EFFECT OF CADMIUM ON THE CARDIAC MYOCYTES IN ADULT RABBIT: A LIGHT AND AN ELECTRON MICROSCOPIC STUDY Fathy Ahmed Fetouh, Amal Al Shahat Ibrahim, Eman M.A. Abdelghany Department of Anatomy, Faculty of Medicine, Zagazig University Egypt. J. Med. Sci. 33 (1) June 2012: 385-397. Abstract Background: Cadmium (Cd) possesses a significant threat to the human population and environment. The most relevant sources for Cd uptake by human are however, cigarette smoking, food and exhaust of gases. Objective: The present work aimed to study the histological and ultrastruc-tural effect of cadmium on the cardiac myocytes in rabbit. Materials and methods: 2 groups of Egyptian adult male rabbits (6 rabbits for each) were used for this study. The lot group was used as a control. The 2'd group (experimental) was exposed to cadmium chloride (CdCIZ) intake in a dose of 100 mg CdCIZ/1 in drinking water for 24 weeks. The animals were anaesthetized and rapidly dissected. Heart specimens were obtained and processed for light and electron microscopic examination. Results: The cadmium had adverse effects on the cardiac myocytes in Cd treated rabbits in comparison to those of rabbits in the control group where extensive haemorrhage was seen and the blood vessels showed endothelial thickening with peri-vascular infiltration of inflammatory cells. Regarding the ultrastructure of the cardiac myocytes, the myofibrils showed contraction bands, focal myofibrils degeneration with sarcomere disorganization and scattered masses of myofilaments. The mitochondria were damaged and appeared swollen with loss of transverse cristae and degeneration of their limiting membranes. Multiple vacuolization were seen between the myofilaments. The nucleus appeared irregular in shape, heterochromatic with deep invagination of the nuclear membrane. The junctional complexes were disrupted. Conclusion: The cadmium has adverse effects on the structure of cardiac myocytes. So, extreme attention must be taken to prevent the release of cadmium to the environment. Key words: Cadmium, Cardiac myocytes, Histology, Ultrastructure.