Influence of Organotin on Thyroid Morphophysiological Status

Abstract

Tributyltin is an environmental contaminant found in antifouling paints, widely used in ships and other vessels. TBT causes endocrine-disrupting effects in mammals, due to its possible transfer through marine food chains, and the consequent consumption of contaminated seafood. Thus, we aimed to evaluate whether the treatment with TBT could induce histophysiological changes in the thyroid gland. TBT promoted disorganization of parenchyma, fibrosis and vascular congestion in the gland. Moreover, morphometric analysis showed statistically significant changes in the follicle of rats treated with TBT, with increased colloid and epithelial area, besides increased epithelial/colloid area relation, but no statistical differences were found in epithelial height. Nevertheless, collagen deposition was seen in the thyroids of treated groups. In thyroid physiological status, we did not observe intergroup significant changes in plasma levels of total T 3 and T 4 after treatment, even though we have found a time-dependent increase of T 4 levels in TBT-treated groups. We also detected an increased H2O2 production in the thyroid of TBT-treated group, besides increased dual oxidase protein levels, the main enzyme involved in hydrogen peroxide production. Since H2O2 is a reactive oxygen species, TBT could induce oxidative stress, what could be involved in the morphophysiological changes observed in the gland. These data provided the evidence that exposure to TBT induces morphophysiological changes in the thyroid gland, and may therefore correspond to a potential risk factor for thyroid disorders.

Disruptive Effect of Organotin on Thyroid Gland Function Might Contribute to Hypothyroidism

“…Moreover, they demonstrated that TBTCl might inhibit TR expression in human HepG2 cells, both by direct action and by corepressor/coactivator inhibition/increase, such as nuclear receptor corepressor (NCoR) and steroid receptor coactivator (SRC-1), respectively. In contrast, Rodrigues-Pereira et al [40] verified TBT action on male Wistar rats and found that T4 levels were increased; this finding may be associated with type 2 deiodinase (D2) activity inhibition by TBT. The deiodinases, D1, D2, and D3, are responsible for the deiodination of T3 and T4 [46, 47].…”

“…Rodrigues-Pereira et al [40] verified TBT action on male Wistar rats that were treated orally with 500 ng/kg or 1000 ng/kg of TBT per day for 15 days. The authors found that animals treated with a larger dose of TBT showed apparent reduction in the follicle, colloid, and epithelium areas of the thyroid with a higher deposition of collagen.…”

“…The authors found that animals treated with a larger dose of TBT showed apparent reduction in the follicle, colloid, and epithelium areas of the thyroid with a higher deposition of collagen. These structures may contribute to a loss of thyroid parenchyma organization [40]. In another recent study, male rats received a dose of 5 mg/kg TBT (5 × 10 6 ng/kg) orally for 30 days.…”

“…The deiodinases, D1, D2, and D3, are responsible for the deiodination of T3 and T4 [46, 47]. The intracellular and plasma levels of TH are regulated by deiodinases, so a repression of D2 activity may lead to increased plasma T4 levels [40].…”