Low nitrogen diets preserve nutritional status but not residual renal function in rats with severe renal failure

The effects of low nitrogen diets (oral and parenteral) on nutritional status and residual renal function were evaluated in rats with experimentally induced severe renal failure (partial nephrectomy) and compared with the effects of a normal protein diet. Non-uremic rats were used as controls. Muscle protein synthesis was significantly lower in uremic rats fed a normal protein diet than in those fed low protein diets. Values for serum insulin-like growth factor 1 (IGF-1) were significantly lower than for controls in all uremic groups as were the wet and dry weights of skeletal muscle. The glomerular filtration rate was studied after 3 wk of nutritional intervention. Serum creatinine concentration was lower and creatinine clearance greater in uremic rats given the low nitrogen dietary treatments (both oral and parenteral) compared with those fed the normal protein diet. However, the glomerular filtration rate determined with 51Cr-EDTA clearance did not differ between uremic rats with normal and low protein intake. Thus, a low nitrogen diet had positive effects on uremic toxicity and did not compromise nutritional status. The results do not, however, establish a favorable influence on residual renal function and emphasize the need for reliable methods for studying dietary effects on renal function in uremia.