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

The membrane transport of L-tri-iodothyronine has been studied in human erythrocyte ghosts. Initial uptake showed saturability with a Km 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 Vmax 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.