The pathogenesis and effect on renal function of nephrocalcinosis induced by different diets in female rats.

The ability of three diets to produce nephrocalcinosis in female rats has been compared after 30, 60 and 90 days of feeding. Severe nephrocalcinosis with associated tubular damage was induced with a standard laboratory maintenance low-protein diet and with a diet containing a single-cell protein (Pruteen) but not with a casein-containing diet. Both the Pruteen and casein diets were high-protein diets. The development of the lesion was equally rapid following feeding of either the laboratory maintenance diet or the Pruteen diet. Nephrocalcinosis was present, with body kidneys similarly affected, at each 30-day interval with either diet. A severe degree of nephrocalcinosis was associated with widespread renal damage although signs of tubular regeneration and repair were evident at 30 days. Nephrocalcinosis induced by the Pruteen diet was accompanied by enlargement of the kidney. Renal function was assessed at each time by the measurement of urine volume, specific gravity and protein content, inulin clearance, and the excretion of the urinary enzymes N-acetyl-beta-glucosaminidase and alkaline phosphatase. Despite extensive calcification and some tubular damage, renal function was unimpaired, reflecting the capacity of the functional reserve of the kidney.