Tributyltin chloride (TBT) – a chemical used in antifouling paints, and a known endocrine-disrupting chemical (EDC) – disrupts the hypothalamus-pituitary-adrenal (HPA) axis in female rats, according to a study recently published in Endocrinology.
Researchers led by Professor Jones B. Graceli, of Universidade Federal do Espírito Santo, in Vitória, ES, Brazil, point out that TBT has been shown to have endocrine-disrupting effects. “TBT exposure can lead to alterations in neural, reproductive, immune, and metabolic functions in both in vivo and in vitro models, suppressing immune responses and increasing adiposity,” the authors write. Humans are mainly exposed to TBT through eating seafood, since the chemical tends to accumulate in fish.
The researchers also write that “[s]tudies have supported the key roles of inflammatory mediators and obesity in the abnormal HPA axis function,” but that the studies examining the effects of TBT on the HPA axis – one of the most important neuroendocrine axes, since it plays a key role in stress processes – are rare.
The team exposed female rats to TBT and examined its effects on their HPA axes. They detected high corticosterone levels, high corticotropin-releasing hormone (CRH) expression and low adrenocorticotropic hormone (ACTH) expression. “In addition,” the authors write, “TBT leads to an increased in the inducible nitric oxide synthase protein expression in the hypothalamus of TBT rats. Morphophysiological abnormalities, including increases in inflammation, a disrupted cellular redox balance, apoptosis, and collagen deposition in the pituitary and adrenal glands, were observed in TBT rats.
The researchers conclude that their data show that TBT leads to functional dissociation between CRH, ACTH, and costicosterone, “which could be associated an inflammation and increased of inducible nitric oxide synthase expression in hypothalamus. Thus, TBT exerts toxic effects at different levels on the HPA axis function.”
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