Endocrine stress response in Oreochromis sp from exposure to waterborne cadmium: the plasma cortisol analysis

Cadmium (Cd) is known as one of the most dangerous environmental and industrial pollutants. It has no biological function and accumulates mainly in metabolically active tissue even at low concentrations, which in turn may cause tissue damage. The effect of Cd on the endocrine systems of fish is not well known. To test the hypothesis that Cd is a chemical stressor, Oreochromis sp. were exposed to waterborne cadmium chloride and their endocrine stress response (plasma cortisol) was investigated after 4days and 20days. The plasma cortisol levels were analyzed using reverse-phase high performance liquid chromatography with UV detection ( = 250 nm) after liquid-liquid extraction. The detection limit of the method was found to be 0.87 ng/mL plasma. This study provides evidence that Cd probably causes exhaustion of endocrine systems. Oreochromis sp. exposure to Cd resulted in a 15%-53% and 52%-91% suppression of cortisol release after 4days and 20days of exposure, respectively, in comparison with the control group. The results suggest that Cd still activates the endocrine system at 20days and the interrenal cells of Oreochromis sp. were not impaired after 20days of exposure to Cd.