Relationship between the nicotinamide adenine dinucleotide redox potential and the 2,3-diphosphoglycerate content in the erythrocyte in sickle cell disease.

The percentage of nicotinamide adenine dinucleotide (NAD) in the oxidized form [NAD+/(NAD+ and NADH); i.e. the NAD+/NADT ratio] is increased in the red cell (RBC) in sickle cell disease. We tested the hypothesis that the increased NAD+/NADT ratio was a determinant of the increased 2,3-diphosphoglycerate (DPG) content of the SCD RBC. Using normal subjects and individuals with sickle cell disease or autoimmune haemolytic anaemia (AIHA), we observed an inverse relationship between the packed cell volume (PCV) and the RBC DPG concentration (r = -0.69) and a direct relationship between the RBC NAD+/NADT ratio and the DPG concentration (r = 0.74). When the effect of the PCV on DPG was removed using analysis of covariance [DPGady(PCV)], the NAD+/NADT ratio had a significant relationship with the DPGadj(PCV) (r = 0.50, P less than 0.001). In in vitro incubation studies, increasing the NAD+/NADT ratio significantly increased the DPG content of both normal and AIHA RBC. Conversely, decreasing the NAD+/NADT ratio decreased the DPG content of normal, AIHA and SCD RBC. Thus, the increased DPG content in the SCD RBC appears to be due, in part, to the increased NAD+/NADT ratio and is not purely a physiologic response to decreased oxygen carrying capacity.