الفهرس 
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Abstract
Lead is regarded as a potent toxin, Animal models show that salivary glands are liable to destruction in exposure to metals. chronic exposure to lead can elevate the oxidative stress and reduce the antioxidant enzyme activities mainly by generation of reactive oxygen species (ROS), which leads to cytotoxicity in multiple tissues in the body.
Our study was carried out to evaluate the histological and ultrastructural effects of lead acetate and sesame oil on parotid glands in an albino rat model.
This study was conducted on twenty four adult male albino rats weighing between (180–200) 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): 8 rats were kept under normal condition and received 1 ml distilled water orally once daily for 5 weeks and considered as control group.
• group B (study group1) (Lead acetate group): 8 rats were given 500 mg pb acetate/kg diet once daily for 5 weeks.
• group C (study group 2) (Lead acetate + sesame oil): 8 rats were administered 500 mg pb acetate/kg diet concurrently with sesame oil (5 ml/kg body wt/day) orally by gavage daily for 5 weeks.
Rats were euthanized after 5 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
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morphometric measurements (measuring surface area of the acini and ductal lumen), 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 (Lead acetate 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 loss of architecture. Secretory striated ducts were dilated, lined with atrophic epithelium, and had stagnated secretion. The characteristic basal striations of the ductal cells were partially lost. Connective tissue septa showed an outstanding fibrosis.
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, swollen mitochondria, extensively dilated cisterna of rER.
In group C (group received a daily dose of Lead acetate and sesame oil), the histological as well as the ultrastructural examination of the specimens showed a well noticed preservation of the parotid gland structure in comparison with the group received lead acetate only. Acinar and ductal cells appeared normal to great extent (similar to control group) with minor atrophic changes.
Regarding the histomorphometric results, Lead group measurements showed a highly significant decrease in the mean surface area of serous acini when compared with the control group. A significant decrease was also reported on comparing Lead + sesame oil group to the control group. Lead + sesame oil group recorded a significant increase in the mean surface area of the acini when compared to Lead group. While ducts in Lead group showed increase in luminal area in comparison to control group. And Lead+ sesame oil group showed intermediate results in ductal lumen enlargement.
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from this study, we concluded that ingestion of lead acetate in diet of albino rats may result in degenerative changes in parotid gland acini and ducts and coadministration of sesame oil was highly effective in protecting gland tissue against lead acetate induced damage.