Endocrine Disturbances And Neurobehavioral Toxicity Of Gestodene (GES) On HPT Axis In Two Teleost

With the advancement of medicine and social needs,the more progestins have been introduced into the global market and are widely used in medicine and clinical therapy.In addition,progestins are used to livestock industry for promoting livestock growth and fattening.Subsequently,progestins will entre in aquatic environment with the excreta(feces and urine)of livestock and humans,domestic sewage and pharmaceutical industry wastewater.And they are frequently detected in aquatic environments at the concentrations ranging from ng/L to ?g/L.Increasing number of studies various adverse effects of progestins in aquatic animals at low concentration.However,most studies have focused on reproductive toxicity,such as affecting reproduction,sex differentiation,gonadal tissue damage,sex behavior.Only limited data are available on the effect of thyroid endocrine system and neurobehavioral.Therefore,this study focused on the endocrine disrupting and neurobehavioral effects of GES on the HPT axis in teleost fish(Danio rerio)and mosquito fish(Gambusia affinis)at different developmental stages(early life and adult stages).The main results from this study are given as follows:1.The first experiment aimed to provide the effects of binary mixtures of GES and 17?-ethinylestradiol(EE2)(41-5239ng/L)in zebrafish early life stages.The effects of GES and EE2 alone or their mixture exposure on development,locomotor behavior and transcriptional expression of the genes on the HPT axis were assessed in zebrafish eleuthero-embryos.The results showed that the total mortality rate and malformation rate were generally under 10%,and no acute embryo toxic effects.GES and EE2 significantly inhibited the growth and development of zebrafish embryos.In addition,the level of T3 was significantly increased,while T4 was inhibited.The results of locomotor activity of the larval zebrafish showed that the total distance and velocity of zebrafish larvae were reduced after GES and EE2 exposure.And the ACh E activity after mixture exposure was generally higher than that of single exposure.To sum up,the interactive effects of GES and EE2 on the developmental toxicity and neurotoxicity were synergistic.With respect to the transcriptional regulation on HPT axis,there was no clear pattern in the change of the transcripts of these genes over time and with concentrations at 48 and 96 hpf,and their mixtures showed interactive effects in embryonic zebrafish.Interestingly,the significant expression of Trh was overlapped among all treatment group,which indicated high sensitivity of Trh gene responded to these chemical.GES and EE2 elicit different transcription on HPT system and their mixtures show significant interaction in embryonic zebrafish.In other words,the aquatic environment where GES and EE2 coexist will pose a greater risk to the growth and development of fish during the early life stages mediated by HPT axis.2.The second experiment aimed to investigate the effects of GES(4-379 ng/L)on thyroid endocrine system and neurobehavioral in adult Western mosquitofish after 60 d.The results showed that the body length,bodyweight and locomotor behavior of female mosquitofish were significantly inhibited.Compared with the control,the levels of T3 was significantly increased in a dose-dependent manner in all treatment groups,while T4 was slightly decreased.The activity of ACh E decreased significantly in the low and medium concentration groups(4.42ng/L and 40.78 ng/L),while increased significantly at 378.67 ng/L.The results of histopathological sections showed that thyroid follicles and cerebellum were damaged with a dose-response relationship(such as decreased or missing glia in thyroid follicles,hyperplasia of follicular epithelial cells,vacuolization of cerebellar tissue,thrombosis,increased proportion of apoptosis)).With respect to the transcriptional regulation on HPT axis and neurodevelopment,the results of the transcription levels of genes related to HPT axis and neurodevelopment showed that the transcription level of Bdnf was significantly up-regulated after GES exposure at 40.78 ng/L and 378.67 ng/L.The transcripts of Trh and Dio2 showed significant changes after GES exposure at 40.78 ng/L and 378.67 ng/L.In summary,GES could significantly affect the mosquitofish at transcription,neurobehavioral and histology levels,and had potential risk for the aquatic organisms.