 1 mu M dexamethasone for 24 h increased basal and DA(1)-stimulated adenylate cyclase activity. Basal adenylate cyclase was decreased by sodium chloride in a dose-dependent manner. These results suggest differential control of DA(1) receptors on vascular smooth muscle cells by glucocorticoid or sodium chloride.