Renal Noradrenergic and Dopaminergic Activity in Patients With Borderline Essential Hypertension

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Abstract
An opposite modulatory influence of renal noradrenergic and dopaminergic activities on sodium excretion has been suggested. In this study urinary noradrenaline (UNA) and dopamine (UDA) excretion were evaluated in patients with borderline essential hypertension (BH; n = 9) and in patients with established essential hypertension (EH; n = 11) as well as in normal subjects (NT, n = 8), during normal sodium and potassium intake. Measurements were performed on fractionated urine collections on two separate days: on the first day under basal conditions and on the second day after saline infusion (SAL), 2L/2h, i.v. In BH, basal UNA and UDA were higher with respect to NT and EH. The difference was significant (p < 0.05) in urine collected between 8 and 14 h. In all three groups, SAL induced a significant decrease in UNA and a significant increase in UDA; the decrease in UNA after SAL was significantly lower in EH in respect to BH and NT. In conclusion, the increased UDA in BH may represent a compensatory mechanism to a defect in sodium excretion, possibly due to elevated renal and/or systemic noradrenergic activity; the normal response to volume and salt loading suggests that the physiological modulation of sympathetic tone is still preserved in BH.