Abstract: Objective: To investigate the roles of apoptosis and mitosis in the regeneration of rat parotid gland following release from duct ligation. Methods: The excretory duct was double ligated with metal-clip unilaterally near the hilum in order to induce atrophy of the parotid gland, and after 2 weeks of ligation(day 0)the double-ligated duct was reopened from 0 to 21 days in order to enable parotid gland regeneration. The evolving gland were examined with HE-staining, AB-PAS staining technique and immunohistochemistry for proliferating cell nuclear antigen(PCNA)as a marker of proliferating cells and Caspase3 as a marker of apoptotic cells. Results: After 14days ligation, the vast majority of acinus and the zymogen granules were replaced by the ductal structure. But during the regeneration of parotid gland, many residual and newly formed acinar cells were identified by HE and AB-PAS staining accompanying increasing zymogen granules. There were occasional PCNA-positive acinar or duct cells in ligated gland, but after 3d of the release of metal-clip, many PCNA-positive cells were seen especially acinar cells between 3d to 7d, thereafter PCNA-positive cells decreased in number.During the regeneration of parotid glands, the Caspase3-positive cells were very rarely observed in 0d, but Caspase3-positive numbers decreased after that. The difference of PCNA-positive numbers were statistically significant between each group (P<0.05)and the reaction of acinar cells compared to duct cells were significantly different at each point of the experimental group(P<0.05). Conclusion: During regeneration of the parotid gland, most acinar cells regeneration from the residual acinar cells at the peripheral region of lobules and the apoptosis of did not play important roles in the regeneration of rat parotid gland after 2 weeks duct-ligation.

Key words: Regeneration , Apoptosis , Salivary glands