Effect of short-term strenuous exercise on erythrocyte 2,3-diphosphoglycerate in untrained men: a time-course study

The literature on the response of erythrocyte 2,3-diphosphoglycerate (2,3-DPG) following exercise is replete with inconsistencies, and recent studies have shown that the time of blood sampling during and following exercise, as well as the duration of exercise, are important in evaluating the response of 2,3-DPG. Experiments were designed to measure the response of 2,3-DPG following short-term strenuous exercise in two groups of untrained men. Twelve men, 19–22 years old (study 1), exercised on a bicycle ergometer at 122.5 W for 10 min and red blood cell (RBC) 2,3-DPG was measured at 0 and 50 min following exercise. The level of 2,3-DPG (mol · ml^–1 RBC) increased after exercise (P < 0.05), but this increase was not significant when 2,3-DPG was expressed as mol · mol^–1 hemoglobin (Hb). However, following 50min of rest, 2,3-DPG (mol · mol^–1 Hb) decreased significantly. In a second group (study 2), nine other men, aged 18–19 years, exercised at the same workload for 15 min and 2,3-DPG was measured at 0, 30, 60, 180, and 330 min respectively after exercise, and no significant mean changes in the level of the phosphate were observed. Findings from these studies suggest that 2,3-DPG does not provide a compensatory adjustment to facilitate oxygen delivery in the hypoxia of short-term strenuous exercise in untrained males immediately following exercise and when recovery intervals of up to 330min are also examined. It is suggested that 2,3-DPG be reported as mol · mol^–1 Hb, since the phosphate exists on Hb in an equimolar ratio in normal physiological states.     

Regulation of red cell 2,3-DPG and Hb-O2-affinity during acute exercise

Summary Reports from the literature and our own data on red cell 2,3-DPG and its importance for unloading O₂ from Hb to the tissues during exhaustive exercise are contradictory. We investigated red cell metabolism during incremental bicycle ergometry of various durations. Furthermore changes in blood composition occurring during exercise were simulated under in vitro conditions. The effect of a moderate (11.2 mmol · l^–1 lactate, pH=7.127) and severe (18 mmol · l^–1 lactate, pH=6.943) lactacidosis on red cell 2,3-DPG concentration was compared with the effect of similar acidosis induced by HCl. Our data indicate that the concentration of 2,3-DPG in red cells depends on the degree of lactacidosis, but not on the duration of exercise. During moderate lactacidosis red cell 2,3-DPG remains unchanged. This can be explained by an interruption of red cell glycolysis on the PK and GAP-DH step caused by a lactate and pyruvate influx into the erythrocyte, as well as an intraerythrocytic acidosis and a drop in the NAD/NADH ratio. During severe lactacidosis and HCL-induced acidosis a decrease in 2,3-DPG due to an inhibition of 2,3-DPGmutase and other glycolytic enzymes can be found. Mathematical correction of the observed P-50 value for the decrease in 2,3-DPG occurring during severe lactacidosis showed that a decrease in Hb-O₂-affinity during strenuous exercise depends on the degree of lactacidosis and temperature elevation.     

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

Summary A statistically significant 10% increase (ps<0.005) in mean red cell 2,3-diphosphoglycerate (2,3-DPG) concentration, concomitantly with a mean 16% increase (p<0.001) in the predicted maximal oxygen uptake (VO₂ max) 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 VO₂ max levels. The mean initial 2,3-DPG level was higher in the subjects with a higher initial VO₂ max. A strenuous but highly aerobic 21-km marching exercise elicited a mean 9% increase (p<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 VO₂ max than in those with a higher pre-test VO₂ max. During another more competitive march 2,3-DPG remained almost unchanged and was associated with a tendency towards a negative correlation with the accompanying lactate response (r=–0.60, p<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.     

