Active transport of L-tri-iodothyronine through the red cell plasma membrane—true or false?

Abstract

The membrane transport of L-tri-iodothyronine has been studied in human erythrocyte ghosts. Initial uptake showed saturability with a K_m of 33.8 nmol/l, suggesting carrier-mediated transport. Ouabain partly inhibited this uptake. ATP, on the other hand, caused a significant increase in the V_max indicating an active transport of L-tri-iodothyronine across the erythrocyte plasma membrane. Ghosts from patients with hyperthyroidism, hypothyroidism or thyroid hormone resistance did not differ significantly from controls in their uptake of the hormone.

Key words:

• adenosine triphosphate
• erythrocyte ghosts
• hyperthyroidism
• hypothyroidism
• ouabain
• thyroid hormone resistance