TOXIC EFFECT OF CADMIUM ON THE LIVER OF ADULT RATS AND THE PROTECTIVE ROLE OF ZINC SUPPLEMENTATION: LIGHT AND ELECTRON MICROSCOPIC STUDY
Hanan E.L. Mokhtar
Department of Anatomy, Faculty of Medicine, Zagazig University
Background: Cadmium (Cd) is a very toxic heavy metal and an important environmental pollutant which is present in soil, water, air, food and cigarette smoke. Several morphological changes in the hepatic tissue were observed after exposure to Cd. A growing biochemical interest has been focused on factors that can protect toxic effect of Cd. Nutritional status, including zinc (Zn) intake, is one of them.Aim of work: The aim of the present research was to assess the toxic effects of Cadmium (Cd) on the liver of the adult rats and to investigate the possible protective role of zinc supplementation during Cd exposure by histological and ultrastructural study. Material and methods: Thirty adult albino rats, 60-day-old (weighing 250-300g) were obtained from laboratory animal farm, Faculty of Veterinary medicine, Zagazig University, and were divided into three groups, every group contained 10 animals. Control group received tap water and balanced diet, Cd exposed group: animals were exposed to cadmium chloride only (20 mg /kg/day) and Cd and Zn treated group: animals were exposed to cadmium chloride and zinc sulphate (Zn) with the same timeline [Cd (20 mg /kg/day) and Zn (1 mg /kg/day)]. The above mentioned chemicals were given orally per day by gastric feeding tube for six weeks. At the end of the experimental period, the rats were sacrificed under anesthesia. Pieces from the liver were rapidly removed and were utilized for histological and electron microscopic examinations. Results: By light microscopy, in the cadmium exposed groups, the results showed severe histological and cytological alterations including distortion of the radial arrangements of hepatic cords, vascular and sinusoidal dilatation, vascular congestion, some inflammatory infiltration in vicinity and around central vein, thickening of the periportal connective tissue surrounding portal vein, cell necrosis, and increase in the nuclear size with expansion of heterochromatin fields. However, by electron microscope, the changes induced by Cd administration were; a losing of regular compartmentalization of the cytoplasm, cytoplasmic vacuolar degeneration, mitochondrial degenerative changes including swelling associated with translucent matrix and destructed cristae, rER degeneration and fragmentation, excess cells atrophy (necrosis or apoptosis), increased number of the lysosomes and depletion in the glycogen content. However, in the Cd and Zn treated groups, all the previous changes were absent and the liver and its cells appeared normal as compared to the normal control group. Conclusion: On the basis of this study, it can be concluded that, in the cadmium exposed liver, there were severe histological and ultrastructural alterations. Zn supply has protective effect in the prevention from Cd-induced structural damage in the liver. Further studies should be conducted to better understand the protective mechanisms of concomitant treatment by Zn.