Hemoglobin function in the horse: The role of 2,3 diphosphoglycerate in modifying the oxygen affinity of maternal and fetal blood

Abstract

The blood of the newborn horse was found to have a higher affinity for oxygen than that of the mother. Tis difference was due to the fact that the red cells of newborn foals contained 36% lower 2,3 diphosphoglycerate (2,3 DPG) than red cells from their respective mares. The ATP levels of foal and maternal red cells did not differ significantly. Following birth a prompt rise in the foal's red cell 2,3 DPG occurred, approaching normal (maternal) levels within 5 days. Unlike many other species, the hemoglobins of the newborn and adult horse were shown to be structurally identical. Furthermore, phosphate free solutions of newborn and maternal hemoglobins had identical oxygen saturation curves in the absence and presence of added 2,3 DPG. This study demonstrates that, in contrast to other species, the increased oxygen affinity of horse fetal red cells is due to a lower level of the cofactor 2,3 DPG rather than to the presence of fetal hemoglobin.