Influence of dietary protein concentration on severity of nephropathy in Fischer-344 (F-344/N) rats.

Nephropathy is an age-related spontaneous disease of most rat strains, and protein content of diet may affect the severity. The purpose of this study was to determine the effect of a 15% protein nonpurified diet on body weight and severity of nephropathy in comparison to a 23% protein NIH-07 diet. Groups of 25 male and 25 female Fischer-344 (F-344) rats, 6 wk of age, were fed the 23 or 15% protein diet ad libitum for 2 yr. Rats were weighed at 1-4-wk intervals, and mean body weights were determined. Water consumption measurements and urinalysis were done at approximately 3-mo intervals during the second year of the study. At the end of the 2-yr study, kidneys from all rats, including those that died or were euthanatized after the eightieth week of the study, were examined by light microscopy and graded for severity of nephropathy as grades 1-4 (minimal, mild, moderate, marked). Growth patterns and the maximum body weights attained by each sex fed the 23 or 15% protein diet were not significantly different. The severity of nephropathy in male rats was significantly higher when fed the 23% protein diet (2.8 moderate to marked) compared to the 15% protein diet (1.3 minimal to mild). The severity of nephropathy in female rats increased slightly when fed the 23% protein diet (1.5 minimal to mild) compared to the 15% protein diet (1.0 minimal).(ABSTRACT TRUNCATED AT 250 WORDS)