Toxicity of Aqueous L-Selenomethionine and Tert-Butyl Hydroperoxide Exposure to Zebrafish (Danio rerio) Embryos Following Tert-Butyl Hydroquinone Treatment.

Allyson K Gerhart,David M Janz

doi:10.3390/toxics7030044

Abstract

Aqueous L-selenomethionine (SeMet) embryo exposures represent a rapid and simplified method for investigating the embryotoxic effects of SeMet. Using zebrafish (Danio rerio) as a model organism, the objective of the present study was to characterize the effects of waterborne exposure to both SeMet and tert-butyl hydroperoxide (tBOOH) to early life stages of zebrafish pre-treated with the antioxidant tert-butyl hydroquinone (tBHQ) in an attempt to investigate the mechanism of Se toxicity as it relates to oxidative stress. During the initial concentration range finding experiment, recently fertilized embryos were exposed for five days to 5, 25, 125, and 625 µg Se/L (as SeMet). These exposures informed the second experiment in which embryos were exposed to two concentrations of SeMet (25 and 125 µg Se/L) and 75 mg/L tBOOH either with (tBOOH-t, 25-t, 125-t) or without (tBOOH, 25, 125) a 4 h 100 µg/L tBHQ pre-treatment. Survival, hatchability, time to hatch, the frequency and severity of deformities (total and type), and changes in the expression of seven antioxidant-associated genes were determined. Exposures to SeMet and tBOOH reduced hatchability, increased time to hatch, decreased survival, increased the incidence and severity of deformities, and increased glutathione-disulfide reductase (gsr) expression in the pre-treated tBOOH treatment group.

Highlights

The zebrafish (Danio rerio) represents one of the most widely-used small fish models in toxicological research, due to beneficial traits such as a short life cycle, frequent egg production, ease of culture, and a transparent embryo chorion which allows for the determination of fertilization status and morphological analysis throughout development [1]
Animal care and all experimentation were conducted in compliance with the University Committee on Animal Care and Supply (UCACS) and was approved by the Animal Research Ethics Board (AREB)
No differences were observed between embryos pre-treated with tert-butyl hydroquinone (tBHQ) and embryos exposed to either SeMet or tBOOH alone for all endpoints evaluated in the present study

Summary

Introduction

The zebrafish (Danio rerio) represents one of the most widely-used small fish models in toxicological research, due to beneficial traits such as a short life cycle, frequent egg production, ease of culture, and a transparent embryo chorion which allows for the determination of fertilization status and morphological analysis throughout development [1]. Exposure to elevated concentrations of selenomethionine (SeMet), the predominant form of Se in the diet, during the sensitive, early life stages often results in an increased incidence of edema and mortality, as well as teratogenic effects such as spinal/skeletal deformities, misshapen or missing fins, and craniofacial malformations in developing fish larvae [3,4].

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