Effects of feed restriction and switching the diet on proteinuria in male Wistar rats.

The effects of different dietary regimens on proteinuria in aging male Wistar rats were examined. When rats were given 50% restricted diets from the weanling and young adult (80-days-old) period, they excreted a physiologically normal level of less than 10 mg/day of urinary protein throughout life, and the electrophoretic pattern of their excreted proteins was also normal. This effect of dietary restriction in preventing proteinuria was due to simultaneous restrictions of total energy and protein intake. When rats of middle age (430-days-old) suffering from proteinuria were given 50% restricted diets, their urinary protein excretion decreased rapidly to 20 mg/day, but not further, and then the electrophoretic pattern of their excreted proteins was similar to that of rats with proteinuria. Results on the effect of switching from a commercial diet to 20% casein diet given ad libitum suggested that proteinuria in aging rats may be prevented by dietary control of certain nutrients besides total energy and/or protein intake.