The oxygen affinity of chicken haemoglobin in whole blood and erythrocyte suspensions

Studies on avian erythrocyte metabolism. XVI. Accumulation of 2,3-bisphosphoglycerate with shifts in oxygen affinity of chicken erythrocytes

The ability of the chicken erythrocyte to accumulate 2,3-bisphosphoglycerate (2,3-P2-glycerate) and its effect upon the oxygen affinity (P50) of the cell suspensions have been determined. Erythrocytes from chick embryos, which contain 4-6 mM 2,3-P2-glycerate, and from chickens at various ages, which contain 3-4 mM inositol pentakisphosphate but no 2,3-P2-glycerate, were incubated with inosine, pyruvate, and inorganic phosphate. Red blood cells from 20-day chick embryos incubated in Krebs-Ringer, pH 7.45, containing 20 mM inosine and 20 mM pyruvate had an increase in 2,3-P2-glycerate from 4.3 to 11.9 mM after 4 h. Importantly, as 2,3-P2-glycerate concentration increased there was a corresponding increase in P50 of the cell suspension. Further, erythrocytes from 9- and 11-week, and 7-, 14-, 24-, and 28-month-old chickens when incubated similarly with inosine and pyruvate accumulated 2,3-P2-glycerate with corresponding increases in P50 of the cell suspensions. The ability of the red cell to accumulate this compound under the incubation conditions used apparently decreases with age of the bird (e.g., 11.9 mM in the 20-day embryo to 1.1 mM in the 28-month-old chicken after 4 h incubation). Despite the presence of significant amounts of inositol-P5, the accumulation of 2,3-P2-glycerate markedly decreases oxygen affinity of the cell suspensions. The delta P50/mumol increase in 2,3-P2-glycerate in the red cells of the 20-day chick embryo after 4 h incubation is 1.5 Torr; conversely, the delta P50/mumol decrease in 2,3-P2-glycerate in the red cells of the 17-day embryo after 6 h incubation in the presence of sodium bisulfite is 2.8 Torr. The demonstrated ability of the chicken erythrocyte to accumulate 2,3-P2-glycerate in response to certain substrates suggests that regulation of concentration of this compound could contribute significantly to regulation of blood oxygen affinity in birds.

Kinetics of oxygen uptake and release by red blood cells of chicken and duck

The specific conductance (G) for O2 transfer by red blood cells (RBCs) of chicken and muscovy duck was measured using the experimental (stopped-flow) and analytical techniques (RBC model) previously applied to human RBC (Yamaguchi, Nguyen Phu, Scheid & Piiper, 1985). Avian RBCs behaved similarly to human RBCs: G values were of similar magnitude; G for O2 uptake decreased with time and increasing O2 saturation; G for O2 release at high levels of dithionite decreased slightly with decreasing O2 saturation; G for O2 release was higher than G for O2 uptake. The deoxygenation kinetics of oxyhaemoglobin in solution was similar for both avian species. The G measured for O2 release at high dithionite concentration, considered to represent a good approximation to intra-erythrocyte O2 diffusion conductance, averaged (in mmol min-1 Torr-1 ml-1 RBC) 0.33 for chicken and 0.25 for duck (at 41 degrees C, pH of the suspension = 7.5, O2 saturation range 0.4-0.8). These species differences can be explained by differences in cell size, the RBC volume averaging 104 micron3 in the chicken and 155 micron3 in the duck. Compared with human RBCs, the G estimates for avian RBCs are somewhat smaller than would be predicted from size differences, which can be explained by the discoid shape of mammalian RBCs which constitutes an advantage compared with the ovoid avian RBC.

Studies on avian erythrocyte metabolism. XIII. Changing organic phosphate composition in age-dependent density populations of chicken erythrocytes

These studies were performed to determine whether the erythrocytes (RBC's) of chickens are able to alter the concentrations of organic phosphates, particularly inositol pentakis (dihydrogen phosphate) (inositol-P5), in response to anemia. Acute anemia with 33.5% reticulocytes (retics) in the peripheral blood of 4-month-old White Leghorn cockerels was produced after two successive days of controlled bleeding. Five populations of RBC's were prepared from blood of these anemic birds based upon age-dependent density by angle rotor centrifugation. The relative increase in age of Fraction 1 (younger cells) through Fraction 5 (oldest cells) was verified by increased hemoglobin concentration and decreased retic count and cell volume. The acid aqueous-soluble phosphates from each RBC fraction were extracted, fractionated by ion exchange column chromatography, and the concentration of inorganic phosphate (Pi), adenosine triphosphate (ATP), and inositol-P5 quantitated by wet-ash phosphate analysis. Determination of Pi, ATP, and inositol-P5 in Fraction 1 (younger cells, 7.4% retics) from the initial (Day 1) blood withdrawn gave 4.3, 5.7, and 18.6 mumoles Pi/ml RBC, respectively. On Day 4 of controlled-bleeding, Pi, ATP, and inositol-P5 concentrations in Fraction 1 (95.1% retics) were 12.7, 10.6, and 12.3 mumoles Pi/ml RBC, respectively. On Day 11, after 1 week recovery from controlled-bleeding, the values for Pi, ATP, and inositol-P5 in Fraction 1 (37.7% retics) were 5.0, 5.4, and 19.0 mumoles Pi/ml RBC, respectively, which were similar to the values before bleeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygen affinity of blood of adult domestic chicken and red jungle fowl

