Comparison of the effects of fenoldopam, SK & F R-87516 and dopamine on renal arterioles in vitro.

The ability of the selective DA1 agonists fenoldopam and SK & F R-87516 to relax norepinephrine-contracted afferent and efferent arterioles isolated from rabbit kidney was compared. In both arterioles, fenoldopam and SK & F R-87516 produced a concentration-dependent relaxation with a potency similar to that of dopamine. Fenoldopam also relaxed efferent arterioles contracted with angiotensin II. The selective DA1 receptor antagonist, SK & F R-83566, caused parallel displacements in the concentration-response curves to SK & F 82526, corresponding to dissociation constants of 10.5 and 8.3 nM for afferent and efferent arterioles, respectively. The results provide direct evidence that the dopamine receptor present on renal resistance vessels is of the DA1 subtype.