Incubation procedure effective for decreasing oxygen affinity of red cells in the dog

Because oxygen affinity of canine red cells had been hardly reduced by the conventional procedure of incubation with inosine-pyruvate-phosphate or dihydroxyacetone-pyruvate-phosphate, incubation with acidified phosphoenolpyruvate (PEP) medium was tested for its effect on oxygen affinity. As this procedure had been shown to induce a significant increase of 2,3-diphosphoglycerate (DPG) in human red cells, it was also proved to be effective for lowering oxygen affinity of canine red cells. Incubation with 15 mM PEP in ACD medium (pH 6.0) at 37 degrees C for 30 min was the standard procedure established after critical scrutiny. The incubated blood exhibited an average increase in half-saturation pressure (P50) amounting to 7 Torr (pH 7.40, Pco2 40 Torr, 37 degrees C), with no appreciable hemolysis and little change in mean corpuscular hemoglobin concentration. Results with Dowex 1-X8 anion exchange chromatography of acid soluble phosphates from the incubated red cells suggested that PEP penetrated rapidly through the canine red cell membrane and was metabolized to DPG via the retrograde process of the Embden-Meyerhof glycolytic pathway.