Endocrine Disruption & Thyroid Hormone Assays

We are experts in regulatory studies for investigative mechanistic toxicology. Our specialist team of scientists offer a suite of endocrine disruptor assays which can be used to compare results across species and interrogate different mechanisms of endocrine modulation, to evaluate the relevance of in vivo toxicology findings:

• Steroidogenesis H295R
• Estrogen transactivation
• Androgen transactivation
• Aromatase assay (Inhibition of CYP19)
• Thyroid hormone modulation assays

Endocrine Disruption Assays

• The AR-EcoScreen™ Androgen Receptor Transactivation Assay (ARTA) is performed in agonism and/or antagonism mode, based on the OECD Guidelines for the Testing of Chemicals, Test No. 458. Cell viability is checked to enable accurate interpretation of results.

Aromatase assay (Inhibition of CYP19; OCSPP 890.1200) - non-GLP

• Aromatase is a cytochrome P450 enzyme responsible for estrogen biosynthesis and converts androgens such as testosterone and androstenedione into estrogens (estradiol and estrone). This assay is run according to OCSPP 890.1200.

Thyroid Modulation Assays

Sodium/Iodide symporter (NIS) assay – in-house assay - GLP or non-GLP

• The NIS is a co-transporter that mediates uptake of iodide into follicular cells of the thyroid gland as the first step in the synthesis of thyroid hormone. This assay is a spectrophotometric method run with a positive control (and negative control if requested by client). Cell viability is also checked to enable accurate interpretation of results.

The NIS assay measures the uptake of iodide into rat FRTL-5 cells in the presence and absence of test item.

Thyroperoxidase (TPO) assay – in-house assay - GLP or non-GLP

• Thyroperoxidase is found in thyroid follicular cells. TPO catalyzes the oxidation and incorporation of iodide into thyroglobulin with subsequent production of thyroid hormones. Differences in species sensitivity to TPO inhibitors are known and thus we perform a cross species set of assays to support interpretation of human relevance.
• The thyroperoxidase (TPO) assay uses thyroid gland microsomal protein from the relevant species (human, rat, dog, pig). TPO activity is determined by monitoring the oxidation of guaiacol using H₂O₂ as a hydrogen donor.

Deiodinase – In house assay - non-GLP

• Deiodination is the major pathway regulating T3 bioavailability in mammalian tissues. The deiodinase suite of assays provides information on thyroid hormone metabolism and measures all iodothyronines (T4, T3, rT3 and T2).
• The Deiodinase assay uses recombinant DIO enzymes (human, rat, dog), ectopically expressed in HEK293 cells. Reaction products are quantified in incubation samples by LC-MS/MS.

Thyroid Hormone Receptor Transactivation Assay – Kit-based - non-GLP

• The Thyroid Hormone Receptor (THR) Transactivation Assay measures the ability of test compounds to transactivate and inhibit thyroid hormone regulated reporter genes by binding to the human thyroid hormone receptor.
• Transactivation of human TRα or human TRβ is measured using non-human mammalian cell lines expressing the appropriate human thyroid hormone receptor and a luciferase reporter system to measure receptor activation. The system can assay either agonism or antagonism at the respective thyroid hormone receptor.