4-TERT-BUTYLPHENOL-INDUCED REPRODUCTIVE ENDOCRINE DISRUPTION IN THE FRESHWATER STINGING CAT FISH HETEROPNEUSTES FOSSILIS

To assess the impact of 4-tert-Butylphenol (4-tBP), an endocrine-disrupting chemical (EDC), on the reproductive cycle of the fish model, Heteropneustes fossilis, biochemical assays and gene expression studies were employed. The median lethal concentration (LC ) of 4-tBP was 50 estimated before subjecting the fishes to antioxidant enzyme assay (catalase: CAT; superoxide dismutase: SOD) and gene (cyp19a1a: ovarian aromatase; vtg: liver vitellogenin) expression studies. After following a standardized set of protocols, the LC (96 hours) value for the exposure 50 of the compound in fish was found to be 27.8 mg/L. The SOD and CAT antioxidant enzyme activity, at one-tenth of the LC (96 hours) value of 4-tBP, was found to be disrupted; thereby, 50 suggesting an increase in the oxidative stress in the fish. Lastly, the same fish tissue samples were taken for gene expression studies, which revealed the upregulation and downregulation of vtg and cyp19a1a genes, respectively. The upregulation of the vtg gene expression and the enhanced synthesis of associated (vtg) protein can be attributed to the structural similarity of 4-tBP with that of the natural estrogens to bind to the receptor, which leads to the downstream protein synthesis mechanism. In contrast, the downregulated cyp19a1a gene can be associated with impairments in ovarian development that can alter the reproductive physiology. Therefore, these results suggest the endocrine-disrupting nature of the compound 4-t-BP in H. fossilis.