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 isolated from young (6 mo) and old (24 mo) rats that had free access to food (control group) and from food-restricted old (24 mo) rats that, beginning 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 levels of hsp70 protein and mRNA and the induction of interleukin-2 (IL-2) mRNA by concanavalin A (conA) were measured in these rats. In addition, the percentage of viability (as an index of thermosensitivity) of the lymphocytes from these rats was also measured after exposure of cells to different temperatures (first at 42.5 degrees C and then 45 degrees C). We found that the induction of hsp70 protein and mRNA in lymphocytes isolated from control old rats and food-restricted old rats was lower (P < 0.001) than that in control young rats. However, the levels of hsp70 and mRNA in lymphocytes isolated from food-restricted old rats were similar to the levels in age-matched control rats. Lymphocytes from both control old rats and food-restricted old rats were more thermosensitive than lymphocytes from control young rats; however, thermosensitivity of lymphocytes from food-restricted old rats was similar to that of age-matched control rats. The induction of IL-2 mRNA levels by conA was significantly (P < 0.001) lower in old than in young control rats. In contrast to hsp70, which was not affected by food restriction, the induction of IL-2 mRNA was higher (P < 0.05) in food-restricted old rats than in age-matched control rats. Therefore, food restriction has a differential effect on gene expression.