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

M. E. Rosenberg, J. E. Swanson, B. L. Thomas and T. H. Hostetter Department of Medicine, University of Minnesota, Minneapolis 55455. 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.