AJP - Heart and Circulatory Physiology, Vol 242, Issue 4 500-H506, Copyright © 1982 by American Physiological Society
Postnatal regulation of canine oxygen delivery: control of erythrocyte 2,3-DPG levels
P. A. Mueggler and J. A. Black
The oxygen affinity of canine blood changes markedly following birth. These
changes are correlated with alterations in the intracellular concentration
of 2,3-diphosphoglycerate (2,3-DPG). We have examined the control of
erythrocyte glycolysis by measurements of intracellular enzymes and
intermediates, and we have identified the component responsible for
regulation of 2,3-DPG concentration and hence blood oxygen affinity during
canine postnatal development. The concentration of 2,3-DPG could be
regulated entirely by the enzymes of the Rapoport-Luebering shunt. We have
not detected any alterations in the levels or intracellular activity of
2,3-DPG mutase or 2,3-DPG phosphatase during development; therefore
postnatal changes of 2,3-DPG must be a result of changes in the
intracellular concentrations of 1,3-diphosphoglycerate (1,3-DPG) that are
controlled by other reactions in the glycolytic pathway. Neither low
intracellular concentrations of glucose, the glycolytic substrate, nor an
inherently low glycolytic rate can account for the low 2,3-DPG levels at
birth. 1,3-DPG concentrations and hence 2,3-DPG concentrations are
controlled by the activity of pyruvate kinase, which acts as a glycolytic
sink reaction. The intracellular activity of pyruvate kinase decreases
during the first 50-60 days of age and causes the accumulation of 2,3-DPG.
There is a subsequent change in the in vivo kinetic properties of the
enzyme, giving increased intracellular activity and resulting in the slow
decline of 2,3-DPG concentrations toward normal adult values.
