[Effect of nifedipine on proximal tubular function in patients with essential hypertension].

The effect of a single 20 mg sublingual dose of nifedipine on function of proximal tubule of nephron in patients with essential hypertension was studied by measuring changes in renal excretion of water, sodium, uric acid and beta-2-microglobulin (B2m) after nifedipine administration. Fifteen patients at the mean age of 40.1 +/- 7 years, with mild to moderate essential hypertension were studied. Systolic (SBP) and diastolic (DBP) blood pressure as well as heart rate (HR) were recorded every hour. Urine was sampled over 60-min, four times. The first two periods were regarded controls and the last two periods followed the administration of a 20 mg sublingual nifedipine dose. Blood samples were taken 1 h before and 1 h after that. Sodium, uric acid, B2m and creatinine in urine and plasma were determined. Nifedipine caused a significant fall in SBP and DBP (p < 0.001) and a marked increase in HR (p < 0.001). Diuresis, sodium (CNa) and uric acid (Cua) clearances were significantly increased (p < 0.001). Similarly, fractional excretion of sodium (FENa) was higher (p < 0.01). B2m excretion (UB2m) showed a two fold increase after nifedipine administration (p < 0.01). A positive correlations were found between the changes in CNa and Cua (r = 0.835, p < 0.001) and between the changes in UB2m and CNa (r = 0.747, p < 0.001). The results indicate that nifedipine induces an increase in diuresis, natriuresis and excretion of uric acid and B2m. These findings and the relationship between the changes in UB2m and Cua proves effect of nifedipine on proximal tubular function.