Exhaustive exercise is associated with accelerated generation of reactive oxygen species (ROS) that can result in oxidative stress. We studied the effects of a swimming session on the lymphocyte H₂O₂ production and on the antioxidant response before and after activation with phorbol myristate acetate (PMA). Nine female swimmers made a swimming session of one hour at 80% of their own VO₂max. Blood samples were taken before and 2 hours after finishing the session. Purifyed lymphocytes were incubated 90 min with and without PMA monitorizing the H₂O₂ production. After incubation catalase and glutathione peroxidase were determined. Basal lymphocytes activated with PMA were also treated with inhibitors to detect the main source of ROS: L-NAME (inhibits the nitric oxide synthase), allopurinol (inhibits the xanthine oxidase) and myxothiazol (inhibits the mitochondrial complex III).

No effect of the swimming session was observed in H₂O₂ production and in antioxidant enzyme activities in no-activated lymphocytes. PMA-activation significantly increased the lymphocyte H₂O₂ production, with significant higher production after exercise when compared to pre-exercise values. Catalase and glutathione peroxidase activities significantly increased after exercise in PMA-activated lymphocytes. Lymphocyte ROS production in PMA-activated cells were significantly reduced by myxothiazol, but not by L-NAME or allopurinol. In conclussion, an intense exercise such as a swimming session increases the responsiveness of lymphocytes to PMA by increasing the H₂O₂ production and the antioxidant enzyme activities. The mitochondrial respiratory chain seems the main source of ROS in activated lymphocytes.

This work was granted by the Spanish Ministry of Health (Project DEP2005-00238-CO4-02/EQUI).