Evaluation of intestinal toxicity following single and co-exposure of cadmium chloride and mercury chloride in adult female zebrafish

The study was carried out to explore the toxicological effect of cadmium chloride (CdCl₂, 1 mg/L) and mercury chloride (HgCl₂, 30 |jg/L) on the intestines of adult female zebrafish following simultaneous exposure for 21 days. At the end of exposure, the SOD activity in intestinal tissue was significantly high in all toxicity groups compared to the control group with the highest activity in the Hg exposed group. The catalase activity was at par in all toxicity groups and non-significantly differs from that of control group. While, GSH level was significantly decreased in all toxicity groups compared to control group without significant difference between toxicity groups. However, the levels of MDA were significantly high in all toxicity groups and the highest level in zebrafish exposed to mercury alone compared to that of the control group. The SOD and CAT mRNA expression levels were slightly up-regulated with non-significant down regulation of Nrf2 gene (nuclear factor-erythroid-2-related factor 2). Marked histological changes were noticed in the intestine of zebrafish exposed to Hg and Cd + Hg compared to Cd alone. Based on histological observation, it was inferred that there may be a possibility of more structural damage to intestine due to exposure of binary mixture of cadmium and mercury