title: Effects of the feedlot contaminant 17alpha-trenbolone on reproductive endocrinology of the fathead minnow.
abstract: Trenbolone acetate is a growth promoter widely used for beef production in the U.S. Two biologically active metabolites of the acetate, 17beta- and 17alpha-trenbolone, are ligands of vertebrate androgen receptors and comparatively stable in the waste of treated animals. Both have been detected in surface water associated with beef feedlots, suggesting a potential risk to aquatic animals. In previous work we evaluated the effects of beta-trenbolone on reproductive endocrinology of the fathead minnow (Pimephales promelas) in a 21-day test. The purpose of the present study was to conduct a similar set of experiments with alpha-trenbolone which, based on binding to mammalian androgen receptors, was expected to be less potent than beta-trenbolone. Fecundity of the fish was significantly reduced by alpha-trenbolone with an EC50 (95% confidence interval) of 0.011 (0.007-0.016) microg/L. In females, alpha-trenbolone reduced plasma vitellogenin and steroid concentrations and also induced the production of dorsal nuptial tubercles, structures normally present only in spawning males. Overall, effects of alpha-trenbolone on the reproductive system of the fish were qualitatively and quantitatively quite similar to those caused by beta-trenbolone. Part of this similarity might arise from the fact that a substantial amount of the alpha-trenbolone appeared to be converted to beta-trenbolone by the fish. Tissue concentrations of the beta-isomer were consistently similar to or greater than concentrations of alpha-trenbolone, despite the fact that no beta-trenbolone was detected in the exposure water. The present study demonstrates the importance of considering both alpha- and beta-trenbolone in assessing the potential ecological risk of androgens associated with beef feedlot discharges.
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Boulevard, Duluth, Minnesota 55804, USA. jensen.kathleen@epa.gov
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Jensen
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Makynen
authors.forename: Michael D
authors.initials: MD
authors.lastname: Kahl
authors.forename: Gerald T
authors.initials: GT
authors.lastname: Ankley
mesh_terms: D000818:Animals; D003530:Cyprinidae; D005260:Female; D008297:Male; D011944:Receptors, Androgen / Q000378:metabolism; D012727:Sex Characteristics; D046468:Sexual Development; D013256:Steroids / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution; D014204:Trenbolone Acetate / Q000032:analysis*; D014819:Vitellogenins / Q000378:metabolism; D014867:Water / Q000032:analysis; D014874:Water Pollutants, Chemical
chemical_list: D011944:Receptors, Androgen; D013256:Steroids; D014819:Vitellogenins; D014874:Water Pollutants, Chemical; D014867:Water; D014204:Trenbolone Acetate