Regulation of salivary secretion : dynamic analysis by confocal laser microscopy

大鼠腮腺腺泡细胞具有两个分泌系统，受不同受体和信号转导机制的调控。刺激β -肾上腺素受体可通过环AMP通过胞吐释放酶，而刺激α -肾上腺素受体和毒蕈碱胆碱受体可触发由磷酸肌苷和钙介导的液体分泌。用β -激动剂异丙肾上腺素和毒蕈碱激动剂卡巴醇刺激活腮腺腺泡细胞的共聚焦显微镜显示了两种胞外分泌机制。异丙肾上腺素引起的胞吐既不包括腔膜的肉眼扩大，也不包括光镜下可检测到的胞吞作用。相反，这两种膜事件在受乙醇刺激的细胞中被观察到。使用phorbol酯TPA、Thapsigargin、A23187和H-7结合F-actin染色表明，微丝和钙，而不是蛋白激酶C，是这些过程的重要调节因子。我们还观察到，在分泌期，腺泡的紧密连接通透性增加，允许大分子通过具有灵活大小选择性的细胞旁途径渗透。

Rat parotid acinar cells possess two secretory systems regulated by different receptor and signal transduction mechanisms. Stimulation of the beta-adrenoceptor leads to enzyme release by exocytosis via cyclic AMP,while stimulation of alpha-adrenoceptors and muscarinic cholinoceptors triggers fluid secretion mediated by phosphoinositides and calcium. Confocal microscopy of living parotid acinar cells stimulated with the beta-agonist isoproterenol and the muscarinic agonist carbachol have shown two exocytosis mechanisms. Isoproterenol evoked exocytosis involving neither the gross enlargement of luminal membrane nor the light microscopically detectable endocytosis. Both of these membrane events were instead observed in cells stimulated with carbachol. The use of phorbol ester TPA,Thapsigargin, A23187 and H-7 in conjunction with the F-actin staining has suggested that microfilaments and calcium, but not protein kinase C,are important regulators for the discrimination of these processes.It was also obeserved that under the secretory phase the tight junctional permeability in acini increase to allow permeation of large molecules through the paracellular pathway with flexible size-selectivity characteristics.