Respiratory properties of blood from adult domestic chicken (White Leghorn) and red jungle fowl (Gallus gallus, ancestor of domestic breeds) at 41 degrees C were investigated. Oxygen affinity was the same in blood of chicken and jungle fowl (P0.5 46.7 Torr at pH 7.5, 41 degrees C, PCO2 about 30 Torr). The Hill coefficient, nH, increased from 2 at oxygen saturation 0.1 to a maximum of 4.11 at saturation 0.8. Leghorn fixed acid and CO2 Bohr coefficients were -0.51 and -0.53, with little variation over the saturation range 0.15-0.95, indicating negligible specific CO2 effect. An nH value of greater than 4 may indicate polymerization of deoxyhemoglobin, comparable to that which occurs in sickle cell hemoglobin. A biphasic equilibrium curve shape (hump at the low end of the oxygen equilibrium curve) was noted in blood having some degree of hemolysis. Factors that may have contributed to the differences between previous investigations of chicken oxygen affinity are discussed.

Haemoglobin concentration and serum erythropoietin in renal dialysis and transplant patients

In patients with chronic renal failure the use of the relatively new dialysis technique of continuous ambulatory peritoneal dialysis (CAPD), unlike other forms of dialysis, is consistently associated with an increase in Hb concentration, but the mechanism remains obscure. We measured Hb, haematocrit, S-erythropoietin and Hb-oxygen affinity in 3 groups of patients with chronic renal failure. (1) Untreated patients starting on haemodialysis. (2) Patients on intermittent peritoneal dialysis changing to CAPD. (3) Patients from the above 2 groups receiving renal transplants. In addition, red cell mass, plasma volume and red cell survival were measured in (2), before starting CAPD and at 6 months. There were distinctly different patterns of change in Hb concentration, Hb-oxygen affinity and S-erythropoietin in the 3 groups of patients. The increase in Hb concentration with CAPD is due to both a fall in plasma volume and an increase in red cell mass, with an increase in red cell survival. There was no change in Hb-oxygen affinity or serum erythropoietin concentration. The improvement in red cell mass and survival may be related to increased clearances of substances with mol. wt.s between 500 and 5000 daltons which accumulate in renal failure (uraemic middle molecules).

Erythrocytic phosphates and flying activity in birds

1. The intraerythrocitary organic phosphates in different avian species (Sturnus vulgaris, Apus apus, Gallus gallus domesticus, Coturnix coturnix japonica and Columba livia) were analyzed by ionic exchange chromatography. The chromatograms of these species revealed the presence of ADP, ATP, GTP, IPP and inorganic phosphate. 2. The main organic phosphates (ATP and IPP) and the inorganic phosphate were also evaluated, directly, in other specimens. The IPP levels were very similar in all species; however, for ATP, there were great differences, with the lowest value in chickens (1.53 mumol/ml) and the highest value in starlings (5.58 mumol/ml). 3. A progressive training program for homing pigeons with flights from 80 to 760 km did not cause significant variations in IPP levels. Nevertheless, the ATP concentration values showed significant changes. 4. A specific relationship between the flying habits in different species of birds or the training exercise for pigeons and the erythrocyte organic phosphates, was not evident. 5. Hematocrit and hemoglobin values showed significant changes during the progressive training program.

Studies on avian erythrocyte metabolism. XII. The synthesis and degradation of inositol pentakis (dihydrogen phosphate)

The pathway(s) of synthesis and degradation of inositol 1, 3, 4, 5, 6 pentakis (dihydrogen phosphate) (inositol-P5), found predominantly in the avian erythrocyte, are unknown. Myo-inositol (inositol), D-glucose, inosine, and phosphate have been studied as potential precursors of inositol-P5 synthesis in chicken erythrocytes. Whole blood from chickens at several ages has been incubated for prolonged periods and the concentration of inositol-P5 measured to determine the ability of the avian erythrocyte to catabolize inositol-P5. Incubation of erythrocyte suspensions from 5-day chicks with [U-14 C]myo-inositol (inositol) for 17 hr lead to the appearance of 19.8% of the radioactivity in the aqueous acid-soluble extract of the erythrocytes (RBC). Fractionation of this extract on an anion exchange column yielded five major radioactive peaks, three of which represent 1) free myo-inositol, accounting for 63.5% of the radioactivity; 2) myo-inositol monokis (dihydrogen phosphate) (inositol-P), representing 1.6% of the radioactivity; and 3) inositol 1, 3, 4, 5, 6 pentakis (dihydrogen phosphate) (inositol-P5), representing 27.0% of the label in the erythrocyte. Sodium fluoride did not inhibit the incorporation of [U-14 C]myo-inositol into inositol-P5. Similar incubations with D-[U-14 C]-glucose and [U-14 C]-inosine yielded no incorporation of radioactivity into inositol-P5. These data are consistent with the interpretation that inositol is the major precursor for synthesis of inositol-P5 in chick red cells. Incubation of whole blood from 1-, 5-, and 42-day chicks and mature birds at 40 C for as long as 72 hr resulted in increases in RBC inorganic phosphate (Pi) thought due primarily to depletion of adenosine triphosphate (ATP). Inositol-P5 content of RBC of 5- and 42-day birds decreased 28 and 20%, respectively, after 72 hr, but no change was noted in inositol-P5 levels of RBC from mature birds. The red cells of the mature bird appear to be unable to catabolize inositol-P5 at significant rates. The apparent inability of the chicken erythrocyte to alter readily its concentration of inositol-P5 suggests that the hemoglobin oxygen delivery system of birds may be less adaptable to changing oxygen requirements by regulating the concentration of hemoglobin modulator than is that of the mammals.

