Hypothermia affects the phagocytic activity of rat peritoneal macrophages

To examine the effect of hypothermia on the phagocytic capacity of rat peritoneal macrophages for latex particles, male Wistar rats were exposed to 4°C for 8 and 72 h. While the shorter exposure to cold did not affect body temperature and macrophage function, animals exposed to 4°C for 72 h showed a mean decrease of their body temperature by 1.5°C. The superoxide anion production was significantly increased whereas the number of phagocytic cells decreased. In addition, the mean number of latex particles engulfed by each individual cell was lower than that of controls. Peripheral blood mononuclear cells (PBMC) of these animals showed lower mitogen response to phytohaemagglutinin (PHA), while that for concanavalin A (Con-A) remained unchanged. Peritoneal macrophages exposed in vitro to 24°C for 60 min showed a decreased phagocytic capacity in comparison with macrophages kept at 37°C, an observation suggesting the development of an indigenous cell defect for phagocytosis at lower temperatures. On the other hand, the effect of additional humoral factor(s) on macrophage activity, such as an increase in serum lever of catecholamines and corticosterone, cannot be excluded. The results of the study may contribute to understanding the predisposition to infections during exposure to cold.