Toxic Effects of Copper Sulfate and Trichlorfon on the Intestines of Zebrafish (Danio rerio)

Abstract

Copper sulfate and trichlorfon are commonly used in aquaculture. They are often used alone or in combination to kill pathogens and parasites. However, there are few studies evaluating the toxic effects of copper sulfate and trichlorfon on fish. The intestine is an important digestive and immune tissue for fish, which is essential for the growth and development. In this study, zebrafish were used as the research model to detect the toxic effects of copper sulfate (0.5 mg/L) and trichlorfon (0.5 mg/L) at common production concentrations on the fish intestine. The results showed that copper sulfate and trichlorfon significantly induced the activities of intestinal catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX), and alkaline phosphatase (AKP), but had no significant effects on intestinal histology after short-term exposure for 7 days. Following 21 days of long-term exposure, copper sulfate and trichlorfon could significantly induce intestinal mucosal damage, and inhibit the activity of antioxidant enzymes, and the expression of tight junction protein genes tight junction protein 1 (ZO1), claudin 1 (Cldn1), and occludin (Oclna) in the zebrafish intestine. These results suggested that copper sulfate and trichlorfon probably induced intestinal oxidative stress injury by inhibiting the activity of antioxidant enzymes, or induced intestinal mucosal damage by inhibiting the expression of intestinal tight junction protein genes. Moreover, the combined exposure of copper sulfate and trichlorfon was more toxic than the single exposure, which suggest the toxicity of copper sulfate and trichlorfon had a synergistic effect. The present results suggest that copper sulfate and trichlorfon should be used with caution in aquaculture.