Characterization of the pyruvate kinase which induces the low 2,3-DPG level of fetal rabbit red cells

The low 2,3-disphosphoglycerate (2,3-DPG) level of fetal rabbit red cells has been attributed previously to a very high pyruvate kinase (PK) activity. The present report shows that the high PK activity is associated with a distinct fetal isozyme. Fetal and adult rabbit red cell PK were characterized by the methods recommended by the International Committee for Standardization in Haematology. Fetal red cell PK differed from the adult enzyme by its greater thermostability, lower affinities for phosphoenolpyruvate and ADP, higher nucleotide specificity and lower ATP inhibition. Marked electrophoretic differences were not detected. Our results indicate that there is a developmental change in red cell PK isozyme expression in the rabbit. We do not know, however, if this change arises at the gene level or from cell-age dependent postsynthetic modifications of the enzyme. But in view of the role of PK in the control of the 2,3-DPG level and thereby of the oxygen affinity of red blood cells, we assume that the physiological significance of the PK isozyme change is akin to that of the switch from fetal to adult hemoglobin in other species.Abbreviations IU international unit - Hb hemoglobin - PK pyruvate kinase - 2,3-DPG 2,3-diphosphoglycerate - ATP adenosinetriphosphate - PEP phosphoenolpyruvate - F-1,6-diP fructose-1,6-diphosphate - ADP adenosine diphosphate - UDP uridine-diP - GDP guanosine-diP - CDP cytidine-diP - K_0.5 Michaelis constant     

Diurnal changes of the 2,3-diphosphoglycerate concentration in human red cells and the influence of posture

The 2,3-diphosphoglycerate (2,3-DPG) concentration, oxygen half saturation pressure at pH 7.4 (P ₅₀), pH in plasma and red cells, and mean corpuscular hemoglobin concentration (MCHC) of venous blood were determined during unrestricted daily activity (series I) throughout 24 hrs as well as during prolonged bed rest until noon (series II). In series I an almost synchronous diurnal behavior ofP ₅₀, 2,3-DPG, and plasma pH as well as red cell pH became significantly apparent with highest values in the afternoon. The [2,3-DPG] yielded most pronounced alterations, which made up to 13.5% of the average day value. During prolonged recumbency the [2,3-DPG] showed a nonsignificant tendency to decline; theP ₅₀ remained unchanged throughout that period. The possible reason for the missing [2,3-DPG] increase is a reduced change of red cell pH in series II. An influence of a posture dependent aldosterone secretion either directly on the 2,3-DPG metabolism or indirectly via mediating the red cell pH and thus ruling the formation of this organic phosphoris compound is discussed.     

Physiologic effects of normal-or low-oxygen-affinity red cells in hypoxic baboons.

Baboons were bled one-third their red cell mass and were given homologous transfusions of red blood cells to restore the red cell volume. One group of baboons received red blood cells with a normal 2,3-diphosphoglycerate 2,3-DPG) level and normal affinity for oxygen, and in this group the 2,3-DPG level after transfusion was normal. The other group received red blood cells with a 160% of normal 2,3-DPG level and decreased affinity for oxygen, and in this group the 2,3-DPG level after transfusion was 125% of normal. In both groups of baboons, the inspired oxygen concentration was lowered and arterial PO2 tension was maintained at 55-60 mmHg for 2 h after transfusion. During the hypoxic state, systemic oxygen extraction was similar in the two groups, whereas oxygen saturation was lower in the high 2,3-DPG group than in the control animals. Cardiac output was significantly reduced 30 min after the arterial PO2 was restored to normal. These data indicate that red blood cells with decreased affinity for oxygen maintained satisfactory oxygen delivery to tissue during hypoxia.     

