Glycosylated hemoglobins and the oxygen affinity in whole blood

The pO2 at which haemoglobin is half-saturated with oxygen (p50) was determined at fixed pCO2 (45 mmHg) and without altering the resulting pH and the level of organic phosphates in heparinized whole blood samples from 26 diabetic patients and 24 normal subjects of both sexes. Diabetic blood p50 was higher (29.79 +/- 1.68 versus 28.26 +/- 1.16 mmHg, p less than 0.001) and with a higher 2,3-diphosphoglyceric acid/haemoglobin molar ratio (1.04 +/- 0.15 versus 0.86 +/- 0.10, p less than 0.001). The pH at a pCO2 of 45 mmHg was the same in the two groups. The observed p50 values were compared with those obtained after normalization in respect to pH and the level of 2,3-diphosphoglyceric acid. We conclude that glycosylated haemoglobins, known to have an increased affinity for oxygen when purified and in diluted solutions, do not play a significant role in the oxygen affinity pattern of diabetics at the concentrations normally found in vivo.