The differences in bioaccumulation and effects between Se(IV) and Se(VI) in the topmouth gudgeon Pseudorasbora parva

Shanshan Ma,Lingtian Xie,Shicong Geng,Liang Yan,Xiangfeng Zeng,Qianru Zhang,Yongju Luo,Hongxing Chen

doi:10.1038/s41598-018-32270-z

Abstract

Selenium (Se) might be protective against oxidative stress at nutritional levels, but elevated Se concentrations in the diet has been revealed as the main culprit for the extinction of natural fish populations in Se-contaminated lakes. Though Se predominate as waterborne selenite (IV) and selenate (VI) in the water, the differences in bioaccumulation, effects (e.g., oxidative stress, antioxidants etc.) and molecular mechanisms between Se(IV) and Se(VI) have been relatively understudied in wild fish. In this study, the P. parva were exposed to waterborne Se (10, 200 and 1000 μg/L of Se(IV) or Se(VI)) and sampled at 4, 14 and 28 days. Bioaccumulation, tissue distributions of Se and following effects in different tissues were evaluated. The results showed that the levels of Se in the gills and intestine were significantly elevated with a seemingly concentration-dependent pattern in the Se(IV) treatment, with respectively 173.3% and 57.2% increase after 28 days of exposure, relative to that of Se(VI) treatment. Additionally, significant accumulation of Se was also observed in the muscle of Se(IV) treated fish. Se exposure increased the MDA levels in the brain and gills in the Se(IV) treatment, but less apparent in the Se(VI) treatment. Meanwhile, Se exposure lowered (at least 56%) the activity of GST in the gills, but increased the activity of AChE in the muscle (~69%) and brain (~50%) after 28 d. Most importantly, after 28 d of exposure, Se exposure caused significant decrease in GSH levels in the gills (at least 35%) and in all tissues examined at the highest test concentration. In general, the results showed that Se(IV) led to faster accumulation of Se than Se(VI) in P. parva, and the resulted lipid peroxidation was closely related to the levels of antioxidants, especially GSH. Our results suggest that the ecotoxicological effects of waterborne selenite and selenate differ in this freshwater species in the field.

Highlights

Aquatic organisms including fish can take up Se via waterborne and dietary routes[6,7]
It has been suggested that selenium-mediated thiol oxidation cause reactive oxygen species (ROS) and oxidative stress can be a factor related to selenium-induced toxicity[12,13]
Tissues burdens of total Se in P. parva exposed to Se(IV) were higher than those of P. parva exposed to Se(VI) (p < 0.05)

Summary

Introduction

Aquatic organisms including fish can take up Se via waterborne and dietary routes[6,7]. Glutathione (GSH) is the most plentiful intracellular thiol-based antioxidant, and function as a sulfhydryl buffer It has the function of detoxifying compounds via conjugation reactions catalyzed by glutathione S-transferases (GST). Due to Se(IV) and Se(VI) are the main forms of Se and possibly the predominant Se species confronted in waterborne exposures by organisms in the aquatic ecosystems, the study on the bioaccumulation of aqueous inorganic Se in fish is relatively scarce. The topmouth gudgeon Pseudorasbora parva is a small-sized freshwater cyprinid, originating from Northeastern regions of China It has many attractive biological traits ideal for the ecotoxicological studies, including early maturity (sexually mature at 1 year), batch spawning, nest guarding and broad environmental tolerance limits[20]. The physiological effects of Se on the brain, gills, intestine and muscle were determined

Results

Discussion

Conclusion