Jul 1, 1997

Functional characterisation of Eskimo dog hemoglobin: II. The interplay of HCO(3)- and Cl-

Comparative Biochemistry and Physiology. Part A, Physiology
A J Bårdgard, O Brix

Abstract

Hemoglobin (Hb) from the Eskimo dog (belonging to Canis lupus familiaris) showed similar Bohr effect (delta log P50/delta pH) to human HbA in the presence of 100 mmol l-1 NaCl at 20 degrees C. The presence of 7% carbon dioxide in the desalted condition caused a positive (reversed) Bohr effect in the pH range 7.1-7.5 on Eskimo dog Hb, whereas in human HbA there was no Bohr effect within this pH range. A positive Bohr effect on Eskimo dog Hb in this condition was also observed at 37 degrees C. This could indicate differences in the pK values of the amino terminal residues of the two hemoglobins, with possible pH-dependent binding of both bicarbonate (HCO(3)-) and carbamate. Analysis of the effect of CO2 on oxygen affinity of Eskimo dog Hb in the pH range 6.7-7.6 in the presence of chloride and/or 2,3-diphosphoglycerate (2,3-DPG) support this theory. Our results indicate a competition between HCO(3)- and Cl- in affecting oxygen binding. Thermodynamic analysis reveals that bicarbonate binding lowers the apparent heat of oxygenation in Eskimo dog Hb nearly as much as chloride does in the presence of 2,3-DPG at physiological pH. This safeguards an effective oxygen unloading at lowered red blood cell concentrations of chloride. Moreov...Continue Reading

Mentioned in this Paper

Thermodynamics
Chloride Ion Level
Dioxygen
Alveolar Ventilation Function
Carbamates
Cell Respiration
Myopathy
Oxygen Saturation Measurement
Carbonic Acid Ions
Eskimo dog

About this Paper

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