To evaluate the role of the renal dopaminergic system on renal water-
sodium metabolism patients with
essential hypertension (EHT), urinary excretion of
dopamine, urinary excretion of
sodium (UNaV) and fractional excretion of
sodium (FENa) were all investigated before and after the administration of
dopamine (3 micrograms/kg/min,
intravenous infusion for 60 minutes),
dopamine antagonist,
metoclopramide (8 mg/m2 BSA,
intravenous injection) or mild
sodium loading in both normotensive subjects and benign EHT. In the basal values, no significant difference in urinary excretion of free (u-fDA), conjugated (u-cDA) or total
dopamine (u-tDA) was found between normotensives and hypertensives. However, low
renin EHT showed a pronounced reduction in u-fDA compared with normotensis subject and (NT) normal
renin EHT. In this study, a significant reduction of u-cDA and of u-tDA was also found in those patients with low
renin essential hypertension. In the normotensive and essential hypertensive groups UNaV or FENa showed a positive correlation with u-fDA (measured simultaneously), but not with u-tDA or u-cDA. The regression line between u-fDA and UNaV or FENa in EHT was shifted towards a lower u-fDA level than in NT. UNaV and FENa were increased by
dopamine infusion and were decreased by
metoclopramide injection in both NT and EHT. Changes of UNaV and FENa following
dopamine or
metoclopramide, showed a negative correlation with u-fDA measured immediately before the administration of these drugs. The enhanced natriuretic response to infused
dopamine and the attenuated antinatriuretic response to injected
metoclopramide were significant in low
renin EHT, when compared with NT or normal
renin EHT patients.(ABSTRACT TRUNCATED AT 250 WORDS)