The short-term effects of nifedipine on glomerular hemodynamics, sieving function, and renal tubular function were assessed in 10 patients suffering from biopsy-verified chronic glomerulonephritis. Three weeks of nifedipine treatment after 2 wk of placebo significantly reduced the blood pressure from 153 +/- 6/90 +/- 3 to 139 +/- 6/84 +/- 4 mm Hg (mean +/- SE; P < 0.05). Renal vascular resistance was reduced from 0.54 +/- 0.10 to 0.46 +/- 0.08 mm Hg/mL per minute. However, GFR (44.3 +/- 7 mL/min), effective RPF (265 +/- 37 mL/min), and filtration fraction (0.17 +/- 0.01) remained unchanged. The excretion of albumin of 1,318 +/- 395 micrograms/min was not affected by nifedipine. The glomerular sieving estimated by use of the fractional dextran clearance technique revealed no significant change by nifedipine compared with placebo in the range of 30 to 60 A of hydrodynamic dextran radius. Fractional proximal reabsorption (lithium clearance method) was reduced by nifedipine from 53 +/- 5 to 46 +/- 4% (P < 0.05). Also, the excretion of beta 2-microglobulin and N-acetyl-beta-glucosaminidase increased from 10.98 +/- 4.62 to 11.86 +/- 4.74 mg/24 h (P < 0.05) and from 19.7 +/- 4.2 to 25.3 +/- 7.0 nmol/h per micromoles of creatinine (P = 0.05), respectively. It was concluded that nifedipine treatment acutely represses proximal tubular function but is without significant effect on glomerular sieving and albuminuria in these patients.