THE IMMUNE-SYSTEM AND SERUM GLUTAMINE DURING A TRIATHLON

This study examined the influence of a triathlon on the immune system and on serum amino acid concentrations. Eight male triathletes swam 25 00 m, bicycled 81 km, and ran 19 km. The concentration of total serum amino acids decreased during the race, with the lowest values occurrin g 2 h postexercise. Similarly, serum glutamine concentration declined from 468 (SEM 24) (prerace) to 318 (SEM 20) mu moll(-1) (2 h postrace) and the natural killer (NK) and lymphokine activated killer (LAK) cel l activities were suppressed 2 h postexercise (P < 0.05). Blood mononu clear cell proliferation decreased during exercise with the lowest val ue observed after running, The leucocyte concentration increased durin g and after exercise due to an increase in the concentration of neutro phils and monocytes. There was no significant change in lymphocyte con centration during or after the exercise. The plasma concentration of i nterleukin-6 did not change and the plasma concentration of interleuki n-1 beta and tumor necrosis factor-alpha were below detection limits, The LAK cell cytotoxicity, but not NK cell activity or proliferative r esponse, was significantly correlated with serum glutamine concentrati ons (r = 0.39, P < 0.01). This study confirms that prolonged endurance exercise results in changes in the cytotoxic function of the NK and L AK cells as well as the proliferative response, The time-course of cha nges in serum glutamine concentrations were best parallelled by change s in LAK cell activities.