| Abstract: | Summary. Dopamine (DA) i.v. infused in a low dose (0·1 (μg/kg/min) in healthy women during sustained hypotonic polyuria, produced different renal functional effects as variations in extracellular fluid volume occurred. (1) In hydro-saline retention (n= 23), induced by desoxycorticosterone acetate treatment, DA produced typical vasodilator and hydro-natriuretic effects (Goldberg, 1972). (2) In hydro-saline depletion (n= 19), induced by diuretic treatment and low dietary sodium intake, DA lost its vasodilator and natriuretic efficacy, manifesting, on the other hand, renal sodium conserving effects mainly dependent on the increase in distal sodium reabsorption and a trend towards afferent arteriolar vasoconstriction. (3) Treatment with prazosin (n= 9) or propranolol (n= 9) in hydro-saline depletion, was efficacious in partly restoring the typical vasodilator and natriuretic effects of DA. Thus, in hydro-saline depletion, DA produced sympathomimetic effects which were sufficiently intense to outweigh those due to activation of specific DA renal receptors. |
