In vitro elevation of red blood cell 2,3-diphosphoglycerate with fructose, phosphate, and methylene blue

2,3-Diphosphoglycerate (2,3-DPG) is an important regulator of hemoglobin oxygen affinity and thus can theoretically affect tissue oxygenation. Marked stimulation of DPG with substances that would likely be well tolerated by humans has not been reported previously. In order to achieve such stimulation, we investigated (n = 102) the effect of various combinations of fructose (2.8-11.1 mM) and sodium phosphate (1.0-130.0 mM) on 2,3-DPG production by perfusing fresh human blood in dialysis tubing, 37 degrees C, pH 7.15-7.70, with the appropriate solutions and with compressed air or 100% O2 for up to 6 hours. The DPG increased significantly with fructose/phosphate incubations for 6 hours. At pH greater than 7.35 the average increase was 25%; at pH less than 7.35, 12%; PO4 greater than 6 mM + pH greater than 7.35 yielded the highest changes, 28%. Methylene blue 2.5-7.5 microM + PO4 greater than 2.5 mM + pH greater than 7.35 yielded similar results. Glucose + PO4 showed no effect on DPG. Results were comparable at all fructose levels either with compressed air or 100% O2. Significant elevations in 2,3-DPG were also noted at 4 hours but were of lesser magnitude. In conclusion, significant elevations in 2,3-DPG can be achieved by incubating whole blood with fructose/phosphate solutions or with methylene blue and phosphate for 4-6 hours. It should be possible to adapt these solutions for human use to raise 2,3-DPG. The potential physiologic value of rightward shifts in hemoglobin oxygen affinity can then be tested under appropriate conditions.