Effect of long-term training and acute physical exercise on red cell 2,3-diphosphoglycerate

A statistically significant 10% increase (p less than 0.005) in mean red cell 2,3-diphosphoglycerate (2,3-DPG) concentration, concomitantly with a mean 16% increase (p less than 0.001) in the predicted maximal oxygen uptake (VO2max) was observed in 29 recruits, who were studied during 6 months of physical training in military service. The increase in 2,3-DPG was higher, the lower the initial 2,3-DPG and VO2max levels. The mean initial 2,3-DPG level was higher in the subjects with a higher initial VO2max. A strenuous but highly aerobic 21-km marching exercise elicited a mean 9% increase (p less than 0.005) in red cell 2,3-DPG concentration. A significantly greater response of 2,3-DPG to marching exercise was observed in subjects with a lower pre-test VO2max than in those with a higher pre-test VO2max. During another more competitive march 2,3-DPG remained almost unchanged and was associated with a tendency towards a negative correlation with the acccompanying lactate response (r = -0.60, p less than 0.05). Red cell 2,3-DPG response to a standardized exercise is considered to be a suitable indicator for evaluating the effect of training on an individual.     

Red cell 2,3-DPG, ATP, and mean cell volume in highly trained athletes. Effect of long-term submaximal exercise

20 male elite long distance runners were compared to a control group of blood donors to determine the effect of training on red blood cells. The acute effects of exercise on red cells were investigated in 11 of the runners following a race of 15-30 km. The runners had elevated resting values of red cell 2,3-DPG (P less than 0.05) and mean cell volume (P less than 0.01); blood Hb and ATP were not different from concentrations in the control group. The red cell status of the athletes may be explained by an increased proportion of young erythrocytes in runners. No statistically significant changes in red cell 2,3-DPG, ATP, mean cell volume or blood Hb were found post exercise.     

Pronounced influence of Hb-O2 saturation on red cell pH in tench blood in vivo and in vitro

At an extracellular pH of 7.9 the red cell pH in tench blood exhibits a nonlinear, strongly inverse relationship with Hb-O2 saturation, both when investigated in vitro and in vivo (in fish exposed to acid water with and without aluminium). The pHi difference between deoxygenated and oxygenated erythrocytes is large (i.e., 0.35 pH units), which can be accounted for by the Haldane effect and the buffering properties of the blood. The major shift in pHi occurs between 50 and 100% Hb-O2 saturation, indicating an almost full exploitation of the Haldane effect within the normal physiological range of blood O2 saturations.     

Relationship of phosphate administration to serum and red cell phosphate concentration, erythrocyte 2,3-diphosphoglycerate (2,3-DPG) and blood P50 in the hyperglycemic dog

In vitro studies indicate that acute increases in intracellular phosphate concentration decrease red blood cell 2,3-diphosphoglycerate levels (G. Momsen, B. Vestergaard-Bogind, Arch Biochem Biophys 190:67, 1978). We have examined the relationship in vivo of serum phosphate concentration, red cell phosphate, 2,3-DPG and blood P50 in hyperglycemic dogs infused alternately with phosphate or chloride (control) solutions. During the 8-hr insulin infusion, serum phosphate (Pi) fell 40% in the chloride-treated animals and rose 71% in the phosphate-treated dogs (P less than 0.001, phosphate vs. control). RBC Pi concentration declined in the controls and rose significantly in the phosphate-infused dogs (P less than 0.02). Serum Pi and RBC Pi were correlated in the phosphate-managed animals (r = 0.76, P less than 0.02), but not in the controls. RBC 2,3-DPG failed to rise in either group during insulin infusion and regression analysis showed a negative correlation between serum Pi and 2,3-DPG (r = -0.90, P less than 0.005) and between RBC Pi concentration and 2,3-DPG (r = -0.84, P less than 0.02). P50 failed to change in either group during insulin treatment and for up to 24 hr after initiation of the 8-hr infusion of insulin.     

