Effect of Chronic Exposure to Pesticide Methomyl on Antioxidant Defense System in Testis of Tilapia (Oreochromis niloticus) and Its Recovery Pattern

Shunlong Meng,Jiazhang Chen,Pao Xu,Chao Song,Yao Zheng,Limin Fan,Xi Chen,Liping Qiu

doi:10.3390/app11083332

Shunlong Meng, Jiazhang Chen + Show 6 more

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https://doi.org/10.3390/app11083332

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Abstract

The chronic effect of environmental methomyl on the antioxidant system in testis of Nile tilapia (Oreochromis niloticus) and its recovery pattern was investigated. Tilapia were exposed to sublethal concentrations of 0.2, 2, 20 and 200 μgL−1 methomyl for 30 days and thereafter moved to methomyl-free water for 18 days. Antioxidant levels in testis, including glutathione peroxidase, catalase, glutathione-S-transferase, glutathione reductase, superoxide dismutase, reduced glutathione, oxidized glutathione were measured every 6 days during the period of exposure, and at 18 days after being transferred to methomyl-free water. The results showed that lower methomyl concentration (0.2 μgL−1) had no effect on the above antioxidants, thus 0.2 μgL−1 could be seen as NOAEL for methomyl to tilapia. However, higher methomyl concentration of 2, 20 and 200 μgL−1 could significantly influence the above antioxidants. Glutathione peroxidase and oxidized glutathione increased significantly. On the contrary, reduced glutathione decreased significantly. Catalase, superoxide dismutase, glutathione reductase, glutathione-S-transferase increased at lower methomyl (2 and 20 μgL−1), but decreased at higher methomyl (200 μgL−1). The recovery test showed that oxidative damage caused by lower methomyl of 2 and 20 μgL−1 was reversible, and oxidative damage caused by higher methomyl of 200 μgL−1 was irreversible within 18 days of recovery period.

Highlights

Methomyl (C5H10N2O2S) is a carbamate pesticide yet is widely used and has greatly contributed to pest control and promoted the harvest of agricultural products
The results of effect of chronic exposure to pesticide methomyl on antioxidant defense system in testis of tilapia (Oreochromis niloticus) and recovery pattern were showed in Figure 1 and Table S1
No significant changes (p > 0.05) were observed in the antioxidant enzyme activities and contents in testis of tilapia exposed to 0.2 μg L−1 methomyl, whereas the testis of fish exposed to concentrations of 2, 20 or 200 μg L−1 showed significant changes (p < 0.05): glutathione peroxidase (GPx) and GSSG significantly increased, and GSH significantly decreased (p < 0.05)

Summary

Introduction

Methomyl (C5H10N2O2S) is a carbamate pesticide yet is widely used and has greatly contributed to pest control and promoted the harvest of agricultural products. Aerobic organisms have evolved mechanisms to activate antioxidant defense systems in various organs and tissues; these involve antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), as well as antioxidant scavengers (e.g., glutathione), to protect from damage caused by high levels of ROS [4]. ROS can be eliminated by antioxidant defenses during normal physiological processes; severe oxidative stress will suppress the activities of antioxidant enzymes and lead to oxidative damage [8]. The antioxidant enzymes GPx, CAT, GST, SOD and GR, and the non-enzymatic antioxidants reduced glutathione (GSH) and oxidized glutathione (GSSG), are often used as biomarkers for early detection of harmful effects as well as chronic damage caused by exposure to toxic substances [10]

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