The Separate Effects of H+ and 2,3‐DPG on the Oxygen Equilibrium Curve of Human Blood

Abstract

Addition of non-saturating amounts of 2,3-DPG (2,3-diphosphoglycerate) within the red cell (2,3-DPG/Hb < 1) initially reduced Hill''s parameter, n. With increasing 2,3-DPG/Hb, n increased until a maximum was reached at 2,3-DPG/Hb > 1. 2,3-DPG influenced the shape and the position of the whole blood O2 equilibrium curve (OEC). The importance of this effect on the O2 carrying capacity of the blood was considered. The effect of 2,3-DPG on the position of the OEC P50, the O2 pressure at 1/2 maximal O2 saturation) was by way of its allosteric effect on Hb at 2,3-DPG/Hb < 1. Above that ratio, its effect was to reduce intracellular relative to the extracellular pH.