[Sulpiride (stereoisomers, racemic) and dopamine: actions and interactions on renal excretion of hydro-saline].

Renal effects of Dopamine (DA, subpressor dosage 0.1 microgram X kg -1 X min -1) during hypotonic polyuria in moderate hydro-saline retention are variously modified by either d- or l-Sulpiride isomers. In the presence of d-Sulpiride, DA effects, such as an increase in diuresis, free water clearance (CH20) and kaliuresis are suppressed, while increases of saluresis and natriuresis are significantly blunted. In the presence of l-Sulpiride no changes are observed in both saluresis and natriuresis, while decreases occur in diuresis, CH20 and kaliuresis. The inhibitory DA effects on isosmotic sodium reabsorption as a percentage of sodium filtered load are prevented by either isomer as well. A possible role of ineffective renal vascular DA action can be involved in such defective tubular inhibition. However is also suggested a pharmacological blockade of proximal tubular specific DA receptors.