The Effect of Thyroid Hormones on Erythrocyte 2,3-Diphosphoglycerate:

Erythrocyte 2,3-diphosphoglycerate (2,3-DPG) levels increase in hyperthyroidism. The objective of this study was to investigate the effect of thyroid hormones on red blood cell (RBC) 2,3-DPG levels. Erythrocyte suspensions, prepared from whole blood samples of healthy volunteers, were incubated with 4 ng/mL 3,5,3'-triiodothyronine (T-3) and 0,15 mu g/mL 3,3',5,5'-tetraiodothyronine (T-4) at 37 degrees C for 1 hour. These incubations were also done in the presence of inhibitors that exert effect on the enzymes of the Rapoport-Luebering cycle (RLC) in which 2,3-DPG is formed. Diphosphoglycerate mutase (DPGM) and phosphoglycerate kinase (PGK) were inhibited by N-ethylmaleimide (NEM; 750 mg/L) and suramin (SUR; 3 mmol/L), respectively. Triiodothyronine, T-3 + NEM, and T, + SUR incubations all caused an increase in erythrocyte 2,3-DPG levels compared with controls. When erythrocytes were incubated with T3 in the presence of both inhibitors, however, no increase in 2.3-DPG levels was observed. These data suggest that thyroid hormones may control 2,3-DPG accumulation in RBCs.