Changes with aging in the modulation of macrophages by norepinephrine

The effect of aging on the norepinephrine (NE)-induced modulation of phagocytic and oxygen-dependent microbicidal processes of mouse peritoneal macrophages was studied. Phagocytosis of latex beads on culture plates and superoxide anion production was evaluated in young (12 weeks), adult (22 weeks), mature (48 weeks) and old (72 weeks) BALB/c mice after in vitro incubation with 10 −12, 10 −9, 10 −7, 10 −5 or 10 −3 M concentrations of NE. The results indicate that the phagocytic response to NE is quite similar in young and mature mice, with increased phagocytosis after incubation with 10 −7 and 10 −3 M, and decreased phagocytosis with 10 −5 M. Macrophages from adult mice increased their phagocytic capacity after incubation with the highest concentrations of NE (10 −5 and 10 −3 M) and macrophages from old animals only were stimulated with 10 −3 M. In addition, it was found that usually NE increased the extracellular superoxide anion production in the absence of phagocytosis in adult mice. No statistically significant changes were found in intracellular superoxide anion levels, but an increase was seen after phagocytosis in macrophages from adult, mature and old animals, especially after incubation with 10 −5 M. In conclusion, the results obtained indicate that the modulation of macrophages by NE does not only depend on the concentration of this neurotransmitter, but also on age.