Modulation of antioxidant activities and immune response by food restriction in aging Fisher-344 rats.

Food restriction delays the loss of several cellular immune functions, retards the onset of many diseases during aging and, consequently, extends life span significantly in laboratory rodents. The present study was undertaken to determine whether the age-associated loss in immune function is linked to changes in microsomal and mitochondrial membranes of spleens in Fischer-344 (F-344) male rats. In this study, we determined cytosolic superoxide dismutase activity (SOD), fluidity and cholesterol content in the splenic microsomal and mitochondrial membranes, and DNA synthesis and IL-2 production in spleen cells from young and old ad libitum-fed (AL) and food restricted (FR) rats. The results show that proliferative response to phytohemagglutinin (PHA) and concanavalin A (Con-A) was significantly higher in the spleen cells of 18-month- and 24-month-old FR rats, as compared to their age-matched AL controls. Cytosolic SOD activity in the 24-month-old AL rats decreased by 28% as compared to 6-month-old AL rats, whereas in FR old rats, the loss was only 12%, suggesting that food restriction prevents loss in cytosolic SOD activity in spleens. Our data are consistent with the notion that food restriction modulates loss in immune response of splenocytes by maintaining both cytosolic SOD activity and membrane fluidity during aging.