[Sulpiride (stereoisomers, racemic) and dopamine: actions and interactions on renal circulation]

Interaction of sulpiride - both 1- and d- isomers as well as racemic- - with Dopamine (DA, subpressor dosage 0.1 microgram X kg -1 X min -1), on the renal hemodynamic, was studied in DOCA-pretreated men during hypotonic polyuria. P.A.H. and creatinine clearance and renal vascular resistances were determined. In the presence of d-Sulpiride, DA - induced renal vasodilation is carried out gradually and finally reaches similar levels as in the absence of d-Sulpiride. However no glomerular filtration rate increase is produced by DA. In the presence of 1-Sulpiride, DA vasodilating effect is suppressed. On the contrary a trend toward ischemia and a reduction in glomerular filtration rate becomes finally apparent. Stronger binding of 1- than d-Sulpiride with vascular DA receptors in suggested. When both isomers are simultaneously administered (at the nearly total dosage) much less inhibitory effect on DA vasodilator action is observed: it seems that each isomer decreases the affinity on the other isomer for vascular DA receptors.