Oxygen release kinetics in healthy subjects and diabetic patients. II: Effects of HbCO.

Glycosylated hemoglobin (HbA1c) and carboxyhemoglobin (HbCO) are elevated in diabetic smokers. Both increase the oxygen affinity of hemoglobin and lower the velocity of oxygen release. We have, therefore, measured the influence of HbCO on the oxygen dissociation kinetics of hemoglobin in blood from healthy subjects (HbA1c = 5.3 +/- 0.3%, n = 12) and diabetic patients (HbA1c = 8.4 +/- 1.6%, n = 12) using the stopped flow technique. In addition, the effect of 2,3-DPG on the oxygen dissociation rate of hemoglobin containing high concentrations of HbCO was examined. Neither statistically nor clinically significant differences in the oxygen dissociation rate between blood from healthy subjects and diabetic patients were found. Increasing the HbCO concentration up to 20% of total hemoglobin produced an approximately 20% decrease (p < 0.001) in the dissociation rate constant in blood samples from both groups of subjects. Addition of 20 mmol 2,3-DPG per 10 mmol hemoglobin had little effect on the magnitude of these changes. It is concluded that HbCO values similar to those present in smokers cause a significant decrease of oxygen release in healthy subjects and diabetic patients. Elevated HbA1c concentrations do not potentiate the effects of HbCO on oxygen release in either group of subjects.