Functional characterisation of Eskimo dog hemoglobin: I. Interaction of Cl- and 2,3-DPG and its importance to oxygen unloading at low temperature.
The oxygen binding properties of hemoglobin and some hematological parameters in Eskimo dogs (belonging to Canis lupus familiaris) in Ilulissat/Jacobshavn, Greenland were analysed. The average [2,3-DPG] and [Hb] (n = 16) were 3.14 +/- 0.34 mmol l-1 blood and 9.53 +/- 0.65 g dl-1 (1.49 mmol l-1), respectively, giving a stoichiometric ratio of 2.11 mol 2,3-DPG/mol Hb. Oxygen binding analysis carried out on hemolysate in HEPES buffer at 20 and 37 degrees C revealed a high oxygen affinity (1.2 mmHg at pH 7.4, 20 degrees C) in the desalted condition, which decreased markedly in the presence of chloride and 2,3-DPG. A low apparent equilibrium constant for the binding of 2,3-DPG (1.0 x 10(-5) mol l-1) was found at pH 7.2 and 20 degrees C in the absence of chloride. Moreover, we show that chloride ions have an additive effect on oxygen affinity in the concentration range 10-300 mmol l-1 in the presence of 3 mmol l-1 2,3-DPG at low pH and temperature (pH < 7.4 and 20 degrees C). This feature may be of physiological importance to oxygen unloading under acidotic conditions when tissue temperature is low. Thermodynamic analysis reveal that in the presence of 3 mmol l-1 2,3-DPG and 100 mmol l-1 chloride, the Eskimo dog hemoglobin exhibits a low heat of oxygenation, which places this animal close to arctic ruminants with respect to the influence of temperature on oxygen binding in vivo.
Bårdgard
A J
AJ
Institute of Zoology, University Bergen, Norway. astrid.bardgard@fa.uib.no
Strand
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Nuutinen
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Brix
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D019794:2,3-Diphosphoglycerate; D000818:Animals; D002712:Chlorides / Q000097:blood; D003080:Cold Temperature; D004163:Diphosphoglyceric Acids / Q000097:blood; D004285:Dogs / Q000097:blood*; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D010100:Oxygen / Q000097:blood; D013816:Thermodynamics
D002712:Chlorides; D004163:Diphosphoglyceric Acids; D006454:Hemoglobins; D019794:2,3-Diphosphoglycerate; D010100:Oxygen