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Direct Effects, Compensation, and Recovery in Female Fathead Minnows Exposed to a Model Aromatase Inhibitor
Abstract
Background
Several chemicals in the environment have the potential to inhibit aromatase, an enzyme critical to estrogen synthesis.Objectives
The objective of this study was to provide a detailed characterization of molecular and biochemical responses of female fathead minnows to a model aromatase inhibitor, fadrozole (FAD).Methods
Fish were exposed via water to 0, 3, or 30 microg FAD/L for 8 days and then held in clean water for 8 days, with samples collected at four time points during each 8-day period. We quantified ex vivo steroid production, plasma steroids, and plasma vitellogenin (Vtg) concentrations and analyzed relative transcript abundance of 10 key regulatory genes in ovaries and 3 in pituitary tissue by real-time polymerase chain reaction.Results
Ex vivo 17beta-estradiol (E2) production and plasma E2 and Vtg concentrations were significantly reduced after a single day of exposure to 3 microg or 30 microg FAD/L. However, plasma E2 concentrations recovered by the eighth day of exposure in the 3-microg/L group and within 1 day of cessation of exposure in the 30-microg/L group, indicating concentration- and time-dependent physiologic compensation and recovery. Concentration-dependent increases in transcripts coding for aromatase (A isoform), cytochrome P450 side-chain cleavage, steroidogenic acute regulatory protein, and follicle-stimulating hormone receptor all coincided with increased E2 production and recovery of plasma E2 concentrations.Conclusions
Results of this research highlight the need to consider compensation/adaptation and recovery when developing and interpreting short-term bioassays or biomarkers or when trying to predict the effects of chemical exposures based on mode of action.Many UC-authored scholarly publications are freely available on this site because of the UC's open access policies. Let us know how this access is important for you.