Viability, ATP and 2,3-DPG content of resuspended erythrocytes during several-week storage in cold

Leukocyte-and thrombocyte-poor packed red cells obtained from ACD or. ACD-AG blood were resuspended to a hematocrit of about 55% and stored at 4 degrees C. The resuspension solution consisted of xylitol, inorganic phosphate, bicarbonate, adenine (A) and guanosine (G) solved in water. In one case glucose, citrate and sucrose were also added, in another one, sorbitol. The 2,3-DPG and the ATP level remained for a longer period in the sorbitol-xylitol-medium than in the glucose-xylitol-medium. The ATP content in the red cell suspension was higher than in packed cells. Higher ATP values were obtained in red blood cells from whole blood with adenine and guanosine. The survival rate of resuspended red blood cells in glucose-AG-citrate-sucrose medium was about 80--85% after 3 weeks of storage and 77% after 6 weeks with a higher range.     

Postnatal changes in 2,3-diphosphoglycerate (2,3-DPG) content of calf erythrocytes

In 82 calves, 22 adult cows and 10 fetuses the 2,3-DPG level was determined in the erythrocytes. The lowest level was found in cows (1.13 microM/g haemoglobin, on the average), and in calves aged 35 days or more. In the foetuses the mean 2,3-DPG concentration in the erythrocytes was 4.98 microM/g Hb and it was higher that that in the erythrocytes of cows, the oldest foetuses and calves during the first two days of postnatal life. During 5 weeks of postnatal life the changes taking place in 2,3-DPG concentration could be divided into two periods: period I or the period of increase covering the first 6 days of life, with a characteristic rise in the concentration of this component from 1.37 to 15.80 microM/g Hb, and period II or the period of decrease lasting from the 6th to the 35th day of life. In period II two phases could be discerned, the first phase lasting from the 6th to the 10th day with a steep fall of 2,3-DPG level from 15.80 to 4.58 microM/g Hb, and the second phase from the 10th to the 35th day of life in which the level of 2,3-DPG reached slowly the value found in adult cows. A comparison of oxygen affinity of haemoglobin in calves aged 6 days, which was composed of about 80% of fetal haemoglobin and about 20% of adult haemoglobin, and in adult cows, which contained exclusively adult haemoglobin, showed that the oxygen-binding capacity of haemoglobin was lower in calves.     

Regulation of breathing during exercise

This paper reviewed in short neural and humoral factors which might be responsible for inducing exercise hyperpnea. As one of the neural factors afferent signals which arise in the exercising limbs and are transmitted via group III or IV high threshold sensory fibres were involved. The other neural factor is command signals originating in the central nervous system and being fed onto the respiratory center. Hypothalamic locomotor region is assumed to be a possible locus to integrate these peripheral and central neural signals. There are enough evidences to believe that humoral factors mediated via cardiac output is also essential for the hyperpnea. Changes in VCO2 is well correlated with those of VE in dynamic as well as in steady-state response. Oscillations in PaCO2 can be assumed to play a role to link metabolic CO2 changes to those in ventilation. Thus, no single factor can explain the whole process of exercise hyperpnea. Poon's optimization model may give a key to integrate complicated and coflicting experimental results in a unique concept.     

Erythrocyte 2,3-DPG,ATP and oxygen affinity in hemodialysis patients

Patients on a chronic hemodialysis regimen were studied with respect to their erythrocyte adaptation to anemia. Erythrocyte 2,3-diphosphoglycerate (DPG) concentration was suboptimal compared with that of anemic patients who were not uremic. In uremic patients erythrocyte 2,3-DPG correlated poorly with hemoglobin level but more strongly with plasma pH. Differences between observed levels of erythrocyte 2,3-DPG and the values predicted using data from other anemic patients also correlated with pH. Gradual correction of plasma pH with oral sodium bicarbonate resulted in a substantial increase in erythrocyte 2,3-DPG and a decrease in oxygen affinity. Therefore, maintenance of normal pH in uremic subjects may improve tissue oxygenation. On the other hand, the rapid correction of acidosis during dialysis resulted in increased oxygen affinity. This response was due to the direct effect of pH on oxygen affinity in the absence of a significant change in erythrocyte 2,3-DPG or adenosine triphosphate (ATP) during hemodialysis. Erythrocyte ATP but not 2,3-DPG correlated with serum inorganic phosphate in uremic subjects. A 21% reduction of serum phosphate produced by ingestion of aluminum hydroxide gel had no significant effect on these variables.     

