Dissociation of renal vasodilator and natriuretic effects of dopamine during sulpiride infusion in normal man.

The effect of sulpiride on dopamine-induced changes in renal function in man has been investigated. Dopamine dose-response studies were performed in 7 healthy volunteers before and after sulpiride 200 mg i.v. The same investigations were performed in 15 healthy volunteers after pretreatment with the selective alpha-1-adrenoceptor antagonist prazosin (n = 7) and the non-selective alpha-adrenoceptor-blocker phentolamine (n = 8). Infusion of dopamine 0.25 to 8 micrograms.kg-1.min-1 resulted in a dose-dependent increase in effective renal plasma flow (ERPF) and glomerular filtration rate (GFR), and a fall in filtration fraction (FF) in 7 normal volunteers. Sulpiride had no effect on base-line ERPF or GFR and did not influence the dopamine-induced renal vasodilatation in those volunteers. It did cause a fall in the fractional sodium excretion (FENa+%) from 1.7 to 1.38, and shifted the dose-response curve of the natriuretic response to a subsequent infusion of dopamine. Sulpiride enhanced the fall in diastolic blood pressure during infusion of dopamine. In 7 other volunteers pretreated with prazosin, sulpiride did not influence base-line ERPF, GFR or FF or their response to dopamine, but the sodium excretion fell markedly (FENa+% changed from 1.13 to 0.63). Administration of sulpiride to 8 volunteers after phentolamine pretreatment 20 mg.h-1 i.v. in the first hour followed by 10 mg.h-1 i.v. resulted in a fall in sodium excretion (FENa+% from 1.09 to 0.53) without affecting ERPF or FF, and it did not affect the dose-response curve in the subsequent DA infusion.(ABSTRACT TRUNCATED AT 250 WORDS)