Changes in the concentrations of plasma and erythrocyte magnesium and of 2,3-diphosphoglycerate during a period of aerobic training

Physical exercise appears to affect both blood magnesium status and erythrocyte 2,3-diphosphoglycerate (2,3-DPG) concentration. Concentrations of erythrocyte and plasma magnesium (ErMg and PlMg) and erythrocyte 2,3-DPG were measured three times over a period of 2 months in a group of 11 athletes who were training for a marathon. The concentration of 2,3-DPG was found to be significantly increased at the end of the 1st month (P < 0.05) compared to its level at the beginning of the study. However, at the end of the 2nd month, it was significantly lower (P < 0.05) than at the end of the 1st month. This decrease might have been due to the reduction in the intensity of training, despite an increase in the training distance. Both ErMg and PlMg did not change significantly after the 1st and 2nd months of training. However, the decrease of total circulating magnesium, i.e. whole blood magnesium was significant, after both the 1st and 2nd months. This decrease may have been due to an increased loss of magnesium or to a shift of magnesium from the blood to other compartments. We observed a significant negative correlation between ErMg and 2,3-DPG after the 1st month:r = –0.59,P<0.05. We hypothesized that this inverse relationship might have been due to the sympathetic stimulation secondary to physical stress. Furthermore, in view of the mechanism of binding ErMg and 2,3-DPG by haemoglobin, the negative correlation between ErMg and 2,3-DPG might have been due to the relative tissue hypoxia that accompanies aerobic exercise.     

Erythrocyte 2,3-diphosphoglycerate and erythropoietic activity in rabbits with severe bleeding anaemia superimposed on the early post-natal fall in haemoglobin

Erythrocyte 2,3-diphosphoglycerate (2,3-DPG), whole blood haemoglobin (Hb), haematocrit (Hct), mean corpuscular haemoglobin concentration (MCHC) and reticulocyte percentage (Rt) were determined before and after bleeding in two groups of suckling chinchilla rabbits. One group was subjected to severe bleeding on the 12th, 15th, 18th and 21st day after birth and studied for 3 weeks, while the other was studied during the first 24 h after one severe bleeding on the 18th day. In the first group Hb and Hct fell to 2.7 g.dl^-1 and 11.5%, respectively, on the 25th day. The fall was accompanied by a marked rise in Rt and decline in MCHC, reaching maximum and minimum on the 29th day, and a simultaneous, temporary decline in 2,3-DPG. In the other group the acute bleeding was accompanied by a marked fall in Hb and Hct, but no change in Rt and MCHC. 2,3-DPG was unchanged 8 h after the bleeding, but showed a rise during the following 16 h, definitely beyond the normal rise at this age. It is concluded that severe bleeding anaemia induces a rise in erythrocyte 2,3-DPG synthesis. However, the effect of the acute rise in 2,3-DPG is far from sufficient to maintain the O₂ delivery capacity of the blood, and is completely offset by the influence of a subsequent change in the erythrocyte population towards younger cells with low 2,3-DPG.     

Changes in 2,3-diphosphoglycerate (2,3-DPG) after exercise

Summary Previous studies of the influence of physical exercise on erythrocyte 2,3-DPG have shown conflicting results, including that exercise induces increase, decrease or no changes in 2,3-DPG. Assuming that the interplay between the factors governing 2,3-DPG metabolism may change considerably during the early phase of recovery after exercise, the level of erythrocyte 2,3-DPG was examined over a prolonged period of time after heavy exercise in five healthy men, on 3 separate days, the duration of exercise being 6 min, 6 min+6 min with 1 h of rest between, and 60 min, respectively. The short exercise periods were accompanied by a substantial lactate acidosis, whereas the 60 min work was essentially aerobic. With the 6 min work, the erythrocyte 2,3-DPG was unchanged or sligthly reduced immediately after and 15 min after the end of exercise, then rose to a new level, 8% above the initial level, 30 min after the exercise (P<0.001). With the 6+6 min work, the pattern of change followed both bouts of exercise, resulting in a two-step increase of 2,3-DPG, to a new level 12% above its initial value (P<0.001). With the 60 min work, 2,3-DPG was increased after 30 min of exercise, and rose continuously during the early recovery phase, to a new level, 10% above initial value, 45 min after the exercise (P<0.001). With all three types of exercise 2,3-DPG remained unchanged during the following 4 h.Thus, heavy exercise is followed by a definite, slowly developing increase in erythrocyte 2,3-DPG, reaching a new level 30–45 min after exercise.     

