Changes in carbohydrate metabolism,oxidative stress and loss of cortisol secretion in adrenocortica l cells of Oreochromis niloticus exposed in vitro to endosulfan

The effects of endosulfan, an organochlorine pesticide regularly used in Niger Delta ecological zone, were examined and also its effects on various biochemical parameters in the serum of Oreochromis niloticus, a dominant fish species in Nigeria. One hundred and fifty juveniles of O. niloticus were used for the toxicity study. Lethal concentration of 50% mortality of sample (LC₅₀) was determined using semi-static method. From the result of the LC₅₀ determination, lower concentrations of endosulfan were prepared for sublethal test. Five fish per test concentration in three replicates were exposed to varying concentrations of endosulfan. Glucose level and the enzyme activities were measured spectrophotometrically at the end of 28 days of exposure. Glucose levels and glutathione-S-transferase activities were significantly (p < 0.05) higher than the control and the concentrations increased with increasing concentration of the toxicant and exposure duration. Cortisol secretion was significantly (p = 0.05) lower in the treated fish than the control. These findings indicated that endosulfan altered all the investigated parameters, which is an indication of their suitability as markers for fish and other aquatic organism toxicity study.