Thyroid method 2d: Activation of the sodium iodide symporter (NIS) based on Sandell-Kolthoff reaction

Topic: Endocrine disruption

Test Method Number:

TM2019-07 (EU)

Short Name of TM:

NIS-SKR

Year received:

2019

Responsible Organisation:

EURL ECVAM - European Union

General Comments:

Method Description

This method measures the active transport of extracellular iodide across the cellular membrane of cells expressing a functional sodium/iodide (Na+/I-) symporter (NIS), an intrinsic membrane glycoprotein that actively transports iodide from blood into thyroid follicular cells during the initial step of TH synthesis. This method is designed to identify test items that inhibit NIS-mediated iodide uptake by directly competing with iodide for intracellular transport, or indirectly, through an inhibition of Na+/K+ ATPase that disrupts maintenance of the critical cross-membrane sodium gradient required for NIS functionality. Reduction of intracellular iodide is measured as optical density with a spectrophotometric readout following the Sandell-Kolthoff (SK) reaction.
This method was selected with other methods to assess modulating effects on the thyroid system (OECD, 2014). Information on these selected methods is available in TSAR as ‘Thyroid methods’.

Track Approval Status

Submission
Validation
Peer-review
Recommendation
Regulatory acceptance/Standards

Submission

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Date	Stage	Comment	Documents/Links
Jun 2017	Assessment finalised	Selection of the test method for the Thyroid Validation Study based on the OECD scoping document on 'in vitro and ex vivo methods for the identification of modulators of thyroid hormone signalling' and guidance from the Endocrine Disrupters Testing and Assessment Advisory Group considering scientific advances since the issuing of the OECD scoping document, human relevance, possibility for High Throughput screening and availability of method elements (such as reagents and detection method) to a wide range of future users.	OECD scoping document (OECD, 2014)OECD detailed review paper (OECD, 2012)OECD Endocrine Disrupters Testing and Assessment Advisory Group

Validation

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Date	Stage	Comment	Documents/Links
Sep 2019	Finalised	Preparatory work carried out by EURL ECVAM before the start of the validation study between November 2017 and September 2019. During this phase, intellectual property was addressed, legal agreements with method developer, test system supplier and EU-NETVAL laboratory were established, the test system was authenticated, screened for contaminants and information on genetic modification was gathered and adequate training of the EU-NETVAL laboratory was ensured. An outline protocol describing the current status of the method, the quality controlled test system and reference and control items were made available to EU-NETVAL. OECD Good In Vitro Method Practices (GIVIMP, OECD, 2018) has been used as guidance.	OECD Good In Vitro Method Practices (GIVIMP, OECD, 2018)
Apr 2020	Finalised	Start of the EURL ECVAM coordinated validation study. Method developer 'US-EPA (United States of America) and EU-NETVAL facility 'Labfit (Portugal)' agree to assess the method.	EU-NETVAL
Feb 2021	Finalised	Final selection of the validation set chemicals to be used in the thyroid validation study PART 2. Selection was based on the advice provided by 15 experts in in vitro, in vivo and clinical thyroid disruption during an expert meeting in November 2019.
Aug 2021	Ongoing	Method definition and description prior to experimental assessment.
Sep 2021	Planning	PART 1: Assessment of method robustness, reliability and within laboratory reproducibility using few test items.

Peer-review

Recommendation

Regulatory acceptance/Standards