Histological Changes Of The Atrophied Rat Parotid Gland Induced By Duct-ligated Injury

Objective:To investigate the changes of parotid gland of Wistar rats during the atrophy progress of duct-ligated and we checked the histologic changes of atrophied glands and the changes of Caspase3, Ki-67, and Calponin protein. Methods:Sixty male Wistar rats of 7-weeks-old were used as sample. The excretory duct was double ligated with 3-0 silk unilaterally near the hilum of the parotid gland in order to induce atrophy of the parotid gland. Then the operated animals were sacrificed at the time point of 0,1,3,5,7,10,14,21 or 30 days after operation respectively and the evolving gland were routinely examined with HE and AB-PAS staining technique methods and the SP-immunohistochemistry for Caspase3, Ki-67,Calponin protein respectively. Results:1. Morphology observation. Compared with the control parotid glands, the volume decreased gradually in the operation groups with the duct double-ligated accompany with color and character changes. 2. Histological observation. After the duct ligation, the vast majority of acinar cells and zymogen granules were disappeared respectively though the methods of HE and AB-PAS staining. By the day of 30-days after operation, only dilated ducts and residual acinar cells were identified clearly at the peripheral region of lobule. During the atrophy of duct-ligated parotid glands, the Caspase3 protein positive cells were very rarely observed in 0-days group, but the numbers increased subsequently. By the 5-days group of the duct ligation, the Caspase3 protein positive cells reached a peak, after that the Caspase3 protein positive cells decreased in number identified by immunohistochemistry. There was occasional Ki-67 protein positive cells in the 0-days group, but after 3-days group of the duct ligation the Ki-67 protein positive cells reached a peak, subsequently the Ki-67 protein positive cells decreased in number. The numbers of The Calponin protein positive cells by 3-days group, increased and reached a peak at the 14-days group of the duct ligation, after that the Calponin protein positive cells decreased in number. The difference of the Caspase3, Ki-67 and Calponin protein positive cells were statistically significant between each group(P<0.05). Conclusion:During atrophy of the parotid gland, most acinar cells and the zymogen granules disappeared and the gland peripherals were replaced by dilated ducts. But there were still some residual acinar-like cells at the peripheral region of gland lobules after 30-days continuously duct-ligation. Whether these residual acinar-like cells can play important roles in the regeneration of atrophied-rat parotid gland will to be demonstrated.