Abstract
Exhausting exercise can have a deleterious effect on the immune system. Nevertheless, the impact of exercise intensity on lymphocyte composition and functionality remains uncertain. The aim of this study was to establish the influence of intensive training on lymphoid tissues (blood, thymus, and spleen) in Wistar rats. Two intensive training programs were performed: a short program, running twice a day for 2 weeks and ending with a final exhaustion test (S-TE group), and a longer program, including two exhaustion tests plus three runs per week for 5 weeks. After this last training program, samples were obtained 24 h after a regular training session (T group), immediately after an additional exhaustion test (TE group) and 24 h later (TE24 group). The composition of lymphocytes in the blood, thymus, and spleen, the function of spleen cells and serum immunoglobulins were determined. In the blood, only the TE group modified lymphocyte proportions. Mature thymocytes’ proportions decreased in tissues obtained just after exhaustion. There was a lower percentage of spleen NK and NKT cells after the longer training program. In these rats, the T group showed a reduced lymphoproliferative activity, but it was enhanced immediately after the final exhaustion. Cytokine secretion was modified after the longer training (T group), which decreased IFN-γ and IL-10 secretion but increased that of IL-6. Higher serum IgG concentrations after the longer training program were detected. In conclusion, the intensive training for 5 weeks changed the lymphocyte distribution among primary and secondary lymphoid tissues and modified their function.
Highlights
It is well-known that the functionality of the immune system can be modified by physical exercise (Nieman, 2011)
Female rats ran for 36–44 min and achieved a maximum speed (∼73 m/min) significantly higher than that of male rats (∼65 m/min), which ran for 33–36 min (Figure 2A)
In the final exhausting test performed after the 5-week training program, the rats ran for 25–42 min at a maximum speed of 61.90 ± 2.22 m/min, which was lower than that achieved in the final exhaustion test carried out by female runner rats from the first training program (P < 0.007)
Summary
It is well-known that the functionality of the immune system can be modified by physical exercise (Nieman, 2011). Practicing moderate activity enhances immune response but overly intense exercise can have a deleterious effect on the immune system (Gleeson, 2007; Leandro et al, 2007) This effect is mainly observed in the recovery period, which may last from 3 to 72 h, and Lymphocytes in Rat Exhausting Exercise increases the susceptibility to pathogens, along with the risk of suffering from infectious diseases of the upper respiratory tract (Nieman, 2009). Immediately after exhausting exercise, there is leukocytosis, as reported both in humans (Suchánek et al, 2010) and rodents (Krüger et al, 2008) This increase in blood leukocytes comprises higher counts of monocytes, granulocytes and the main subsets of lymphocytes, i.e., B and T (Th and Tc) cells (Dimitrov et al, 2010; Neves et al, 2015). It has been shown that the production of immunoglobulins is inhibited after exhausting exercise (Gleeson, 2007; Krüger et al, 2016b)
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