Morphological changes in duodenal epithelium of Japanese quail after chronic cadmium exposure

Our study investigated morphological changes in enterocytes of adult Japanese quails that were given cadmium (CdCl₂) perorally and individually by tube, dissolved in water at a dose of 0.24 mg Cd per animal per day, for 57 and 118 days. The aim of our study was to observe chronic effects of cadmium on the structure of duodenal epithelium by means of light microscopy (LM) and transmission electron microscopy (TEM). On day 57, following peroral administration of cadmium, necrotizing enterocytes were found in the apical part of intestinal villi and their occurrence was only sporadic. Particularly on day 118 following cadmium administration, we were able to observe clusters of 2-3 necrotizing cells in the apical part of intestinal villi. However, the structure and ultrastructure of goblet cells was normal. The most notable finding in ultrastructure of all enterocytes of treated animals was the damage to cell organelles. Mitochondria and cisternae of the endoplasmic reticulum were more or less damaged and the cytoplasm contained flocculent material, particularly in the basal part of enterocytes. Some enterocytes exhibited signs of necrosis, shrivelled nucleus and damaged organelles within the markedly electrondense cytoplasm. Microvilli on the apical surface of these enterocytes were damaged and disintegrated. Junctions between cells of the intestinal epithelium were disturbed, and a present of intracellular plaques associated with the adhering and occluding junctions was observed. Cadmium caused the formation of gaps within the specialized junctional complexes, and injury to enterocytes results in the breakdown of the intercellular attachments and the sloughing of the injured cells into the intestinal lumen.