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Relationship of 2,3-diphosphoglycerate and other blood parameters to training, smoking and acute exercise Marchant, Leonard Roy

Abstract

The purpose of this study was to examine differences in 2,3-diphospho-glycerate concentrations among groups of smokers and nonsmokers, to determine relationships between 2,3-DPG concentrations and other blood parameters affecting oxygen transport, and to examine the effects of acute exercise on 2,3-DPG concentrations. Antecubital venous blood from each subject, before and after exercise, was analyzed for 2,3-DPG, hematocrit, hemoglobin and blood pH. Mean corpuscular hemoglobin concentration (MCHC) was calculated by dividing hemoglobin by hematocrit. Forty university-aged males constituted the sample population. Each subject was assigned to one of five groups, eight subjects per group, based on his status in relation to the variables of physical activity and cigarette smoking. The task consisted of one hour of exercise on a bicycle ergometer at a work rate producing a heartrate of approximately 150 beats per minute (70 per cent of maximal aerobic capacity). Blood samples were taken immediately prior to and immediately following the bout of exercise. A 12 hour fast preceded the work phase of the experiment. The hypotheses were: highly fit subjects have significantly higher 2,3-DPG concentrations and sedentary subjects have significantly lower 2,3-DPG concentrations than moderately fit subjects; smokers have significantly higher 2,3-DPG levels than nonsmokers; exercise produces significant increases in 2,3-DPG; negative relationships exist between 2,3-DPG levels and hemoglobin levels as well as between pre exercise 2,3-DPG levels and change of 2,3-DPG as a result of exercise. A priori orthogonal comparisons of pre exercise red cell 2,3-DPG levels indicated that differences between groups were not significant, i.e. highly fit groups did not demonstrate 2,3-DPG levels significantly higher, nor did sedentary groups demonstrate 2,3-DPG levels significantly lower than moderately fit groups. A definite trend towards higher 2,3-DPG levels was observed as training intensity increased, indicating that the hypothesis of physical training producing an increase in 2,3-DPG levels should not be totally rejected. Demonstration of differences in the carrying capacity of the blood, as reflected by differences in MCHC, hemoglobin and hematocrit, between groups appeared to be related to the trend observed in 2,3-DPG levels. Differences between smokers and nonsmokers in relation to 2,3-DPG concentrations were not significant,indicating that the hypoxia produced through cigarette smoking is not an important stimulator of 2,3-DPG production. Multivariate analysis of results indicated that 2,3-DPG levels were not significantly increased as a result of one hour of exercise at 70 per cent of maximal aerobic capacity. This is indicative of a slow-acting response mechanism affecting 2,3-DPG production, which requires more than one hour, or a more severe stress, to produce a physiological beneficial effect on oxygen transport by the blood. A significant negative correlation was observed between pre exercise levels of 2,3-DPG and hemoglobin levels. This was also reflected in the significant negative correlation between 2,3-DPG and hematocrit and 2,3-DPG and MCHC. A negative correlation was also observed between the change in 2,3-DPG and the change of MCHC that occurred as a result of exercise. The results are interpreted as showing a compensatory effect of 2,3-DPG in producing increased unloading of oxygen when the carrying capacity of the blood is reduced through a reduction in hemoglobin levels. An intimate relationship between 2,3-DPG and MCHC, tending to produce homeostasis in the position of the oxygen dissociation curve of hemoglobin, has been postulated. Changes in 2,3-DPG as a result of exercise were not related to the pre exercise concentration of 2,3-DPG indicating that change of 2,3-DPG is not significantly affected by the amount of 2,3-DPG present before physical activity is initiated.

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