Bohr effect induced by CO2 and fixed acid at various levels of O2 saturation in duck blood

The oxygen dissociation curve and Bohr effect were measured in normal whole blood as a function of carboxyhemoglobin concentration [HbCO]. pH was changed by varying CO2 concentration (CO2 Bohr effect) or by addition of isotonic NaOH or HCl at constant PCO2 (fixed acid Bohr effect). As [HbCO] varied through the range of 2, 25, 50, and 75%, P50 was 26.3, 18.0, 11.6, and 6.5 mmHg, respectively. CO2 Bohr effect was highest at low oxygen saturations. This effect did not change as [HbCO] was increased. However, as [HbCO] was increased from 2 to 75%, the fixed acid Bohr factor increased in magnitude from -0.20 to -0.80 at very low oxygen saturations. The effect of molecular CO2 binding (carbamino) on oxygen affinity was eliminated at high [HbCO]. These results are consistent with the initial binding of O2 or CO to thealpha-chain of hemoglobin. The results also suggest that heme-heme interaction is different for oxygen than for carbon monoxide.

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Potential impact of metabolic acidosis on the fixed-acid Bohr effect in snapper (Pagrus auratus) following angling stress

Comparative Biochemistry and Physiology Part A Molecular & Integrative Physiology ◽

10.1016/j.cbpa.2009.04.625 ◽

2009 ◽

Vol 154 (1) ◽

pp. 56-60 ◽

Cited By ~ 7

Author(s):

R.M.G. Wells ◽

B.J. Dunphy

Keyword(s):

Metabolic Acidosis ◽

Bohr Effect ◽

Pagrus Auratus ◽

Potential Impact ◽

Fixed Acid

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Saturation dependency of the Bohr effect: interactions among H-+, CO2, and DPG

Journal of Applied Physiology ◽

10.1152/jappl.1975.38.6.1126 ◽

1975 ◽

Vol 38 (6) ◽

pp. 1126-1131 ◽

Cited By ~ 45

Author(s):

M. P. Hlastala ◽

R. D. Woodson

Keyword(s):

Oxygen Saturation ◽

Base Excess ◽

Oxygen Affinity ◽

Co2 Concentration ◽

Bohr Effect ◽

Blood Oxygen Saturation ◽

Relative Contribution ◽

Lower Oxygen ◽

Lower Saturation ◽

Fixed Acid

The Bohr effect was measured in normal whole blood and in blood with low DPG concentration as a function of oxygen saturation. pH was changed by varying CO2 concentration (CO2 Bohr effect) or by addition of isotonic NaOH or HC1 at constant PCO2 (fixed acid Bohr effect). At nornal DPG concentration CO2 Bohr effect was -0.52 at 50% blood oxygen saturation, increasing in magnitude at lower saturation and decreasing in magnitude at higher saturation. In DPG depleted blood with base excess (BE) similar to 0 meq/1, there was similar dependence of CO2 Bohr effect on oxygen saturation. At BE similar to -10 meq/1, influence of saturation was comparable, but the magnitude of the Bohr effect was markedly increased at all saturations. Fixed acid Bohr effect at normal DPG concentration was -0.45 at saturations of 50–90% but decreased at lower saturations. In DPG-depleted blood fixed acid Bohr effect averaged about -0.33 with minimal variation with saturation. Influence of DPG on oxygen affinity was greater at intermediate saturations and less at saturations below 20% and above 80%. Effect of CO2, independent of pH, was many fold greater at lower oxygen saturations than at higher saturations. These results support the suggestion that the alpha chain of hemoglobin is the site of the initial oxygenation reaction. Physiologically they indicate that the relative contribution of CO2 and fixed acid, as well as the level of oxygen saturation and DPG concentration, may be important in determining PO2 of capillary blood and resulting oxygen delivery.

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