An equilibrium model of the oxygen association curve of normal human erythrocytes under standardized conditions.
Hemoglobin-oxygen association curves of human erythrocytes were measured in metabolically stable cells under the standardized conditions of extracellular pH 7.400, carbon dioxide tension 38 mmHg (approximately 5 kPa) and temperature 37 degrees C. A model of the oxygen association curve of normal erythrocytes was subsequently developed, based on assumed equilibrium reactions between hemoglobins (Hb), oxygen, and 2,3-diphosphoglycerate (DPG). Conditional equilibrium constants were determined for reactions leading to the formation of species designated Hb-O2 (K = 0.14 mmHg-1), Hb-(O2)4 (K = 0.44 X 10(-4) mmHg-4), Hb-DPG (K = 0.30 X 10(4) L mol-1) and Hb-O2-DPG (K = 0.61 X 10(2) L mol-1 mmHg-1) for unmodified hemoglobin, and Hb-O2 (K = 0.14 mmHg-1) and Hb-(O2)4 (K = 0.44 X 10(-4) mmHg-4) for glycosylated hemoglobin. This model provides a practical means of calculating the expected oxygen association curve for a sample of erythrocytes under standardized conditions, given the intracellular concentrations of hemoglobins and 2,3-diphosphoglycerate and the assumption that the hemoglobins in those cells function normally.
D002245:Carbon Dioxide; D004163:Diphosphoglyceric Acids / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism*; D004856:Postural Balance; D013696:Temperature
D004163:Diphosphoglyceric Acids; D006454:Hemoglobins; D002245:Carbon Dioxide; D010100:Oxygen