Representative oxygen dissociation curve and equation for the chicken

Because of the considerable variability in the oxygen dissociation curves for chickens reported in the literature, the respiratory physiologist studying avian gas exchange is faced with the dilemma of which curve is representative for the chicken. In order to arrive at a representative curve, data from eight reported curves were compiled and adjusted to the same set of standard conditions of temperature (T), pH, and partial pressure of carbon dioxide (PCO2): T = 42 C, pH = 7.5 PCO2 = 40 torr. The mean PO2 STD (mean +/- SD) versus percent saturation of hemoglobin curve was then determined. The mean data were fitted to an equation representing the oxygen dissociation curve so that for any selected partial pressure of oxygen (PO2) the percent saturation (%SAT) of oxyhemoglobin may be computed. The P50 values for the mean literature and equation curves, respectively, were 47.4 +/- 9.8 and 45.3 Torr. The mean curve with its standard deviations provides a chicken oxygen dissociation curve representative of the literature data to which experimental data may be compared. The equation for the curve enables rapid referral to the representative curve to compute the %SAT, given the PO2 adjusted to the standard conditions.

Chicken oxygen dissociation curve by dynamic tonometry

Oxygen dissociation curves were determined for blood from mature (5 male, 5 female) Single Comb White Leghorn chickens. Blood was oxygenated by bubbling with humidified 95% O2, 5% CO2, 0% N2 at 100 ml/min for 30 min, then gradually deoxygenated with 0% O2, 5% CO2, 95% N2 at 4 ml/min. During deoxygenation .5 ml samples were drawn at 7 in intervals. The PO2, PCO2, and pH were measured polarographically and the content of O2 was measured by gas chromatography. The PO2 was corrected to T = 42 C, pH = 7.5, and PCO2 = 40 Torr. The curves were determined by plotting: 1) PO2 vs. % Saicont based on O2 content of each serial sample as compared to the fully oxygenated blood O2 content, and 2) PO2 vs. duration of dynamic tonometry plots. The curves determined by the two methods of data analysis corresponded closely, the P50 values (x +/- SD) being 36.2 +/- 2.5, 34.3 +/- 3.1 Torr, respectively.

Oxygen affinity of duck blood determined by in vivo and in vitro technique

Half saturation partial pressure of O2,P50, was determined in domestic Muscovy ducks (Cairina moschata) both by in vivo and in vitro techniques. For in vivo determination, blood samples were drawn from the anesthetized, artificially ventilated animals and analyzed both for O2 content, Co2, and O2 partial pressure, Po2. O2 capacity was detemined in arterial samples during hyperoxic ventilation (arterial Po2 about 180 torr). P50 was calculated from measurements in venous blood samples (O2 saturation near 50%). For in vitro determinations, Co2 was measured in blood samples equilibrated with Po2 close to P50. No significant difference was found between P50 values determined by both techniques. At 41 C and pH 7.50, P50 averaged 41.7 torr when analyzed by in vivo technique and 41.4 torr when determined in vitro. The variability between animals was less than 1 torr (SD) and could be explained by the experimental error. The partially discordant literature data on P50 of duck blood are reviewed and critically discussed.

Haemoglobin Radcliffe (alpha2beta299(Gi)Ala): a high oxygen-affinity variant causing familial polycythaemia

Three members of an Oxfordshire family have polycythaemia. In each case their whole-blood oxygen affinity is increased. This is due to a previously undescribed haemoglobin variant which has been named haemoglobin Radcliffe (alpha2beta299(Gl)Ala). In addition to having a high oxygen affinity haemoglobin Radcliffe shows virtually no haem-haem interaction and a diminished Bohr effect. It is synthesized at the same rate and is as stable as haemoglobin A. X-ray analysis indicates that crystals of deoxyhaemoglobin Radcliffe are isomorphous with those of deoxyhaemoglobin A. Solutions of haemoglobin Radcliffe were also studied by high-resolution proton nuclear magnetic resonance spectroscopy. The structure/function relationships of haemoglobin Radcliffe are discussed in the light of these studies.