الفهرس 
Development of Parotid Salivary GlandsOnly 14 pages are availabe for public view
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Abstract
Background: Parotid gland (PG) is a unique major salivary that has distinct structural and functional features. Interestingly, clinical use of radioactive iodine in thyroid disorders resulted in selective damage to PG parenchyma, which was attributed to its ability to concentrate iodine together with presence of tyrosine deiodinase enzyme.Aim of study: The present study aimed to investigate the effect of rat thyroidectomy on PG structure and protein content and to examine the capability of thyroxinsupplementation to alleviate that possible effect.Material and methods: Forty young adult male albino rats were allocated equally into four groups; control, sham-operated, thyroidectomized and supplementation groups.Half of rats of each group were euthanized three weeks after thyroidectomy and the other half after five weeks. Before euthanization, blood samples were taken for serum analysis. Bilateral PGs were dissected and right glands were prepared for structural examinations whereas left glands were prepared for protein analysis and identification using SDS-PAGE and western blot.Results: Thyroidectomized rats revealed significantly higher TSH and lower free T4 than those of other groups. Also, their PGs depicted a newly expressed 300 kDa protein, which was confirmed to be thyroglobulin by western blot. Histologically,some intralobular ducts were filled with colloid-like secretory material. Interestingly,five weeks after thyroidectomy revealed significantly higher free T4 levels than three weeks and displayed altered acinar cells and widened intercellular canaliculi. Some intralobular ducts simulated thyroid-like follicles with colloid-like secretion within their lumen and surrounded by rich capillary plexus. Noteworthy, supplementation group revealed normalization of TSH and free T4 levels after five weeks, though there was significant difference with thyroidectomized group. Remarkably, their PGs depicted vanishment of 300 kDa protein consistent with histological detection of parafollicular-like cells that occasionally disclosed Berbicks-like granules.Conclusion: Thyroidectomy seemed to induce PG to synthesize thyroglobulin protein which disappeared upon thyroxin supplementation.Key words: PG; thyroid gland; thyroidectomy; thyroxin supplementation.