Dietary protein and glomerular response to subtotal nephrectomy in the rat

Renal tubules and glomeruli undergo hypertrophy after partial renal ablation. Glomerular and vascular scarring and progressive renal insufficiency may later occur. In the present studies, we have documented the filtration characteristics of glomeruli isolated from rats that had undergone subtotal nephrectomy and been fed a normal protein (NP) diet (24 gm protein per 100 gm chow) or a protein-restricted (PR) diet (6 gm protein per 100 gm chow) and compared these glomeruli to those of sham-operated (SHAM) rats maintained on a normal diet. Body weight of SHAM rats increased by 30% during the 28 weeks of the study. Weight of NP rats did not change significantly, and weight of PR rats decreased by about 25%. Seven weeks after surgery, the glomeruli of NP rats were significantly larger and the ultrafiltration coefficients (Kf) were higher than those of SHAM rats; glomeruli of PR rats were of normal size but also had increased Kf. Twenty-eight weeks after surgery, the glomeruli of rats in each group were larger than at 7 weeks. Kf was no longer elevated in NP rats. Glomerular capillary hydraulic conductivity (Lp) was equal in all groups at 8 days but was increased at 7 weeks and decreased 28 weeks after surgery in NP rats. We hypothesize that glomerular hypertrophy occurs in response to renal ablation and that subsequent changes in the capillary wall lead to diminished Lp. Protein restriction in this model prevents both glomerular hypertrophy and a decrease in Lp.