Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8651
Title: Wastewater treatment plant effluent alters pituitary gland gonadotropin mRNA levels in juvenile coho salmon (Oncorhynchus kisutch)
Author: Louisa B. Harding, Irvin R. Schultz, Denis A.M. da Silva, G. M. Ylitalo, Dave Ragsdale, Stephanie I. Harris, Stephanie Bailey, Barry V. Pepich, Penny Swanson
Publication Year: In press
Journal: Aquatic Toxicology
Keywords: coho salmon,water quality,endocrine disruption,gonadotropins

It is well known that endocrine disrupting compounds (EDCs) present in wastewater treatment plant (WWTP) effluents interfere with reproduction in fish, including altered gonad development and induction of vitellogenin (Vtg), a female-specific egg yolk protein precursor produced in the liver. As a result, studies have focused on the effects of EDC exposure on the gonad and liver. However, impacts of environmental EDC exposure at higher levels of the hypothalamic-pituitary-gonad (HPG) axis are less well understood. The pituitary gonadotropins (Gths), follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh) are involved in all aspects of gonad development and are subject to feedback from gonadal steroids making them a likely target of endocrine disruption. In this study, the effects of WWTP effluent exposure on pituitary gonadotropin (Gth) mRNA expression were investigated in juvenile coho salmon (Oncorhynchus kisutch). First, a controlled 72-hour exposure to 17α-ethynylestradiol (EE2) and trenbolone (TREN) was performed to evaluate the response of juvenile coho salmon to EDC exposure. Second, juvenile coho salmon were exposed to 0, 20 or 100% effluent from eight WWTPs from the Puget Sound, WA region for 72 hours. Juvenile coho salmon exposed to 2 and 10 ng EE2 L-1 had 17-fold and 215-fold higher Lh beta-subunit (lhb) mRNA levels relative to control fish. Hepatic vtg mRNA levels were dramatically increased 6,670-fold, but only in response to 10 ng EE2 L-1 and Fsh beta-subunit (fshb) mRNA levels were not altered by any of the treatments. In the WWTP effluent exposures, lhb mRNA levels were significantly elevated in fish exposed to five of the WWTP effluents. In contrast, transcript levels of vtg were not affected by any of the WWTP effluent exposures. Mean levels of natural and synthetic estrogens in fish bile were consistent with pituitary lhb expression, suggesting that the observed lhb induction may be due to estrogenic activity of the WWTP effluents. These results suggest that lhb gene expression may be a sensitive index of acute exposure to estrogenic chemicals in juvenile coho salmon. Further work is needed to determine the kinetics and specificity of lhb induction to evaluate its utility as a potential indicator of estrogen exposure in immature fish. 

Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Assess the impacts of toxic chemicals and other pollutants across biological scales, and identify pollution reduction strategies that improve habitat quality.