Effect of thimerosal on thyroid hormones metabolism in rats

Abstract

Mercury seems to exert an inhibitory effect on deiodinases, but there are few studies using Thimerosal (TM) as the mercury source. We aimed to elucidate the effect of TM on thyroid hormones peripheral metabolism. Adult Wistar female rats received 0.25 µg or 250 µg TM/100 g BW, IM, twice a week, for a month. We evaluated serum total T3 and T4, D1 activity using 125I-rT3 as tracer, and D2 activity using 125I-T4. NADPH oxidase activity was measured by Amplex-red/HRP method and mRNA levels by real time PCR. Serum T4 was increased and T3 decreased by the greatest dose of TM. Even though D1 activity in pituitary and kidney was reduced by the highest dose of TM, hepatic D1 activity and D1 mRNA levels remained unchanged. D2 activity was also significantly decreased by the highest dose of TM in all CNS samples tested, except cerebellum, but D2 mRNA was unaltered. mRNA levels of the tested NADPH oxidases were not affected by TM and NADPH oxidase activity was either unaltered or decreased. Our results indicate that TM might directly interact with deiodinases, inhibiting their activity probably by binding to their selenium catalytic site, without changes in enzyme expression.

A study on the potential reprotoxic effects of thimerosal in male albino rats

“…Mercury affects the function of the endocrine system by decreasing its hormone-receptor binding ability ( Iavicoli et al, 2009 ). Previous studies have reported that thimerosal critically affected the metabolism of thyroid hormones in rats by reducing the activity of deiodinase D1 and D2 in tissues by binding directly to the selenium of catalytic site ( Pantaleao et al, 2017 ). It has been experimentally proved that mercury causes damage to male gonads and disrupts steroidogenesis and spermatogenesis ( Zhu et al, 2000 ).…”