Interrelation between Bohr and temperature effects on the oxygen dissociation curve in men and women

For both sexes (7 males, 7 females) the fixed acid Bohr coefficient BCFA (delta PO2/deltapH) and the temperature coefficient TC (deltalogPO2/deltaT) were investigated in whole blood as function of oxygen saturation (SO2). BCFA which yielded maxima at midsaturation were generally lower at increased temperature (41 degrees C) and in females. Values for 50% SO2 amount to: -0.46 +/- 0.04 SD (males) and -0.37 +/- 0.06 (females) at 37 degrees C, -0.38 +/- 0.09 (MALes) and -0.31 +/- 0.04 (females) at 41 degrees C. TC, too, was generally lower in females, decreased in both sexes at falling pH, but showed no O2-saturation dependency. Mean values were 0.024 +/- 0.008 (males) and 0.017 +/- 0.003 (females) at pH 7.4, 0.019 +/- 0.008 (males) and 0.012 +/- 0.006 (females) at pH 7.2. Sex differences of both TC and BC could also be confirmed in additional experiments. While the interrelation of BC and TC and the variable saturation effect on the coefficients may be referred to known theories about ionization heats of oxylabile groups and nonuniform reactions of the single Hb4(O2)n fractions, respectively, no clear explanation was found for the sex influence.