RESUMEN
BACKGROUND/AIMS: Modulations in the immune function by stress are a well-known phenomenon. Acute restraint stress may induce impaired T-lymphocyte responses. Moderate physical training is associated with beneficial effects on immunological functions. We investigated the effects of a moderate physical training on T-lymphocyte function in rats submitted to acute restraint stress. METHODS: Thirty male Wistar rats weighing 210-226 g were randomly divided into four groups: non-trained rats (NT, n = 7), and non-trained rats submitted to stress (NT + S, n = 8); trained rats (T, n = 7), and trained rats submitted to stress (T + S, n = 8). Trained rats were submitted to a program of moderate running over a period of 8 weeks. Rats subjected to restraint stress were kept immobilized in glass cylinders (8 cm in diameter and 24 cm long) during 60 min. Plasma corticosterone concentration, peripheral blood leukocyte number, indicators of apoptosis of T lymphocytes in blood and lymphoid organs, and mitogen-induced proliferation of T lymphocytes in lymphoid organs were evaluated. RESULTS: Acute stress exposure raised plasma corticosterone concentration (p < 0.001), but not in previously trained animals. Restraint stress induced an increase in the percentage of lymphocytes in apoptosis, and a decrease in the concanavalin-A-induced proliferation of lymphocytes from the thymus and lymph nodes, and an increase in lymphocytes of the spleen. Neither of these alterations was observed in trained animals submitted to acute restraint stress. CONCLUSIONS: Our data confirm that acute restraint stress is associated with changes in T-lymphocyte function. Moreover, moderate physical training attenuates the effects of acute stress by a mechanism that involves the hypothalamic-pituitary-adrenal axis and an increase in tolerance of leukocytes.
