Regulation of salivary secretion : dynamic analysis by confocal laser microscopy

大鼠腮腺腺泡细胞具有两种分泌系统，受不同受体和信号转导机制的调节。β-肾上腺素受体的刺激通过环AMP的胞吐作用导致酶释放，而α-肾上腺素受体和毒蕈碱胆碱受体的刺激触发由磷酸肌醇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胆碱刺激的活腮腺腺泡细胞的共聚焦显微镜显示了两种胞吐机制。异丙肾上腺素诱发的胞吐作用既不涉及管腔膜的大体增大，也不涉及光镜下可检测到的内吞作用。这两种膜事件都在卡巴胆碱刺激的细胞中观察到。佛波醇酯TPA、毒胡萝卜素、A23187和H-7与F-肌动蛋白染色的联合使用表明，微丝和钙，而不是蛋白激酶C，也观察到在分泌期腺泡紧密连接的通透性增加，允许大分子通过具有灵活大小的细胞旁途径渗透，选择性特征

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.