الفهرس 
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Abstract
Monosodium glutamate is a popular food additive that is applied to many food products to enhance the flavor. food and drug organizations have considered MSG to be generally safe for human consumption however, many studies reported that long term consumption of high doses of this food additive is toxic to different body organs.
Oxidative stress has been believed to be the principal mechanism by which monosodium glutamate could induce toxicity. Therefore, using antioxidants may be effective in protecting against these harmful effects. Vitamin C has a powerful antioxidant role and it is one of the first lines of defense against reactive oxygen species and free radicals.
Our study was carried out to evaluate the histological and ultrastructural effects of monosodium glutamate and vitamin C on parotid glands in an albino rat model.
This study was conducted on thirty adult male albino rats weighing between (150–200) grams. After obtaining approval from the Research Ethics Committee, Faculty of Dentistry, Alexandria University.
Rats were equally divided into 3 equal groups as follows:
group A (control group): 10 rats were kept under normal condition and received 1 ml distilled water orally once daily for 8 weeks.
group B (MSG group): 10 rats received 30 mg/kg bodyweight of monosodium Glutamate dissolved in distilled water orally once daily for 8 weeks.
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group C (MSG + Vit. C group): 10 rats received 30 mg/kg bodyweight of monosodium glutamate dissolved in distilled water followed by 100mg/kg bodyweight vitamin C in distilled water by oral gavage daily for 8 weeks.
Rats were regularly evaluated every week to monitor their general health, activity and bodyweight change throughout the whole experimental period (8 weeks).
Rats were euthanized after 8 weeks by intravenous injection with a lethal dose (100 mg/kg) of pentobarbital sodium. The rats were decapitated, parotid salivary glands were dissected out carefully.
Left parotid glands were fixed in 10% neutral buffered formalin and processed to obtain 5 μm thick sections stained with H&E to be used for light microscopic examination and morphometric measurements (measuring surface area of the acini), while the right glands were immediately fixed in 2.5% glutaraldehyde solution and processed to get ultrathin sections to be examined by transmission electron microscope.
Histological examination of group B (MSG group) sections under the light microscope revealed severe destructive changes of the parotid gland in comparison to control group. Serous acini appeared degenerated with ill-defined boundaries. Acinar cells exhibited severe cytoplasmic vacuoles and apoptotic or pyknotic (crescent shaped) nuclei. Secretory striated ducts were dilated, lined with atrophic epithelium, and were associated with large, congested blood capillaries. The characteristic basal striations of the ductal cells were partially lost. Connective tissue stroma showed an outstanding fibrosis and contained large, dilated blood vessels (BVs).
Electron microscopic examination of group B confirmed the results obtained by the light microscope. Cells of serous acini and ducts exhibited dense heterochromatic nuclei with irregular outline, degenerated mitochondria, extensively dilated cisterna of RER.