Altitude-induced erythrocytic 2,3-DPG and hemoglobin changes in rats of various ages.

Rats of various ages (2, 12, 24, and 40 mo of age) were exposed for 4 wk to either a simulated high altitude of 23,000 ft or to a Peoria, Ill., altitude of 650 ft above sea level. Hematocrit ratios, hemoglobin, and erythrocytic 2,3-diphospho-glycerate (2,3-DPG) concentrations were measured. Hematocrit and hemoglobin determinations revealed a decrease in erythrocytic content with increasing age, and the augmented erythropoietic response was seen in all age groups of animals as a result of altitude exposure. The maximal erythrocytic content of hemoglobin in the 40-mo-old animals was significantly lower than that of all other age groups. Erythrocytic 2,3-DPG levels were significantly changed by aging alone. In the 40-mo-old group there was a 35% increase over the next highest sea-level value. However, while erythrocytic 2,3-DPG content increased significantly in all other age groups following altitude exposure, it decreased 46% in the 40-mo-old group.     

Regulation of muscle pyruvate metabolism during exercise

Pyruvate dehydrogenase and phosphoenolpyruvate carboxykinase are important enzymes in the regulation of muscle pyruvate metabolism and their in vitro measured activities have been studied in muscle from rested and exercised rats. In addition, the muscle concentration of metabolic intermediates associated with pyruvate metabolism has been measured after exercise. Phosphoenolpyruvate concentration was decreased to less than half the value found in rested muscle but pyruvate concentration did not change. This suggests an increase in the in vivo rate of conversion of phosphoenolpyruvate to pyruvate. Concentrations of malate and aspartate increased two- to threefold which suggests that oxaloacetate concentration was also increased. An increase in oxaloacetate availability would increase acetyl CoA metabolism and therefore would increase pyruvate dehydrogenase activity in vivo. The basal activity of pyruvate dehydrogenase measured in vitro increased approximately twofold after 2 hr of exercise and returned to control values 5 min after the cessation of exercise. Total pyruvate dehydrogenase activity (activated to the maximal extent) was not changed by exercise. Muscle PEPCK activity was also increased during exercise suggesting an increased rate of conversion of oxaloacetate to pyruvate to provide net oxidation of oxaloacetate and other citric acid cycle intermediates. Results of this study demonstrate that the rates of formation and metabolism of pyruvate are increased during exercise.     

Regulation of lactic acid production during exercise

Lactic acid accumulates in contracting muscle and blood beginning at approximately 50-70% of the maximal O2 uptake, well before the aerobic capacity is fully utilized. The classical explanation has been that part of the muscle is O2 deficient and therefore lactate production is increased to provide supplementary anaerobically derived energy. Currently, however, the predominant view is that lactate production during submaximal dynamic exercise is not O2 dependent. In the present review, data and arguments in support of and against the hypothesis of O2 dependency have been scrutinized. Data underlying the conclusion that lactate production during exercise is not O2 dependent were found to be 1) questionable, or 2) interpretable in an alternative manner. Experiments in human and animal muscles under various conditions demonstrated that the redox state of the muscle is reduced (i.e., NADH is increased) either before or in parallel with increases in muscle lactate. Based on experimental data and theoretical considerations, it is concluded that lactate production during submaximal exercise is O2 dependent. The amount of energy provided through the anaerobic processes during steady-state submaximal exercise is, however, low, and the role of lactate formation as an energy source is of minor importance. It is proposed that the achievement of increased aerobic energy formation under conditions of limiting O2 availability requires increases of ADP, Pi, and NADH and that the increases in ADP (and therefore AMP via the adenylate kinase equilibrium) and Pi will stimulate glycolysis, and the resulting increase in cytosolic NADH will shift the lactate dehydrogenase equilibrium toward increased lactate production.