Reduced hemoglobin affinity for oxygen in venous blood following hemodilution, independent of changes in pH or PCO2.

A rapidly induced and readily reversible shift in the affinity of hemoglobin for oxygen has been demonstrated. The shift, similar to the Bohr effect, is independent of PCO2 or pH changes. It occurred within 30 min of hemodilution and was seen in portal venous blood but not arterial blood. A hypothesis is suggested involving a phasic alteration in levels of 2,3-diphosphoglycerate (DPG) or ATP binding to hemoglobin. It is proposed that, following hemodilution, the degree of these phosphates to hemoglobin increases on passage through the intestinal vascular bed. The increased DPG binding to hemoglobin results in displacement of additional oxygen. As the blood becomes reoxygenated, the levels of DPG-hemoglobin binding decline and DPG is displaced from the hemoglobin by oxygen.