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.