Document Type : Original Article
Authors
1
Department of Forensic Medicine and Clinical Toxicology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
2
Department of Histology and Cell Biology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
3
Department of Medical Biochemistry, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
Abstract
Introduction: Aroclor 1254 is a commercial mixture of polychlorinated biphenyls used in transformers, capacitors, paints, pesticides and others. The effect of Aroclor 1254 on endocrine system, especially thyroid gland has been a point of research interest.
Aim of the work: The present study was, therefore designed specifically to investigate the possible toxic effect of Aroclor 1254 on thyroid follicular cells of adult male albino rats and to assess the possible protective role of zinc sulphate.
Material and methods: The study was carried out on 45 adult male albino rats that were randomly divided into 3 equal groups. Group I or the control group, which was further, divided into 3 equal subgroups, (5 rats each): received either normal saline or corn oil or zinc sulphate, respectively, orally for 4 weeks. Group II: Aroclor 1254 dissolved in corn oil in a dose of 4mg /kg.b.w/day for 4 weeks. Group III: received Aroclor 1254 dissolved in corn oil in a dose of 4mg /kg.b.w/day with concomitant administration of zn sulphate at a dose of 200mg/kg.b.w/day for 4 weeks. After 28 days, the animals were sacrificed and blood samples were subjected to hormonal assay for T3, T4 and TSH levels. Malondialedehyde (MDA) and reduced glutathione (GSH) were also assessed.
Results: Biochemical assays showed a significant decrease in serum GSH, total antioxidant capacity, T3 and T4 levels in the aroclor treated group than both control and protected group. On contrary, a significant increase in serum MDA and TSH levels was recorded in Aroclor treated group than other two groups. Microscopic examination of thyroid gland follicles in Aroclor 1254 treated rats revealed evident histological changes. Most of the follicles appeared smaller compared to the control group. Excessive vacuolation of the colloid at the interphase with the lining epithelial cells was seen. Moreover, most of the follicles appeared lined with high cuboidal epithelial cells with foci of epithelial hyperplasia. Ultrastructural alterations in follicular cells were detected which appeared as high columnar cells with irregular microvilli. Numerous rough endoplasmic reticulum with extensively dilated cisternae that were filled with flocculent material were demonstrated. On examination of the group III, a marked improvement in the histological features of thyroid follicles was noticed.
Conclusion: These results suggest that PCB induces oxidative stress in rats as well as hypothyroidism; these effects could be reversed by the administration of zinc sulphate. The decrease in T3 and T4 levels induced compensatory effects in the thyroid, visible as hyperactivity of the thyroid epithelia.
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