Metabolic consequences of differing protein diets in experimental renal disease

Investigation into the effects of two different dietary proteins, casein and soya, fed at isonitrogenous and isocaloric levels, upon renal function, plasma amino acids and serum lipids, in normal and subtotally nephrectomized rats was undertaken. Groups 1 (24% casein, n = 10) and 2 (24% soya, n = 10) were maintained upon the diets for a 10-week period following subtotal nephrectomy, whilst groups 3 (24% casein, n = 6) and 4 (24% soya, n = 5) served as normal controls. Determination of glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and histological analysis were undertaken at the end of the study. Serum lipids and plasma amino acids were determined in subtotally nephrectomized rats (group 5, 24% casein, n = 11: group 6, 24% soya, n = 12) 12 weeks following reduction in renal mass, and serum lipids determined in normal control animals (group 7, 24% casein, n = 10: group 8, 24% soya, n = 10). The glomerular filtration rate and ERPF in normal animals fed casein were significantly greater than those fed soya (P less than 0.01). Survival, proteinuria, renal histological damage and blood urea when killed were all significantly worse in subtotally nephrectomized animals fed casein. Serum cholesterol of groups 5 and 7 fed casein were significantly higher than groups 6 and 8 (P less than 0.05), whilst a significant reduction in serum triglyceride was found for group 6 (P less than 0.001). Plasma amino acids, and essential amino acid ratios of subtotally nephrectomized rats were equivalent, with the exception of plasma glycine (P less than 0.05).