Influence of Diet and Feed Restriction on Kidney Function of

The influence of diet and feed restriction on kidney function was studied in aging male albino rats. Rats were fed either a commercial feed (LB) or a modified human diet (MHD) from weaning until sacrifice at either 12 or 24 mo. of age. Restricted rats were fed for only 15 out of each 48 hours. Feed restriction during either the first, the second, or both years of life was beneficial in delaying age-associated changes in kidney function as indicated by decreased proteinuria, increased in vitro transport of paraamino-hippuric acid, and reduced incidence and severity of renal lesions. Urinary creatinine and blood urea nitrogen levels were also favorably influenced by restriction. Most parameters were modified by diet as well as by restriction, with MHD being generally associated with improved kidney function. Improve-ment in kidney function may have been more related to a reduction in protein intake than to a reduction in caloric intake as a whole. S IMMS and Berg (1957) listed chron-ic nephrosis and glomerulonephritis as im-portant diseases of aging rats. Feed restriction was shown to reduce the incidence of such lesions. Bras and Ross (1964) also reported a re-duction in prevalence of glomerulonephrosis with restriction of protein, carbohydrate or calories. Adams and Barrows (1963), and Beauchene, Fanestil, and Barrows (1965) re-ported decreased transport of paraamino-hippuric acid (PAH) and alpha-amino iso-butyric acid by kidney slices of old rats. Everitt (1958) and Beauchene, Roeder, and Barrows (1970) reported age-associated increases in pro-teinuria of rats. Recently Burich (1975) re-ported a decreased urine concentrating ability in 700-day-old mice. The present study was undertaken to in-vestigate the influence of diet and feed restric-tion during either the first, the second, or bot