A Nonradioactive Uptake Assay for Rapid Analysis of Thyroid Hormone Transporter Function

Area of Science:

• Endocrinology
• Molecular Biology
• Cell Biology

Background:

• Thyroid hormones (TH) cellular uptake is mediated by TH-transmembrane transporters (THTT), a poorly understood regulatory mechanism.
• THTT dysfunction is linked to Allan-Herndon-Dudley syndrome and potential subclinical TH insensitivity.
• Current uptake assays using radiolabeled tracers are limited by handling, safety, and regulatory concerns.

Purpose of the Study:

• To develop a novel, non-radioactive uptake assay for studying thyroid hormone transporters (THTT).
• To establish a reliable, sensitive, and convenient method for THTT functional testing and compound screening.
• To enable high-throughput screening of modulatory compounds on THTT activity in various cell models.

Main Methods:

• Developed a microtiter plate-based assay using non-radioactive iodine-containing substrates.
• Monitored substrate uptake via the Sandell-Kolthoff reaction.
• Validated the assay using monocarboxylate transporter 8 (MCT8)-transfected MDCK1 cells and primary murine astrocytes.

Main Results:

• The novel assay demonstrated reliability, sensitivity, and convenience compared to radioactive methods.
• Successfully measured TH uptake and performed inhibitor screening using bromosulphthalein.
• The method proved applicable to primary murine astrocytes, supporting physiological transporter regulation studies.

Conclusions:

• The developed non-radioactive assay is a safe, inexpensive, and accessible tool for THTT research.
• This method facilitates high-throughput screening for compounds modulating THTT activity.
• Enables functional testing of THTT in basic science and in vitro disease models.