Regulation of salivary secretion : dynamic analysis by confocal laser microscopy

大鼠腮腺腺泡细胞有两个分泌系统，受不同的受体和信号转导机制调节。刺激β-肾上腺素能受体通过环磷酸腺苷的胞吐作用来释放酶，而刺激α-肾上腺素能受体和M胆碱能受体则通过磷脂酰肌醇和钙离子来触发体液分泌。活的腮腺腺泡细胞被β-激动剂异丙肾上腺素和毒扁豆碱激动剂卡巴胆碱刺激后，共聚焦显微镜显示了两种胞吐机制。异丙肾上腺素引起胞吐，既不涉及腔膜的大体增大，也不涉及光镜下可检测到的内吞。相反，在卡巴胆碱刺激的细胞中观察到了这两种膜事件。佛波酯TPA、thapsigarin、A23187和H-7结合F-肌动蛋白染色的使用表明，微丝和钙，而不是蛋白激酶C，是区分这些过程的重要调节因素。还观察到，在分泌期，腺泡的紧密连接通透性增加，以允许大分子通过具有灵活的大小选择性特征的细胞旁途径渗透。

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.