FUNCTIONAL-CHARACTERIZATION OF ESKIMO DOG HEMOGLOBIN .1. 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 par ameters in Eskimo doss (belonging to Canis lupus familiaris) in Ilulis sat/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 hemoly sate in HEPES buffer at 20 and 37 degrees C revealed a high oxygen aff inity (1.2 mmHg at pH 74, 20 degrees C) in the desalted condition, whi ch decreased markedly in the presence of chloride and 2,3-DPG. A low a pparent 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 chlo ride. Moreover, we show that chloride ions have an additive effect on oxygen affinity in the concentration range 10-300 mmol l(-1) in the pr esence of 3 mmol l(-1) 2,3-DPG at low pH and temperature (pH < 1.4 and 20 degrees C). This feature may be of physiological importance to oxy gen 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 1-' chloride, the Eskimo dog hemoglobin exhibits a low heat of oxygenation, which places this animal close to arctic rum inants with respect to the influence of temperature on oxygen binding in vivo. (C) 1997 Elsevier Science Inc.