Disruption of hypothalamus-pituitary-liver-gonads axis in the endangered Girardinichthys viviparus exposed to environmentally relevant concentrations of a mixture of metals and with 17α-ethynil estradiol

Girardinichthys viviparus is an endemic and endangered Mexican fish species with matrotrophic viviparity that only inhabits in some polluted water bodies in the Valley of Mexico. In the current study, G. viviparus of both sexes were exposed for 21 days to a mixture of metals with relevant environmental concentrations (T1) and to the same mixture spiked with 25 ng of 17α-ethynil estradiol (EE₂)/L (T2). Some biomarkers involved in endocrine disruption of the hypothalamus-pituitary-liver-gonads axis such as gonadotropins I and II (GtH I and GtH II, respectively), and estradiol (E₂) concentrations in the head and gonads were measured. Vitellogenin (VTG) in the liver and gonads, and metallothionein (MT) in the head, liver and gonads were assessed. Increases of GtH I and decreases in GtH II, and alterations of E₂ in the head and gonads were found in fish treated with T1 and T2. Higher content of hepatic and gonadal VTG only in fish treated with T2 was detected. MT was notably induced by T2; however, a time-dependent MT reduction was observed. In both treatments, the hypothalamic-pituitary control point was most affected and their alterations were documented by gonadal and head content of E₂. In female fish, it is most likely that endogenous levels of E₂ diminished the alterations elicited by EE₂ on this control point of the axis in contrast with male fish. The endocrine disruption of this fish species is a dynamic and complex process.