Regulation of oxygen affinity in blood of fetal, newborn and adult mouse.

Oxygen half saturation pressure (P50) of blood and the role of 2,3 diphosphoglycerate (DPG), adenosine-triphosphate and red cell pH regulating oxygen affinity were examined in fetuses (16,5-18,5 days of gestational age), neonatal (1-22 days post partum) and adult mice (Balb/c). The high oxygen affinity of fetal blood (P50 = 29 Torr at 37 degrees C, pH 7.4 and Pco2 = 40 Torr) decreases to an average adult value of 41 Torr within two weeks after birth, accompanied by an increase of DPG-concentration from 0.2 M/MHb4 to the average of 1.5 M/MHb4. At a constant pHe of 7.4 red cell pH decreases from pH 7.3 to 7.18 from 18.5 days of gestational age to ten days post partum. Electrophoretic mobility and functional characteristics of purified fetal and adult hemoglobin were identical. Changes in oxygen affinity occur only due to organic phosphate concentration variations. A rapid replacement of large size fetal red cells by smaller adult cells after birth fairly coincides with the increase of the 2,3-DPG concentration.