2,3-DPG levels in relation to red cell enzyme activities in rat fetuses and hypoxic newborns

We have measured in red cells from fetal and adult Sprague-Dawley and Wistar rats the activities of phosphofructokinase (PFK), pyruvate kinase (PK) and diphosphoglyceromutase (DPGM) as key enzymes in the regulation of 2,3-diphosphoglycerate (2,3-DPG) levels to gather information on the possible causes of the low concentration of 2,3-DPG in fetal red cells. The most striking differences were seen with regard to PK and DPGM activities. The activity of PK was ten times higher in fetal compared to adult red cells, whereas red cell DPGM activity was absent in fetuses and high in adults. In addition, we studied postnatal changes in red cell PK and DPGM activities as well as in the 2,3-DPG concentration in Sprague-Dawley rats. The concentration of 2,3-DPG and the activity of DPGM in red cells increased to almost the adult value within 2 and 4 weeks after birth, respectively, while the activity of PK decreased concomitantly. The postnatal changes occurred similarly, when newborn rats grew up under conditions of hypoxic hypoxia at 0.46 atm (pO₂=9.2 kPa). Our studies support the hypothesis that postnatal changes in 2,3-DPG levels are due to changes in the activity of certain glycolytic enzymes and that the switch from fetal-type to adult-type red cells follows a genetically determined time course.Part of the material presented in this paper has been communicated at the IXth International Berlin Symposium on Structure and Function of Erythroid Cells, 1980     

Physiological changes induced by pre-adaptation to high altitude

To study the physiological effects of pre-adaptation to high altitude, seven subjects were submitted to acclimatization at 4350 m followed by intermittent acclimation in a low barometric pressure chamber (5000 m to 8500 m). The subjects then spent 25 days in the Himalayas. Ventilatory and cardiac responses were studied during a hypobaric poikilocapnic hypoxic test performed both at rest and during exercise (100 W) in normoxia and in hypoxia (barometric pressure: 589 hPa, altitude: 4500 m). Haemoglobin, erythrocytes, reticulocytes, packed cell volume, 2,3-diphosphoglycerate (2,3-DPG) and erythropoietin (EPO) were measured. All variables were studied before pre-adaptation to high altitude (A), after the acclimatization period (B), after the acclimation period (C) and after the expedition (D). The ventilatory and cardiac responses were characterized by an increased tidal volume in hypoxia (+ 33% during exercise in B,P < 0.05; + 100% at rest and + 33% during exercise in C,P < 0.05) without any change in respiratory frequency, whereas an increased systolic blood pressure was only observed in C during exercise in hypoxia [+23 mmHg (3.07 kPa),P<0.01]. Arterial O2 saturation was higher in hypoxia in C and D, both at rest (+8.2% and +4.7%,P<0.01, respectively), and during exercise (+6.3% and +6.3%,P<0.01, respectively). Erythrocytes, haemoglobin and packed cell volume did not vary significantly. The number of reticulocytes was higher in B (+172%,P<0.05) and in C (+249%,P<0.05). EPO and 2,3-DPG increased only in C (+ 770%,P<0.01 and +23%,P<0.05, respectively). These results showed that a combination of continuous pre-acclimatization on Mont Blanc and intermittent acclimation in the hypobaric chamber triggered efficient pre-adaptation mechanisms allowing climbers to save 1 to 2 weeks of acclimatization on the mountain without clinical inconvenience.     

