Elevation of albumin synthesis rates in nephrotic patients measured with [1-13C]leucine.

Eight patients with a nephrotic syndrome and a histologically-proven kidney disease were compared to age- and sex-matched healthy volunteers. Albumin synthesis rates were measured after injection of 13C-labelled leucine (57 mg/kg body wt, 19.4 atoms%). Plasma volume was determined with 125I-albumin. The fractional synthesis rate of albumin was 7.9 +/- 0.4%/day in control subjects in comparison with a marked elevation to 18.4 +/- 2.0%/day (P less than 0.001) in nephrotic patients. The absolute synthesis rate was 145 +/- 9 mg/kg/day in control subjects compared with 213 +/- 17 mg/kg/day (P = 0.005) in the nephrotic patients. There was a statistically significant correlation between ASR and urinary albumin loss (P = 0.035) and serum cholesterol concentration (P = 0.007). The calculated oncotic pressure was significantly lower in the nephrotic group than in the controls (P less than 0.001), but was without correlation with ASR.