الفهرس 
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Abstract
The present study was conducted to investigate the effect of oral administration of immunosuppressive drug Tacrolimus on the mucous membrane of the tongues of adult male albino rats and the salivary glands of the tongue.
Thirty healthy adult male albino rats with body weight ranging from 150 to 180 grams were used in this investigation.
The animals were divided as follows:
group 1.1: consisted of 15 rats served as control and received distilled water using curved metallic oropharyngeal tube.
group 2.1: consisted of 15 rats and were treated with immunosuppressive drug tacrolimus dissolved in distilled water in daily oral dose of 0.5 mg/kg body weight using curved metallic oropharyngeal tube.
The percentage of mortality for each group was calculated and recorded. Gross examinationof the head and neck area of each animal was carried out throughout the whole experimental period which lasted for three months.
At the end of the experiment the rats of different groups were sacrificed by cervical dislocation. The tongues were dissected out, fixed in 10% neutral buffered formalin, processed, embedded in paraffin, sectioned and stained with:
• Hematoxylin and eosin for histological evaluation.
• Masson’s trichrome stain for demonstration of collagen fibers.
• Immunohistochemical localization of the proliferating cell nuclear antigen (PCNA) and its labeling index were calculated and treated statistically.
Representative tongue specimens from each group were chosen, fixed, dehydrated and gold sputtered under vacuum and were examined with scanning electron microscope.
Results:
Histological results:
Histological sections of tongues of rats treated with tacrolimus showed alteration of their normal structure. The mucous membrane of both dorsal and ventral surfaces showed marked atrophy and degeneration of the epithelium. The filiform papillae showed marked atrophy, loss of its normal sharp conical shape with apparent decrease in their numbers. The fungiform papillae were also atrophic, losing their characteristic mushroom like shape with degenerated cells of their taste buds. The circumvallate papillae appeared shrunken with deepened furrows around them and aggregation of inflammatory cells below its trough.
The collagen fibers of the lamina propria showed marked dissociation and degeneration with dilatation of blood vessels that appeared engorged with blood.