Abstract
The normal dose of 17α-methyltestosterone (MT) used in fish farming was 60 mg/L, and now the analysis of residual androgens was carried out in waste water obtained from the Beijing area, which could be detected in levels ranging from 4.1 to 7.0 ng/L. For the purpose of aquatic early warning, the present study clearly demonstrated that chronic exposure by higher concentration of MT than environmental relevant concentrations could trigger oxidative stress response to juvenile tilapia by modulating hepatic antioxidant enzyme activities and gene transcription. Some antioxidative parameters (T-GSH, GSH/GSSG and MDA) were significant decreased under 0.5 mg/L MT exposure at 7 and 14 days. Some antioxidant enzymes (SOD, CAT and GST) and transcriptional changes (sod and cat) were revealed significant decreases for MT treated groups at 7 days. Total antioxidant capacity was significant increased only in 5 mg/L MT exposure groups, but GR activities were not affected all through the whole exposure period. Almost all of the antioxidant enzymatic genes detected in the present study were showed significant increments for MT exposure both at 14 and 21 days, and the genotoxicity profile of antioxidant enzymatic genes were revealed dose-dependent manner. This study presented evidence that MT could result in oxidative stress response in the early stages of GIFT tilapia.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-1946-6) contains supplementary material, which is available to authorized users.
Highlights
The normal dose of 17α-methyltestosterone (MT) used in fish farming was 60 mg/L, and the analysis of residual androgens was carried out in waste water obtained from the Beijing area, which could be detected in levels ranging from 4.1 to 7.0 ng/L
Androgenic analogues used as oxidative stress inducers to produce excess reactive oxygen species (ROS), which resulted in hepatotoxicity
Except for sod and gpx1 transcripts at 14 days (Fig. 3A, C), all of the antioxidant enzymatic genes detected in the present study showed significant increments for MT exposure both at 14 and 21 days, and the genotoxicity profile of antioxidant enzymatic genes revealed dose-dependent manner. gr and gpx1 transcripts were not affected at 7 days (Fig. 3C, D)
Summary
The normal dose of 17α-methyltestosterone (MT) used in fish farming was 60 mg/L, and the analysis of residual androgens was carried out in waste water obtained from the Beijing area, which could be detected in levels ranging from 4.1 to 7.0 ng/L. For the purpose of aquatic early warning, the present study clearly demonstrated that chronic exposure by higher concentration of MT than environmental relevant concentrations could trigger oxidative stress response to juvenile tilapia by modulating hepatic antioxidant enzyme activities and gene transcription. Almost all of the antioxidant enzymatic genes detected in the present study were showed significant increments for MT exposure both at 14 and 21 days, and the genotoxicity profile of antioxidant enzymatic genes were revealed dose-dependent manner. Our previous study showed that hepatic SOD, CAT and GPx activities and their transcripts were increased in Nile tilapia under methomyl exposure (Meng et al 2014a, b). We know MT has the potential to induce oxidative stress, the main purpose of the present study was to investigate the hepatic genotoxicity (transcriptional) and antioxidant enzymatic signature (post transcriptional) of freshwater GIFT tilapia O. niloticus juveniles responding to 0.5, 5 mg/L MT exposure. The present study will detect other antioxidant parameters to further testify that hepatic antioxidant defense system was impaired following MT exposure
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