title: Effects of the insecticide fipronil on reproductive endocrinology in the fathead minnow.
abstract: Gamma-aminobutyric acid (GABA) and GABA receptors play an important role in neuroendocrine regulation in fish. Disruption of the GABAergic system by environmental contaminants could interfere with normal regulation of the hypothalamic-pituitary-gonadal axis, leading to impaired fish reproduction. The present study used a 21-d fathead minnow (Pimephales promelas) reproduction assay to investigate the reproductive toxicity of fipronil (FIP), a broad-spectrum phenylpyrazole insecticide that acts as a noncompetitive blocker of GABA receptor-gated chloride channels. Continuous exposure up to 5 µg FIP/L had no significant effect on most of the endpoints measured, including fecundity, secondary sexual characteristics, plasma steroid and vitellogenin concentrations, ex vivo steroid production, and targeted gene expression in gonads or brain. The gonad mass, gonadosomatic index, and histological stage of the gonad were all significantly different in females exposed to 0.5 µg FIP/L compared with those exposed to 5.0 µg FIP/L; however, there were no other significant effects on these measurements in the controls or any of the other treatments in either males and females. Overall, the results do not support a hypothesized adverse outcome pathway linking FIP antagonism of the GABA receptor(s) to reproductive impairment in fish.
authors.affiliation: Ecological Exposure Research Division, National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency, Cincinnati, Ohio, USA. bencic.david@epa.gov
authors.forename: David C
authors.initials: DC
authors.lastname: Bencic
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Villeneuve
authors.forename: Adam D
authors.initials: AD
authors.lastname: Biales
authors.forename: Lindsey
authors.initials: L
authors.lastname: Blake
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Durhan
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Jensen
authors.forename: Michael D
authors.initials: MD
authors.lastname: Kahl
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Makynen
authors.forename: Dalma
authors.initials: D
authors.lastname: Martinović-Weigelt
authors.forename: Gerald T
authors.initials: GT
authors.lastname: Ankley
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods; D003530:Cyprinidae / Q000502:physiology*; D004703:Endocrine System / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005298:Fertility; D006066:Gonads / Q000502:physiology; D007306:Insecticides / Q000633:toxicity*; D008297:Male; D011720:Pyrazoles / Q000633:toxicity*; D012098:Reproduction / Q000187:drug effects / Q000502:physiology; D014819:Vitellogenins / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000633:toxicity; D005680:gamma-Aminobutyric Acid / Q000502:physiology
chemical_list: D007306:Insecticides; D011720:Pyrazoles; D014819:Vitellogenins; D014874:Water Pollutants, Chemical; D005680:gamma-Aminobutyric Acid; C082360:fipronil
keywords: Endocrine disruption; Fecundity; Fish; Neurotransmitter; Pesticide