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 less than 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 less than 0.02); and a decreased fractional clearance of neutral dextrans of molecular radii 48-56 A (P less than 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 less than 0.02), and increased excretion of prostaglandin E and 6-ketoprostaglandin F1 alpha. We conclude that a low-protein diet rapidly improves the size-selective defect in glomerular permselectivity.