The position of the
oxygen dissociation curve (ODC) is modulated by
2,3-diphosphoglycerate (2,3-DPG). Decreases in
2,3-DPG concentration within the red cell shift the curve to the left, whereas increases in concentration cause a shift to the right of the ODC. Some earlier studies on diabetic patients have reported that
insulin treatment may reduce the red cell concentrations of
2,3-DPG, causing a shift of the ODC to the left, but the reports are contradictory. Three groups were compared in the present study: 1) nondiabetic control individuals (N = 19);
2) insulin-dependent diabetes mellitus (
IDDM) patients (on
insulin treatment) (N = 19); 3)
non-insulin-dependent diabetes mellitus (
NIDDM) patients using oral
hypoglycemic agents and no
insulin treatment (N = 22). The overall position of the ODC was the same for the three groups despite an increase of the
glycosylated hemoglobin fraction that was expected to shift the ODC to the left in both groups of diabetic patients (HbA1c: control, 4.6%;
IDDM, 10.5%;
NIDDM, 9.0%). In
IDDM patients, the effect of the
glycosylated hemoglobin fraction on the position of the ODC appeared to be counterbalanced by small though statistically significant increases in 2,3-DPG concentration from 2.05 (control) to 2.45 mol/ml blood (
IDDM). Though not statistically significant, an increase of 2,3-DPG also occurred in
NIDDM patients, while red cell
ATP levels were the same for all groups. The positions of the ODC were the same for control subjects,
IDDM and
NIDDM patients. Thus, the PO2 at 50%
hemoglobin-oxygen saturation was 26.8, 28.2 and 28.5 mmHg for control,
IDDM and
NIDDM, respectively. In conclusion, our data question the idea of adverse side effects of
insulin treatment on
oxygen transport. In other words, the shift to the left reported by others to be caused by
insulin treatment was not detected.