Consequences of 6 weeks of strength training on red cell O2 transport and iron status

Summary Effects of endurance training on OZ transport and on iron status are well documented in the literature. Only a few data are available concerning the consequences of strenuous anaerobic muscular exercise on red cell function. This study was performed to test the influence of strength training alone on parameters of red cell O₂ transport and iron status. Twelve healthy untrained males participated in a strength-training pro gramme of 2-h sessions four times a week lasting 6 weeks. After 6 weeks a small but significant reduction of haemoglobin (Hb; – 5.4 g·l^–1) was found (p<0.05). Mean red cell volume did not change, but a pronounced decrease of mean cell Hb concentration (from 329.2g·l^–1, SE 2.5 to 309.8g·l^–1, SE 1.2;p<0.001) and mean corpuscular Hb (from 29.6 pg, SE 0.4 to 27.7 pg, SE 0.3;p<0.01) was observed. Serum ferritin decreased significantly by 35% (p<0.01); transferrin, serum iron and iron saturation of transferrin were unaltered. Serum haptoglobin concentration was diminished significantly by 30.5% (p<0.01). The reticulocyte count had already increased after 3 weeks of training (p<0.05) and remained elevated during the following weeks. Strength training had no significant influence on the O₂ partial pressure at which Hb under standard conditions was 50% saturated, red cell 2,3-diphospho glycerate and ATP concentration as well as on erythrocytic glutamate-oxalacetate transaminase activity. The data demonstrate that mechanical stress of red cells due to the activation of large muscle masses led to increased intravascular haemolysis, accompanied by a slightly elevated erythropoiesis, which had no detectable influence on Hb-O₂ affinity. Training caused an initial depletion of body iron stores (prelatent iron deficiency). Although Hb had decreased by the end of the training phase a true sports anaemia could not be detected.     

High pyruvate kinase activity causes low concentration of 2,3-diphosphoglycerate in fetal rabbit red cells

1. The high oxygen affinity of fetal blood in rabbits is due to a very low concentration of 2,3-diphosphoglycerate (2,3-DPG) in the red cells. In order to gather informations on the factors responsible for this characteristic we have studied synthesis and break-down of 2,3-DPG in fetal and adult rabbit red cells in vitro and examined possible regulative pathways which may lead to the low 2,3-DPG concentration in vivo. 2. Under conditions where 2,3-DPG and 3-phosphoglycerate (3-PGA) accumulate in adult erythrocytes, i.e. in a solution containing inosine, pyruvate and inorganic phosphate, the amount of 2,3-DPG synthetized in fetal red cells was only 40% of the adult value and 3-PGA was not measurable. Upon inhibition of enolase by NaF, however, both 2,3-DPG and 3-PGA increased to a similar extent in fetal and adult red cells. These findings point towards differences in the pyruvate kinase (PK) reaction which is one of the rate limiting steps of glycolysis. Direct measurements revealed an over tenfold higher PK activity in fetal compared to adult red cells. This higher activity of PK will lead to a decreased concentration of 3-PGA with a consecutive fall in 2,3-DPG concentration. 3. Other factors, like a decreased glucose utilization, a decreased activity of 2,3-DPG mutase or an increased 2,3-DPG phosphatase activity could be excluded as a cause for the low 2,3-DPG concentration in fetal red blood cells. The same holds for extraerythrocytic factors like glucose concentration or pH value in fetal blood. 4. During the postnatal development of rabbits the PK activity decreased. 50 days after birth, PK activity was 20% of the fetal value but still somewhat higher than in adult erythrocytes. This change is paralleled by an increase in 2,3-DPG concentration and half saturation oxygen pressure. With respect to the synthesis of 2,3-DPG and ATP, the fetal rabbit red cell is comparable to hereditary high PK activity in human erythrocytes.     

