Modulation of red blood cell oxygen affinity with a novel allosteric modifier of hemoglobin is additive to the Bohr effect.

PURPOSE: The Bohr effect describes hemoglobin's affinity for oxygen dependent on solution pH. Within pH range 6.0-8.5, hemoglobin's oxygen affinity decreases with decreasing pH. This results in increased oxygen delivery to metabolically active, acidic tissues and improved oxygen uptake in basic regions including lung tissue. Myo-Inositol tripyrophosphate (ITPP) translocates the erythrocyte membrane and allosterically modifies hemoglobin (Hb). We tested the hypothesis that ITPP does not abrogate the Bohr effect.

METHODS

Experiments were conducted to determine the effect of increasing concentrations of ITPP on P50 with varying pH. We incubated 10 mL red blood cells at 37 °C for 1 h with ITPP concentrations from 0 to 240 mM. The Clark oxygen electrode (Hemox-Analyzer; TCS Scientific, New Hope, PA) determined oxygen affinity of each sample, in triplicate, using buffers pH 6.8, 7.4, and 7.6. A mixed linear regression model with fixed effects for ITPP concentration and pH was used.

RESULTS

Increasing ITPP concentration and decreasing pH increased P50 (p < 0.0001 for ITPP concentration, p < 0.0001 for pH). ITPP modulated increased P50 in normal pH (7.4) and acidic condition pH (6.8); with no effect at alkaline pH (7.6).

CONCLUSION

The Bohr effect is conserved, with ITPP augmenting the decreased oxygen affinity seen with tissue acidosis, while not affecting oxygen affinity in conditions similar to a pulmonary microenvironment.