Metabolic and functional changes in lymphocytes and macrophages as induced by ageing

Key enzyme activities of glycolysis, pentosephosphate pathway, Krebs cycle, and glutaminolysis were measured in lymphocytes and macrophages of 3- and 15-month-old rats from the control, thioglycollate-injected, and Walker 256 tumor-implanted groups. The percentage of phagocytosis, phagocytic index, and production of H2O2 in macrophages and the rates of [2-14C]-thymidine and [5-3H]-uridine incorporation in cultured lymphocytes were also determined. The results indicate that the percentage of phagocytosis was not affected but the phagocytic index increased by twofold as a consequence of ageing, whereas the production of H2O2 reduced. The rates of both [2-14C]-thymidine and [5-3H]-uridine incorporation in lymphocytes from aged rats were lower as compared to those of mature animals in the three groups. Taken as a whole, the results of enzyme activities suggest that ageing may reduce the capacity for glucose utilization in lymphocytes and macrophages under the three conditions. Lymphocyte and macrophage glutamine metabolism was not markedly affected by ageing. Therefore, an impaired glucose metabolism during ageing may be one important mechanism for the alteration in lymphocyte proliferation and macrophage phagocytosis observed and also for the modification of the response to inflammatory and tumor challenges.