EXPRESSION OF HEAT-SHOCK-PROTEIN-70 IN RAT SPLEEN LYMPHOCYTES IS AFFECTED BY AGE BUT NOT BY FOOD RESTRICTION

The purpose of this study was to determine if food restriction alters the age-related decline in heat shock protein 70 (hsp70) expression in lymphocytes from male Fischer 344 Fats. Spleen lymphocytes were isola ted from young (6 mo) and old (24 mo) rats that had free access to foo d (control group) and from food-restricted old (24 mo) rats that, begi nning at 6 wk of age, were fed 60% (40% food restriction) of the diet consumed by the control rats. Lymphocytes were either heat shocked (42 .5 degrees C for 1 h) or maintained at 37 degrees C (control). The lev els of hsp70 protein and mRNA and the induction of interleukin-2 (IL-2 ) mRNA by concanavalin A (conA) were measured in these rats. In additi on, the percentage of viability (as an index of thermosensitivity) of the lymphocytes from these rats was also measured after exposure of ce lls to different temperatures (first at 42.5 degrees C and then 45 deg rees C). We found that the induction of hsp70 protein and mRNA in lymp hocytes isolated from control old rats and food-restricted old rats wa s lower (P < 0.001) than that in control young rats. However, the leve ls of hsp70 and mRNA in lymphocytes isolated from food-restricted old rats were similar to the levels in age-matched control rats. Lymphocyt es from both control old rats and food-restricted old rats were more t hermosensitive than lymphocytes from control young rats; however, ther mosensitivity of lymphocytes from food-restricted old rats was similar to that of age-matched control rats. The induction of IL-2 mRNA level s by conA was significantly (P < 0.001) lower in old than in young con trol rats. In contrast to hsp70, which was not affected by food restri ction, the induction of IL-2 mRNA was higher (P < 0.05) in food-restri cted old rats than in age-matched control rats. Therefore, food restri ction has a differential effect on gene expression.