2,3-DPG levels in relation to red cell enzyme activities in rat fetuses and hypoxic newborns

We have measured in red cells from fetal and adult Sprague-Dawley and Wistar rats the activities of phosphofructokinase (PFK), pyruvate kinase (PK) and diphosphoglyceromutase (DPGM) as key enzymes in the regulation of 2,3-diphosphoglycerate (2,3-DPG) levels to gather information on the possible causes of the low concentration of 2,3-DPG in fetal red cells. The most striking differences were seen with regard to PK and DPGM activities. The activity of PK was ten times higher in fetal compared to adult red cells, whereas red cell DPGM activity was absent in fetuses and high in adults. In addition, we studied postnatal changes in red cell PK and DPGM activities as well as in the 2,3-DPG concentration in Sprague-Dawley rats. The concentration of 2,3-DPG and the activity of DPGM in red cells increased to almost the adult value within 2 and 4 weeks after birth, respectively, while the activity of PK decreased concomitantly. The postnatal changes occurred similarly, when newborn rats grew up under conditions of hypoxic hypoxia at 0.46 atm (pO₂=9.2 kPa). Our studies support the hypothesis that postnatal changes in 2,3-DPG levels are due to changes in the activity of certain glycolytic enzymes and that the switch from fetal-type to adult-type red cells follows a genetically determined time course.