Erythrocyte 2,3-DPG,PO250% and available O2 during the early post-natal fall in hemoglobin in rabbits

Erythrocyte 2,3-DPG, PO₂50%, whole blood hemoglobin and available O₂, and fixed acid Bohr effect were studied during the first 10 days after birth in rapidly growing suckling rabbits. The post-natal fall in hemoglobin concentration was accompanied by a marked rise in erythrocyte 2,3-DPG and a gradual increase in PO₂50%. The rise in PO₂50% was sufficient to keep the available O₂ of the blood unchanged throughout the observation period. The observations show that a 2,3-DPG mediated rise in PO₂50% very effectively contributes to maintenance of adequate tissue oxygenation during the post-natal fall in hemoglobin. The rise in 2,3-DPG and PO₂50% may be due to the ordinary hypoxia-induced shift to the right of the hemoglobin O₂ dissociation curve, as observed under other circumstances when blood hemoglobin is rapidly reduced, but the very marked rise in 2,3-DPG and the very low Δ PO₂50%/Δ 2,3-DPG ratio suggest that the rise may as well be due to hypoxia independent, pre-programmed processes. The fixed acid Bohr effect was essentially the same in newborn and adult rabbits, and was uninfluenced by large variations in 2,3-DPG.