Some effects of endosulfan on nile tilapia (Oreochromis niloticus)

Endosulfan is a chlorinated cyclodiene insecticide, toxic for aquatic life. In order to evaluate some of its effects tilapias were fed a diet containing endosulfan (1 mg g(-1)food) during three weeks. Total T3 plasma levels were evaluated and we found that exposed animals (1.99+/-0.05 ng ml(-1)) presented lower levels than control (2.25+/-0.19 ng ml(-1)). In vitro assays of plasma incubated with labelled hormone revealed a different TH binding protein pattern for the exposed animals. Endosulfan exposure leads to a decrease on plasma cortisol, from 235.94+/-56.98 ng ml(-1) on control to 44.45+/-3.56 ng ml(-1) on treated animals, that may explain the decline found on both gill and kidney Na+,K+-ATPase activity. The liver cytochrome P450 activity showed an increase on exposed tilapias.