Glomerular and hormonal responses to dietary protein intake in human renal disease

The effects of dietary protein on glomerular and hormonal function were studied in twelve adults with a variety of glomerular diseases. They were randomly assigned, using a crossover design, to two 11-day periods, one on a high-protein diet (2 g·kg^-1·day^-1) and the other on a low-protein diet (0.55 g·kg^-1·day^-1). Improvement in glomerular permselectivity on the low-protein diet was manifested by a decreased 24-h urinary excretion of total protein, albumin, and IgG by 33, 40, and 25%, respectively (all P < 0.02); a fall in the fractional clearance of albumin (10.1 ± 6.3 x 10^-3 to 5.8 ± 3.3 x 10^-3), and IgG (6.9 ± 5.1 x 10^-3 to 3.5 ± 2.3 x 10^-3) (both P < 0.02); and a decreased fractional clearance of neutral dextrans of molecular radii 48-56 Å (P < 0.05), when measured on the final day of each dietary period. The high-protein diet was accompanied by a higher plasma renin activity (6.9 ± 1.6 vs. 3.5 ± 0.8 ng angiotensin I·ml^-1·h^-1) (P < 0.02), and increased excretion of prostaglandin E and 6-ketoprostaglandin F(1α). We conclude that a low-protein diet rapidly improves the size-selective defect in glomerular permselectivity.