Thyroid hormone is important for development of various tissues, in particular brain, and for
regulation of metabolic processes throughout life. The follicular cells of the thyroid gland
produce predominantly T4 (thyroxine), but the biological activity of thyroid hormone is largely
exerted by T3 (3, 3′, 5-tri-iodothyronine). The deiodinases involved in T4-to-T3 conversion
or T4 and T3 degradation, as well as the T3 receptors, are located intracellularly. Therefore
the action and metabolism of thyroid hormone require transport of iodothyronines across the …

Transport of thyroid hormone across the cell membrane is required for its action and
metabolism. Recently, a T-type amino acid transporter was cloned which transports aromatic
amino acids but not iodothyronines. This transporter belongs to the monocarboxylate
transporter (MCT) family and is most homologous with MCT8 (SLC16A2). Therefore, we
cloned rat MCT8 and tested it for thyroid hormone transport in Xenopus laevis oocytes.
Oocytes were injected with rat MCT8 cRNA, and after 3 days immunofluorescence …

Cellular entry is required for conversion of thyroid hormone by the intracellular deiodinases
and for binding of 3, 3', 5-triiodothyronine (T3) to its nuclear receptors. Recently, several
transporters capable of thyroid hormone transport have been identified. Functional
expression studies using Xenopus laevis oocytes have demonstrated that organic anion
transporters (eg, OATPs), and L-type amino acid transporters (LATs) facilitate thyroid
hormone uptake. Among these, OATP1C1 has a high affinity and specificity for thyroxine …

Thyroid hormone action and metabolism are intracellular events that require transport of the
hormone across the plasma membrane. We tested the possible involvement of the
Na+/taurocholate cotransporting polypeptide (Ntcp) and organic anion transporting
polypeptide (oatp1) in the hepatic uptake of the prohormone T4, the active hormone T3, and
the metabolites rT3 and 3, 3′-T2. Xenopus laevisoocytes were injected with 2.3 ng Ntcp or
oatp1 cRNA and, after 2–3 days, incubated for 1 h at 25° C with usually 0.1 μM125I-labeled …