Erythrocyte 2,3-diphosphoglycerate, PO2 50% and available O2 in rabbits with bleeding anaemia superimposed on the early post-natal fall in haemoglobin

Erythrocyte 2,3-diphosphoglycerate (2,3-DPG), PO2 50%, whole blood haemoglobin (Hb), haematocrit (Hct) and available O2 were determined in two matched groups of suckling rabbits from the 17th to the 34th day after birth. One group was subjected to repeated bleeding, amounting to 1.0-1.5% of the body weight, on day 17, 19, 22 and 25, while the other served as control. The bleeding group had markedly lower Hb and Hct than the control group, which showed the ordinary post-natal fall in Hb. There were, however, no differences between 2,3-DPG and PO2 50% in the two groups. The changes were essentially the same as observed previously in animals in which the post-natal anaemia was avoided by iron-treatment. Thus, these and previously reported data show that the post-natal rise in 2,3-DPG and PO2 50% within wide limits is uninfluenced by marked variations in Hb, even severe bleeding anaemia, and support the assumption that the post-natal rise in 2,3-DPG and PO2 50% is dominated by processes related to the growth and maturation of the animals.     

Red blood cell glutathione peroxidase activity in multiple sclerosis

Summary Glutathione peroxidase (GSH-Px) activity of red blood cells of 23 multiple sclerosis (MS) patients (10 men and 13 women, aged 22–64 years) was examined and compared to the enzyme activity of 26 healthy persons (15 men and 11 women, aged 19–50 years). It was found that the mean GSH-Px activity was significantly higher (P<0.001) in red blood cells of MS patients (39.1±8.1 IU/g Hb) as compared to the group of healthy persons (25.9±5.2 IU/g Hb). There was no difference according to sexes in both the MS patients and the control group. The results are discussed based on the hypothesis that organic peroxides play a role in the etiology of multiple sclerosis.     

Sex differences in the oxygen affinity of hemoglobin

Summary The oxygen dissociation curves of 50 healthy young nonsmokers 25 women and 25 men, were investigated. The following parameters were deter-mined: hemoglobin concentration, microhematocrit, red cell count, mean corpuscular hemoglobin concentration, capillary blood pH,P ₅₀ value, and the concentration of red cell 2,3-diphosphoglycerate. P ₅₀ values are significantly higher in the female group (28.3 mm Hg±0.4 S.E.M.) than in the male group (26.3 mm Hg±0.4 S.E.M.), indicating a lower oxygen affinity of hemoglobin in females.There is no significant difference between the DPG values. No significant negative correlation exists between the Hb concentration and theP ₅₀ values.with the technical assistance of Monika Humpeler and Edith Gasser     

Maximal elevation of 2,3-diphosphoglycerate concentrations in human erythrocytes: Influence on glycolytic metabolism and intracellular pH

Summary The 2,3-DPG content of human red blood cells can be elevated in vitro to a maximum of 24 Moles/g by incubating the cells in media containing inosine, pyruvate and inorganic phosphate (=IPP media). The rate of accumulation depends on the extracellular phosphate level. The concentrations of organic phosphate fractions other than 2,3-DPG also increase during the initial phase of incubation in IPP media, but rediminish thereafter. As a consequence of these changes, the total concentration of acid-soluble organic phosphates in the red cells rises from 14 to 55 Moles P/g red cells. This increase of non-penetrating anions produces a shifting of the Donnan ratio H _e ⁺/H _i ⁺ to lower values and thereby diminishes progressively the intracellular pH of the red cells during incubation in IPP media. The extent of these changes can be calculated on the basis of equations derived by van Slyke.The Donnan induced intracellular acidification causes a gradual impairment of red cell metabolism as the 2,3-DPG concentration increases, thus imposing a selflimitation to the accumulation of 2,3-DPG in the presence of IPP and leading to an inhibition of glucose consumption in IPP-pretreated cells.The findings are discussed with respect to their metabolic and biophysical basis and in view of possible implications for the regulation of red cell metabolism and function.Supported by the Deutsche Forschungsgemeinschaft.     

