Imbalance of Renal Production Between 5-hydroxytryptamine and Dopamine in Patients with Essential Hypertension Complicated by Microalbuminuria

Background: In the kidney, 5-hydroxytryptamine (5-HT) and dopamine (DA) are formed by the same enzyme, l-aromatic amino acid decarboxylase, but act on renal function and glomerular structure in an opposite direction. The present study was designed to explore whether rates of renal production of 5-HT relative to that of DA are altered in patients with essential hypertension and microalbuminuria.

Methods: We measured urinary levels of 5-HT and DA, reflecting renal production of 5-HT and DA as well as 24-hour ambulatory blood pressure and urinary albumin excretion in 82 consecutive untreated, essential hypertensives without overt proteinuria.

Results: Urinary 5-HT excretion and the ratio of urinary 5-HT to DA were significantly higher in 22 patients with microalbuminuria than in the remaining patients with normoalbuminuria, although urinary DA levels did not differ between the groups. The 24-hour systolic and diastolic blood pressures were also higher in the microalbuminuric group than in the normoalbuminuric group. Multiple regression analysis revealed that urinary 5-HT excretion and 24-hour systolic blood pressure were independently associated with urinary albumin excretion. Furthermore, urinary 5-HT excretion was positively correlated with creatinine clearance as well as blood pressure but tended to be negatively correlated with fractional excretion of sodium.

Conclusions: Renal production of 5-HT is enhanced compared with that of DA in essential hypertensives with microalbuminuria. This imbalance may contribute to the genesis of hypertensive glomerular damage.