[A study on the relationship between natriuresis and renally formed dopamine in the rat].

This study was undertaken to elucidate the relationship between natriuresis and renally formed dopamine in pentobarbital-anesthetized rats that were loaded with 0.9% NaCl. Infusion of dopamine resulted in marked increases in urinary free dopamine excretion, plasma free dopamine concentration, urine volume and urinary sodium excretion. Infusion of carbidopa markedly decreased urinary free dopamine excretion, but did not affect urine volume and urinary sodium excretion. Infusion of L-dopa markedly increased urinary free dopamine excretion and plasma free dopamine concentration, but did not affect urine volume and urinary sodium excretion. When carbidopa was infused with L-dopa or dopamine, carbidopa significantly inhibited the increase in urinary and plasma free dopamine induced by L-dopa, but did not inhibit the increases in urinary and plasma free dopamine, urinary sodium excretion and urine volume induced by dopamine. These data indicated that there is no correlation between renally formed dopamine and natriuresis, and furthermore suggested that renally formed dopamine is not essential for natriuresis.