THE EFFECTS OF HIGH-INTENSITY INTERMITTENT EXERCISE ON THE PLASMA-CONCENTRATIONS OF GLUTAMINE AND ORGANIC-ACIDS

Glutamine is an essential substrate for the proper functioning of cell s of the immune system, Falls in plasma glutamine concentration after exercise may have deleterious consequences for immune cell function an d render the individual more susceptible to infection. The purpose of the present study was to examine changes in plasma glutamine concentra tion (measured using a validated enzymatic spectrophotometric method) following an acute bout of intermittent high-intensity exercise, Eight well-trained male games players took part in the study. Subjects repo rted to the laboratory following an overnight fast and performed a 1-h cycle exercise task consisting of 20 1-min periods at 100% maximal O- 2 consumption ((V) over dot O-2max) each separated bq 2 min of recover y at 30% (V) over dot O-2max. Venous blood samples were taken before e xercise and at 5 min, 1 h, 2.5 h, 5 h and 24 h post-exercise. Glutamin e was measured by enzymatic spectrophotometric determination of the am monia concentration before and after treatment of the plasma with glut aminase (EC 3.5.1.2). Plasma glutamine concentration did not fall in t he immediate postexercise period [pre-exercise 681 (23) mu M compared with 663 (46) mu M, at 5 min post-exercise, mean (SEM], but fell to 57 2 (35) mu M at 5 h post-exercise (P < 0.05 compared with pre-exercise) . Plasma lactate concentration rose to 8.8 (1.0) mM at the end of exer cise and fell to 1.8 (0.4) mM at 1 h post-exercise, but plasma concent rations of free fatty acids and beta-hydroxybutyrate both rose substan tially in the post-exercise period (to 240% and 400% of pre-exercise l evels, respectively). The circulating leucocyte count increased signif icantly during exercise (P < 0.01), continued to increase in the hours following exercise and peaked at 2.5 h post-exercise (mainly due to a neutrophilia). The fall in the plasma glutamine concentration at 5 h post-exercise could be due to increased renal uptake of glutamine, whi ch generally occurs in conditions of metabolic acidosis or due to a gr eater removal of glutamine from the plasma resulting from the elevated circulating leucocyte count.