On the mechanisms of the hypoxia-induced increase of 2,3-diphosphoglycerate in erythrocytes

Summary Hypoxia induces in rats a rather rapid increase of the concentration of 2,3-DPG in red blood cells. This increase is reversed when the animals are returned to normal conditions. Pigeons do not respond to hypoxia with an increase of inositol hexaphosphate concentration in their erythrocytes.In rats exposed for 24 h to gas mixtures containing low oxygen and in addition 5% CO₂ the hypoxia induced rise of 2,3-DPG concentration is abolished. The hemoglobin concentration in whole blood is negatively correlated to red cell 2,3-DPG levels in normal as well as in anemic or polycythemic rats.The rate of 2,3-DPG decomposition in human erythrocytes incubated without glucose is the same in the presence and in the absence of oxygen. The incorporation of³²P into 2,3-DPG proceeds faster in deoxygenated than in oxygenated human red blood cells and exceeds considerably the concomitant acceleration of the glycolytic flux rate. These findings indicate that the rate of 2,3-DPG synthesis becomes enhanced in deoxygenated cells. This is mainly due to an elevation of the intracellular pH; the relief of product inhibition of DPG mutase brought about by a greater binding of 2,3-DPG to deoxyhemoglobin seems to be of minor importance.The regulation of 2,3-DPG concentration by the intraerythrocytic pH as well as by the oxygenation state of hemoglobin and the significance of these regulatory mechanisms in inducing and limiting the changes of red cell 2,3-DPG during hypoxia and anemia are discussed.Preliminary reports of parts of this work were presented at the 36th Meeting of the German Physiological Society, Mainz, September 1969 [11] and at the First International Conference on Red Cell Metabolism and Function, Ann Arbor, October 1969 [23].     

Erythrocyte 2,3-diphosphoglycerate and erythropoietic activity in rabbits with severe bleeding anaemia superimposed in the early post-natal fall in haemoglobin

Erythrocyte 2,3-diphosphoglycerate (2,3-DPG), whole blood haemoglobin (Hb), haematocrit (Hct), mean corpuscular haemoglobin concentration (MCHC) and reticulocyte percentage (Rt) were determined before and after bleeding in two groups of suckling chinchilla rabbits. One group was subjected to severe bleeding on the 12th, 15th, 18th and 21st day after birth and studied for 3 weeks, while the other was studied during the first 24 h after one severe bleeding on the 18th day. In the first group Hb and Hct fell to 2.7 g . dl-1 and 11.5%, respectively, on the 25th day. The fall was accompanied by a marked rise in Rt and decline in MCHC, reaching maximum and minimum on the 29th day, and a simultaneous, temporary decline in 2,3-DPG. In the other group the acute bleeding was accompanied by a marked fall in Hb and Hct, but no change in Rt and MCHC. 2,3-DPG was unchanged 8 h after the bleeding, but showed a rise during the following 16 h, definitely beyond the normal rise at this age. It is concluded that severe bleeding anaemia induces a rise in erythrocyte 2,3-DPG synthesis. However, the effect of the acute rise in 2,3-DPG is far from sufficient to maintain the O2 delivery capacity of the blood, and is completely offset by the influence of a subsequent change in the erythrocyte population towards younger cells with low 2,3-DPG.     

Effects of training on erythrocyte 2,3-diphosphoglycerate in normal men

Summary The erythrocyte 2,3-diphosphoglycerate concentration (2,3-DPG) and the activity of red cell hexokinase, pyruvate kinase, glucose-6 phosphate dehydrogenase and gluthatione reductase were studied in 27 normal volunteers before and after 2 and 4 months of physical endurance training. The 4 months of training increased maximal oxygen uptake and physical working capacity (PWC₁₃₀) by 16% (p<0.001) and 29% (p<0.001) respectively. Resting heart rate was decreased (p<0.001) by 11 beats·min^–1. With 2 months of training the erythrocyte 2,3-DPG concentration increased by 9% (p<0.001); with 4 months training the increase was only 4% (p<0.05). The training-induced increase in red cell 2,3-DPG was not accompanied by enhanced activity of erythrocyte hexokinase, pyruvate kinase, glucose-6 phosphate dehydrogenase or glutathione reductase. It is concluded that the rise in red cell 2,3-DPG induced by physical endurance training is not due to activation of red cell glycolytic enzymes or the enzymes involved in the pentose-phosphate cycle