Influence of dietary iodine on drug-induced hypothyrodism in the rat

A biophysical probe on the binding of 2-mercaptothioazoline to bovine hemoglobin

2-Mercaptothiazoline (MTZ) is broadly present in daily use as an antifungal reagent, a brightening agent, and a corrosion inhibitor. MTZ is potentially harmful for human health. Although the toxic effects of MTZ on experimental animals have been reported, the effects of MTZ on the proteins in the circulatory system at the molecular level have not been identified previously. Here, we explored the interaction of MTZ with bovine hemoglobin (BHb) in vitro using multiple spectroscopic techniques and molecular docking. In this study, the binding capacity, acting force, binding sites, molecular docking simulation, and conformational changes were investigated. MTZ quenched the intrinsic emission of BHb via the static quenching process and could spontaneously bind with BHb mainly through van der Waals forces and hydrogen bond. The computational docking visualized that MTZ bound to the β2 subunit of BHb, which further led to some changes of the skeleton and secondary structure of BHb. This research provides valuable information about the molecular mechanisms on BHb induced by MTZ and is beneficial for clarifying the toxicological actions of MTZ in blood.

Antithyroid action of tamoxifen in the rat: in vivo and in vitro studies

The influence of administration of tamoxifen (TAM) on thyroid metabolism was investigated. The potential action of TAM on iodine in the thyroid gland was evaluated by determination of the equilibrium constant of the charge transfer complex formed with molecular iodine and by computational studies. Adverse effects of TAM on thyroid function parameters were also investigated in female Wistar rats. Rats were treated for seven weeks with 5 mg/kg/day of TAM. Irrespective of the iodine content of the diet, administration of TAM led to goitre and a significant increase in levels of T4 and TSH. Similar results, albeit more marked, were observed after administration of an inhibitor of thyroid peroxidase. We also showed that TAM forms charge transfer complex with iodine (Kc = 876 liters/mol). We concluded that under our experimental conditions, TAM exerts antithyroid activity from an action on thyroid peroxidase. Nevertheless, when the exogenous iodine contribution is restricted, TAM may sequester iodine in the form of charge transfer complexes, thereby enhancing hypothyroidism.