Suppressed dopaminergic activity and water-sodium handling in the kidneys at the prehypertensive stage of essential hypertension.

1. In this study, the question of whether the suppression of the renal dopaminergic system is primary or not was investigated. 2. Renal dopaminergic activity was compared between young healthy normotensive subjects without a family history of hypertension (FH(-] and those with a family history of hypertension (FH(+]. 3. A significant decrease in urinary free dopamine excretion was noted, and the responses of urine volume, urinary sodium excretion, and fractional excretion of sodium to infused dopamine were significantly augmented in FH(+). In addition, a normal level of l-dopa delivery at the renal proximal tubules and a significant reduction in the conversion of l-dopa to dopamine in the kidney were found in FH(+). 4. These findings suggest that renal dopaminergic activity is already suppressed at the prehypertensive stage, and that the reduction in the conversion of l-dopa to dopamine in the proximal tubules may contribute to the attenuation of renal dopaminergic activity in FH(+).