Since there is a constant release of trace elements in unnaturally higher concentrations and often in unusual physio-chemical state, the fear of them being hazardous to human health is now an indisputable truth. Once perpetuated in the environment, metals are not readily detoxified by metabolic activity. As a result, they get accumulated contributing to potential environmental hazard. In the present study, the effect of cadmium chloride on thymus of mice has been in investigated. For the experiment, adult healthy male Swiss albino mice were fed with aqueous solution of CdCl₂ prepared by dissolving 20mg of CdCl₂ in 1000ml of distilled water, thus giving a concentration of 20ppm and then administered orally in drinking water ad libitum continuously till the end of experiment. Animals were autopsied by cervical dislocation at each post-treatment interval of 1, 2, 4, 7, 10, 14 and 28 days. Thymus was taken out after autopsy, weighed and fixed in Bouin’s fluid. Then the tissue was dehydrated and embedded in paraffin wax and transverse sections were cut at 5µ and stained in Harri’shaematoxylin-eosin stain for histopathological studies. After cadmium chloride treatment, thymus showed a significant decline in the organo-somatic index value continuously till day 10, and recovering thereafter. Pathological changes after CdCl₂ treatment include necrosis of thymocytes, fibrous tissue proliferation, Pyknosis, Karyolysis, and distortion of Hassal’s corpuscles. Recovery started at a much later interval, and was probably due to the binding of intracellular cadmium to metallothionein which protects the tissue against the cadmium toxicity.

Keywords: Karyolysis, Pyknosis, Metallothionein, Thymocytes, Cadmium Toxicity.