Effect of training on the phagocytic capacity of peritoneal macrophages from rats exposed to swim stress

Since strenuous effort may affect the immune system, a study was designed t o examine the impact of the progressive training of rats exposed to swim st ress. Rats (trained swimmers) were forced to swim daily in a water bath for progressively longer periods. At the end of the study, which continued for a total of 6 weeks, the superoxide anion generation and phagocytic capacit y of peritoneal macrophages, the mitogen response of splenic cells (splenoc ytes) and the serum corticosterone level were examined. The results, compar ed to those of animals taken in and out of their cages (nonswimmers), showe d an increase in superoxide anion generation, as well as a decrease in both the percentage of phagocytosing cells and the number of particles internal ized by each individual cell. In trained swimmers, the mitogen response to phytohemagglutinin and concanavalin A (Con A), as well as the corticosteron e level, did not change significantly from those of nonswimmers. A third gr oup of animals were forced to swim once only for 30 min, until the appearan ce of signs of marked fatigue (acute swimmers). Their peritoneal macrophage s showed an increased superoxide anion generation and a significantly decre ased response to Con A compared to those of the nonswimmers. The serum cort icosterone level in acute swimmers was found to be increased compared to th at of an additional group of animals kept at complete rest. The findings in dicate that the progressive training of rats exposed to swim stress does no t prevent alterations in certain immune responses, a fact that should be co nsidered by intensive exercisers. Copyright (C) 2000 S. Karger AG, Basel.