3,5-T₂ Stimulates Oxygen Consumption, But Not Glucose Uptake in Human Mononuclear Blood Cells

Summary

L-thyroxine (T₄), L-triiodothyronine (T₃) and 3,5-di-iodothyronine (T₂) rapidly (within 30 min) stimulated oxygen consumption in human mononuclear blood cells, whereas the D isomers of T₄ and T₃ and Triac had no stimulatory effect. Oxygen consumption was stimulated by the same magnitude by equimolar concentrations (5-500 nmol/l) of L-T₄, L-T₃ and 3,5-T₂ reaching a plateau at 100 nmol/l of 0.025 umol/mg DNA × h. The stimulatory effects of T₄ and T₃, but not of T₂ were inhibited by PTU.

Glucose uptake was stimulated only by L-T₄ and L-T₃, whereas 3,5-T₂, Triac and the D-isomers of T₄ and T₃ had no effect. The dose response curve reached an apparent maximum at 100 nmol/l of 0.30 mmol/l × mg DNA × h and PTU had no effect on iodothyronine stimulated glucose uptake.

We conclude that 3,5-T₂ is a significant intracellular stimulator of oxygen consumption, whereas T₃ and T₄ stimulate glucose uptake.

Key words

Deiodinase - Glucose Uptake - Oxygen Consumption - T₂ - T₄ - T₃