Objective To observe the protective effect of ischemic preconditioning ( IPC) on the rat submandibular gland after ischemia-reperfusion ( I/R) injury and to investigate the mechanism .Methods Forty-eight healthy male Wist-ar rats were randomly divided into the observation group and model group , 24 in each group .The right glands of rats in both groups received the I/R injury to make the I/R injury models .The glands of the observation group were obtained by 3 min of ischemia , followed by 3 min of reperfusion , and we performed three times before modeling .The left glands were taken as the control group .Salivary secretion , histological changes , alternations of tight junctions ( TJs) and mACh-recep-tor levels in 6 rats were detected at different time points (1 h, 12 h, 24 h and 72 h after I/R).Results In the control group, the salivary secretion , histological changes , alternations of tight junctions ( TJs) and mACh-receptor expression lev-els were all normal .In the model group , the secretion of the glands significantly decreased after I /R 1 h and 12 h, and it showed a slightly lower in the observation group .The secretion of both groups gradually increased at 24 h and got back to normal at 72 h after reperfusion .Cellular atrophy , inflammatory cells infiltration , tissue edema , the collapse and reduced widths of TJs were observed especially after reperfusion for 12 h in the model group , a little part showed the status and the reaction was lighter in the observation group .The level of mACh-receptor exhibited the same tendency , and lower mACh-receptor levels at 12 h after reperfusion were observed in the model group;while in the observation group , it gradually re-turned to normal.Conclusion IPC has the protective effect on the rat submandibular gland after I /R injury, whose mech-anism may be related with the down-regulation of mACh-receptor and protection of TJs .%目的：观察缺血预处理（ IPC）对下颌下腺缺血再灌注（ I／R）损伤大鼠的保护作用，并探讨其机制。方法将48只大鼠随机分为模型组和观察组各24只，均制作右侧下颌下腺I／R损伤模型。观察组在制模前行IPC，夹闭颌外动脉下颌下腺供血支3 min，再灌注3 min，重复3次。以左侧下颌下腺作为对照组。再灌注1、12、24、72 h，取6只大鼠检测各组腺体分泌量、组织学变化、紧密连接结构及M受体表达情况。结果对照组腺体分泌量、组织形态、紧密连接结构及M受体表达情况均正常。 I／R后1、12 h，模型组腺体分泌量明显降低，观察组稍有降低，24 h时两组分泌量开始增加，至72 h逐渐恢复正常。模型组腺实质细胞萎缩，间质水肿及炎症浸润，电镜下超微结构观察显示紧密连接结构破坏，宽度降低，均在再灌注12 h后最为严重，观察组部分腺体组织出现上述情况，且反应较轻。模型组I／R后，M受体水平1、12 h下降明显，观察组稍有下降，72 h时逐渐恢复。结论 IPC对下颌下腺I／R损伤大鼠具有保护作用，其机制与上调下颌下腺M受体的表达、保护下颌下腺紧密连接结构有关。
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