Endocrine Disruption: In Vitro Inhibition of Thyroid Peroxidase (TPO)-Catalyzed Iodination using Human Thyroid Microsomes: Mn Metal Powder and MnCl2
This screening study evaluated the effects of two manganese-containing materials, manganese chloride (MnCl₂) and high-purity electrolytic manganese metal powder ((HPEMP), also known as Mn metal), on human thyroid peroxidase (TPO) in vitro.
A single valid TPO-catalyzed iodination experiment using human thyroid microsomes (HTM) tested both materials at eight concentrations in triplicate.
Solubility testing indicated that MnCl₂ was fully soluble at relevant concentrations, whereas Mn metal showed very low water solubility.
Overall, MnCl₂ did not inhibit human TPO-catalyzed iodination up to 100 µM, and due to the very low water solubility of Mn metal and the lower actual Mn exposure, Mn metal can also be considered negative in the TPO assay up to 100 µM. As MnCl2 did not inhibit the human TPO-catalyzed iodination up to a concentration of 100 µM, it can be considered that Mn metal will be negative in the TPO assay up to a concentration of
100 µM as well.