Effects of acute exercise on lymphocyte subsets and metabolic activity.

Lymphocyte subsets, their responsiveness to mitogen and their capacity for glutamine oxidation and glycolysis were assessed in seven subjects before and after an acute bout of interval exercise, the purpose being to establish whether exercise is associated with alterations in lymphocyte metabolic capacities. The subjects exercised at 112% of their maximal work capacity (as determined by pre-test) on a treadmill and performed 25 repeat tests, each of 1 min duration interrupted by 2 min rest periods. Venous blood samples were taken at rest and 3 min following completion of exercise. Acute exercise was associated with significant decreases in the percentage of T- (p < 0.01) and B-cells (p < 0.01) and an increase in the percentage of NK-cells (p < 0.05). These changes were accompanied by a significant decrease in the responsiveness of peripheral blood lymphocytes to the mitogen concanavalin A (p < 0.05). Acute exercise was also associated with profound changes in the metabolic capacities of peripheral blood lymphocytes: rates of 14CO2 production from [U-14C]glutamine (19%: p < 0.05) and lactate (27%: p < 0.05) production were increased significantly in response to interval exercise. Linear regression analysis revealed significant correlation between the exercise-mediated changes (%) in T- and NK-cells and changes (%) in both lymphocyte responsiveness to concanavalin A and metabolic capacity, particularly glutamine oxidation to CO2. One interpretation of these data is that acute exercise promotes a redistribution in lymphocyte subsets, and that it is this redistribution that is the basis of both the impairment in lymphocyte responsiveness to mitogens and the increase in lymphocyte metabolic capacity, especially glutamine oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

pH, temperature and lactate production in human red blood cells: implications for blood storage and glycolytic control.

The interaction of temperature and pH in biological systems comprises two components. Temperature change may perturb the pH of solutions, and it may change the pKa of some ionizable groups that are involved in enzyme catalysis. The pH optima of single reactions and whole pathways are therefore temperature sensitive. The pH optimum of glycolysis in human red cells has been investigated only at 37 degrees C. We have measured the effect of temperature on the pH of stored blood suspensions and on the pH optimum of glycolysis in the human red cell. The pH of the cell suspensions in a traditional storage medium was 7.25 +/- 0.2 at 4 degrees C. The pH optimum of glycolysis was high (7.8-8.5) between 15 and 35 degrees C. It can be inferred from our data that human red cells are currently stored at least 0.5 pH units below the pH optimum of glycolysis at 4 degrees C. This suggestion is supported by storage experiments which showed that glycolysis at 4 degrees C was at least 1.5-fold more active at an initial pH of 7.67 versus 7.36. Equations which describe the variation in reaction velocity with pH were fitted to the pH curves for glycolysis in order to identify the ionizable groups that contribute to the effect of pH on glycolysis. It is generally accepted that hexokinase catalyses the rate-limiting step in glycolysis in the human red cell, but none of the ionizable groups implicated correspond to that involved in the hexokinase reaction.