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

Abstract

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 (EE 2 )/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 (E 2 ) 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 E 2 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 E 2 . In female fish, it is most likely that endogenous levels of E 2 diminished the alterations elicited by EE 2 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.Palabras clave: gonadotropinas, estradiol, vitelogenina, metalotioneínas, respuesta ligada al sexo RESUMENGirardinichthys viviparus es un pez mexicano endémico y en peligro de extinción con viviparidad matrotrófica que sólo habita en algunos cuerpos de agua contaminados del Valle de México. En este estudio, especimenes de G. viviparus de ambos sexos fueron expuestos durante 21 días a una mezcla de metales a concentraciones ambientalmente relevantes (T1) y a la misma mezcla enriquecida con 25 ng de 17α-etinil estradiol (EE 2 )/L (T2). En la cabeza y las gónadas se midieron biomarcadores implicados en el eje endocrino sexual hipotálamo-pituitaria-gónadas-hígado, así como las concentraciones de estradiol (E 2 ), gonadotropina I y II (GtH I y GtH II, respectivamente). En el Rev. Int. Contam. Ambie. 33 (2) 289-302, 2017 DOI: 10.20937/RICA.2017 H.F. Olivares-Rubio et al. 290hígado y las gónadas se evaluó la vitelogenina (VTG) y en la cabeza, el hígado y las gónadas los niveles de metalotioneínas (MT). En la cabeza y las gónadas de los peces expuestos a ambos tratamientos se observaron aumentos de la GtH I, disminuciones de GtH II y alteraciones de E 2 . Solamente en los peces expuestos al T2 se encontraron incrementos hepáticos y gonadales de VTG. Las MT fueron inducidas particularmente por el T2. Sin embargo, se observó una reducción dependiente del tiempo. En ambos tratamientos, el punto de control hipotálamo-pituitaria fue el más afectado y sus alteraciones fueron evidenciadas por los contenidos de E 2 . En contraste con los machos, en hembras es probable que los niveles e...

Effect of heavy metals in fish reproduction: A review

“…In rainbow trout juveniles, Cd @ 0.05 mg l or more may raise the levels of estradiol (E2) while both E2 and testosterone -1 (T) were reduced in medaka (Orizias latipes) subjected to 10 g l Cd (Garriz et al, 2018). The brain and gonads of Girardinichthys viviparous subjected to relevant environmental quantities of a mixture of metals showed an increase in FSH, a decrease in LH, and changes in E2 levels (Olivares-Rubio et al, 2017). Cd ketotestosterone (11-KT), with 11-KT being more effective than T. (Kim et al, 2014).…”

“…Metal exposure may cause the body to expend more energy to maintain normal metabolism, resulting in a faster metabolic pace along with a lesser amount of Furthermore, Cd was observed to disturb calcium homeostasis in the pituitary gland and gonads, causing hormone output to be disrupted. Exposure to a mixture of metals in the environment (Cu, Fe, Mn, Pb, Zn) leads to changes in gonadotropins and E2 profiles in Girardinichthys (Olivares-Rubio et al, 2017). Enzymes concerned in gonadal steroidogenesis and hepatic steroid metabolism may be directly inhibited by Cd.…”