Influence of dietary protein/calorie intake on renal morphology and function in cats with 5/6 nephrectomy.

BACKGROUND: Although still controversial, several studies in humans have suggested That dietary protein restriction may slow the rate of progression of chronic renal failure. Thus, the influence of dietary protein on renal function and progression of renal failure has been the subject of numerous studies in several animal models of chronic renal failure, including rodents, dogs, and baboons. Because of the high incidence of chronic renal failure in aged cats, and the high dietary protein requirements of cats, we studied the effects of dietary protein intake on renal function, proteinuria, and renal morphology in cats with reduced renal mass.

EXPERIMENTAL DESIGN: Partial (5/6) nephrectomy was performed in 14 young adult female cats. Sham surgical procedures were performed in eight control cats. Control cats and cats with 5/6 nephrectomy were randomly assigned to diets containing either 27.6% (low) or 51.7% (high) protein and studied for 1 year.

RESULTS: Renal mass reduction by 5/6 decreased glomerular filtration rate by 2/3 and significantly increased proteinuria. Cats with remnant kidneys had significantly higher systolic and mean blood pressures than control cats. Increased dietary protein/calorie intake significantly increased glomerular filtration rate and proteinuria in all cats. Glomerular filtration rates remained stable in all cats over the year of study. However, high protein/calorie intake resulted in significant renal morphologic injury in remnant kidney cats that was prevented by dietary protein/calorie restriction. Light and electron microscopic glomerular changes in remnant kidney cats fed the high protein diet were similar to changes previously reported in rats and dogs with remnant kidneys.

CONCLUSIONS: Dietary protein/calorie restriction limits proteinuria and glomerular injury in cats with remnant kidneys in a fashion similar to that reported in rats. However, the remnant kidney model in the cat appeared to be associated with a slower rate of progression compared with kidney model in the cat appeared to be associated with a slower rate of progression compared with rats.