Sequential changes in red cell glycolytic enzymes and intermediates and possible control mechanisms in the first two months of postnatal life in lambs.

The sequential changes in several glycolytic enzymes, glucose-6-phosphate dehydrogenase, glycolytic intermediates, and adenosine triphosphate, as well as intracellular pH and plasma inorganic phosphorus were followed simultaneously in eight lambs from birth to 2 months of age. The activities of all glycolytic enzymes and glucose-6-phosphate dehydrogenase were elevated at birth. The 2,3-diphosphoglycerate concentration increased markedly postnatally and was associated with a simultaneous increase in the concentrations of red cell glucose-6-phosphate and total triose phosphate and a decrease in intracellular pH. Inorganic phosphorus also increased and correlated with the 2,3-diphosphoglycerate concentration in the first 10 days of postnatal life. The content of red cell 3-phosphoglycerate, 2-phosphoglycerate, phosphoenolpyruvate, and ATP increased slightly. These results suggested increased glycolytic flux through the diphosphoglycerate mutase reaction which resulted in net synthesis of 2,3-diphosphoglycerate. The red cell total triose phosphate peaked and fell initially, followed by glucose-6-phosphate and 2,3-diphosphoglycerate suggesting inhibition of phosphofructokinase activity and a decrease in glycolysis secondary to decreased red cell intracellular pH. After 10 days of postnatal life all glycolytic intermediates fell simultaneously, which correlated with a decrease in activity of the glycolytic enzymes.