Role of renal catecholamines in the control of sodium and water excretion: lack of natriuresis by endogenous dopamine in the rat kidney.

The physiological role of dopamine in renal Na and water excretion was studied in rats treated with L-3,4-dihydroxyphenylalanine (L-DOPA), haloperidol or 6-hydroxydopamine for 1 week. Daily-pooled urine samples, plasma, and kidneys were obtained from the experimental groups and untreated controls. Urinary dopamine was markedly elevated in L-DOPA-treated and transiently decreased in haloperidol-treated rats. Urinary epinephrine, but not norepinephrine was increased in the L-DOPA and haloperidol groups. However, there was no significant difference in urine volume, urinary Na, urinary K, plasma Na and K levels between the experimental groups and controls, except for 6-hydroxydopamine-treated rats. They showed a definite increase in urinary volume, Na, K and aldosterone excretion, whereas the renal norepinephrine and epinephrine content was reduced. Urinary cAMP and Na-K ATPase activity were also similar in all groups, whereas renal cAMP content and aromatic amino acid decarboxylase activity were significantly increased in the L-DOPA and haloperidol groups, suggesting an activated catecholamine synthesis in the kidney. [3H]haloperidol binding was also increased by the L-DOPA and 6-hydroxydopamine administration, but the half maximal displacement dose was similar in all groups (6.4 x 10(-9)mol/l), indicating an increase in the number of dopamine binding sites. These results indicate that 1) in contrast to the pharmacological effect of dopamine, locally-formed dopamine has no direct natriuretic action in the kidney; 2) an enhanced production of dopamine in the kidney does not suppress aldosterone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)