EFFECT OF FRUCTOSE INFUSIONS ON OXYGEN-TRANSPORT SYSTEM OF HUMAN-BLOOD

In 9 healthy subjects the erythrocyte 2,3-diphosphoglycerate (2,3-DPG) concentration, which modifies the O2 affinity of Hb, decreased by more than 25% within 60 min of the beginning of a fructose infusion (0.5 g per kg body weight/h1). In contrast erythrocyte ATP concentration was unchanged. In spite of the diminished 2,3-DPG concentrations, the O2 affinity of whole blood actually measured remained unaltered. At the same time, both the arterial and the venous blood pH had fallen by 0.05 or more. In vitro experiments indicated that this fall of erythrocyte 2,3-DPG was not due to a direct effect of fructose on the intra-erythrocytic regulation of 2,3-DPG or to changes indirectly related to the i.v. administration of fructose in vivo, i.e., an increase of the blood lactate/pyruvate ratio or a decrease of plasma inorganic phosphate. Two opposing effects on the O2 transport system of blood were apparently induced by fructose infusions: a displacement of the O2 dissociation curve to the right due to the Bohr effect and a virtually counterbalancing shift of the O2 dissociation curve to the left due to decreased erythrocyte 2,3-DPG concentrations.