Effects of mastication on the secretory and proliferative capabilities of parotid gland in male rat

4周龄大鼠分别饲喂3（4周龄大鼠）-9（13周龄大鼠）东方酵母公司的固体或粉末状MF饲料，用硅化透镜纸培养的腮腺外植体检测腮腺对唾液调节剂（丙二醇和异丙肾上腺素）的反应性（Kawano et al., j . denter .71,1885-1890,1992）。实验结果如下：1) 3-9周龄大鼠（7-13周龄大鼠）的体重增加量为90g（4周龄大鼠）~ 450g（13周龄大鼠），两种饲料组的体重增加量相同，但固体组腮腺的平均重量比粉末组大20%左右。2)固体组（7周龄大鼠）淀粉酶分泌依赖性增高高于粉剂组（9周龄以上大鼠），但两组间无显著差异。3)在整个实验期间（7 ~ 13周龄大鼠），固体组唾液凝集剂诱导的c-fos、c-myc和鸟氨酸脱羧酶mRNA水平及酶活性均高于粉末组。上述结果表明，固体组和粉末组对腮腺淀粉酶分泌和细胞增殖的影响明显大于粉末组，提示物理压力和咀嚼频率参与了腮腺对交感和副交感刺激的反应性。

Four week-old rats were fed for3 (4-week-old rat)-9 weeks (13-week-old rat) with solid or powdered MF feed of Oriental Yeast Co.and the responsiveness of parotid gland to sialagogues (carbachol and isoproterenol) was examined with parotid explants which were cultured on siliconized lens paper (Kawano et al., J.Dent.Res.71,1885-1890,1992).The results were as follows ;1) The increases of body weights, 90g (4-week-old rats) to 450g (13-week-old rats), were the same among the two feed groups but an average weight of parotid gland was heavier (about 20%) in solid group than in powder group in 3-9-week-treated rats (7-13-week-old rats).2) Sialagogue-dependent increase in amylase secretion was higher in solid group than in powder group (7-week-old rats), but no significant difference was observed between two groups of older than 9-week-old rats.3) Sialagogue-induced increases in mRNA levels of c-fos, c-myc and ornithine decarboxylase and activity of the enzyme were higher in solid group than powder group during entire period of experiment (7-13-week-old rats).These results indicate that the effects of carbachol and isoproterenol on amylase secretion and cell proliferation in parotid gland were marked in solid group than in powder group, suggesting that physical pressure and frequency of mastication participate the responsiveness of parotid gland to both sympathetic and parasympathetic stimuli.