Histological and immunohistochemical evaluation for the effect of pilocarpine and quercetin on gamma-irradiated parotid salivary glands

Radiotherapy of patients with head and neck tumors usually causes damage to the salivary glands since these are most frequently included in the field of irradiation. This study aims at investigating the possible protective effect of pilocarpine or quercetin against radiation induced parotid gland damage. Forty-five adult male rats were divided randomly into three main groups as follows: Radiation group where the rats were exposed to a single whole body 6Gy γ-irradiation; pilocarpine- and quercetin-radiation groups where the rats injected intrapretoneally by a single dose of pilocarpine (0.2mg/kg) or quercetin (1.25g/kg), respectively, 30min later exposed to a single whole body 6Gy γ-irradiation. The parotid glands were stained with hematoxylin and eosin and immunohistochemical reaction for vascular endothelial growth factor A (VEGF-A). Irradiated glands revealed massive acinar atrophy, degeneration and cytoplasmic vacuolization while, the ducts showed cytoplasmic vacuolizations with loss of regular cell architecture. Pilocarpine or quercetin treatment before radiation exposure offered some protection effect manifested as reduced acinaratrophy, degeneration and vacuolization. The ducts showed mild cellular vacuolizations. Regarding VEGF-A immunoreactivity, gamma irradiated parotid gland showed intense expression and significantly higher area that has persisted up to sixteen weeks. Pilocarpine or quercetin treatment was associated with lesser degree and significantly lower area percent of VEGF-A expressionas compared to the radiation group. Pilocarpine or quercetin has some improvement for the injurious effects of radiation on salivary glands so, they can be used as radioprotective agents before radiotherapy schedules to decrease radiation side effects on salivary glands.