Oxygen affinity and Bohr coefficients of dog blood

Abstract

Complete dynamic O2 equilibrium curves (O2EC) on dog whole blood were measured at 25 and 39.degree. C with a spectrophotometric micro blood film technique. O2EC3 were run at 3 CO2 levels (2, 4 and 8%) for each of 3 base excess levels (-10, 0, +10 meq/l). The standard curve (pH 7.4) was determined for saturations 0-0.98. At 39.degree. C, the standard curve O2 pressure at half-saturation (P50) was 31.5 torr; fixed-acid Bohr factor, -0.488; CO2 Bohr factor, -0.498; .DELTA.log P50/.DELTA.log PCO2 [partial pressure], -0.0045. CO2 Bohr slope was linear over the pH range of 7-8. Bohr factors were not significantly saturation-dependent. At 25.degree. C, P50 was 15.4 torr and CO2 Bohr factor -0.647. The temperature coefficient (.DELTA.log P50/.DELTA.T) equaled 0.022. Dog O2EC were shown, with curve-fitting techniques, to be isomorphic with human blood O2EC. The absence of significant oxylabile carbamate formation in dog red blood cells (RBC) was attributed to high 2,3-diphosphoglycerate (DPG) concentrations, 6.23 mM/l RBC, equal to a DPG/Hb4 ratio of 1.12. A simple 2-constant equation S = [(37,900)/(P3 + 205P) +1]-1, where S is saturation and P is O2 tension, was found to fit the dog 39.degree. C standard curve.