Zinc sulfate chronic exposure effects on large intestine of adult Wistar rats: a histological evaluation

Abstract: The present study aimed to investigate possible morphological changes in the large intestine of adult Wistar rats submitted to chronic exposure to zinc sulfate at different doses. The animals were divided into three groups: control, treated with 5mg and treated with 20mg of zinc sulfate. The experiment had 56 days of exposure period and after this period the animals were anesthetized and euthanized. After dissection, a fragment of the cranial portion of the ascending colon of each animal was removed, fixed in Karnovsky solution for 24 hours, dehydrated in a growing ethanolic series and included in glycolmethacrylate resin. In a manual microtome, slices of 3μm thickness were obtained and then, stained with blue toluidine, for tissue description and morphometric analysis. The samples were also also submitted to histochemical techniques: Periodic acid of Schiff (PAS) and Alcian Blue (pH 2.5), for marking neutral and acidic mucus producing cells, respectively. The morphological parameters analyzed were: crypt depth, intestinal epithelium height, and number of PAS-positive and Alcian Blue-positive goblet cells. A decrease of neutral mucin-producing cells number and an increase in the height of the intestinal epithelium were observed in the animals treated with 20 mg of zinc sulfate. These results indicate morphological changes in the large intestine due to chronic zinc exposure, indicating a stress condition. Keywords: Toxicity, Zinc, Intestine, Mammal, Morphology.