Bovine Hemoglobin as a Basis for Artificial Oxygen Carriers

Abstract

Under physiological conditions of pH and [CI-] ions the oxygen affinity of bovine hemoglobin is lower than that of human hemoglobin. The difference tends to disappear at low ionic strength, while it increases at high ionic strength. In the presence of CI- ions bovine hemoglobin is not sensitive to 2,3DPG, while in the absence of CI- ions human and bovine hemoglobin respond to 2,3-DPG in a similar way. This is due to a high preferential binding of halogens by the deoxy-conformation in the bovine system. Reaction of deoxy-bovine hemoglobin with 2,3-dibromo-salycyl-fumarate results in a decreased oxygen affinity. Compounds can be purified by anion exchange chromatography which have the sedimentation velocity of tetrameric hemoglobins. They fail to dissociate into dimers at acid pH because of the presence of intramolecular crosslinks. Reverse phase chromatography shows that both kind of subunits are modified by the reaction. The half time of retention in rats of these tetramers is near 5 h. Bovine red cells do not contain 2,3-DPG, therefore they can be stored in the cold in saline for at least 2 months without significant modifications of their oxygen affinity. The oxygen affinity of bovine red cells can be modulated by addition and subtraction of CI- ions from and by changing the pH of the media.