Function, structure and regulation of two kinds of Cl^- channels involved in gastric acid secretion

本文研究了酸性分泌细胞基侧膜和顶膜上存在的两种不同的氯离子通道。通常，细胞膜电位由K的平衡电势决定：即K电导决定电势。但在兔壁细胞中，膜电位是由基底膜上的氯离子通道决定的。从膜片钳集成噪声分析实验中发现，单个氯离子通道电导仅为0.3ps。该通道被花生四烯酸(AA)和前列腺素E_2(PG)激活，被GTP-S抑制。在其他类型的细胞中，AA和PG抑制该通道，而GTP-S则激活该通道，这与目前发现的胃Cl-通道相反。通过氯离子通道对细胞膜电位的调节参与了对强酸和应激的细胞保护。壁细胞的隔离导致闭塞的小管的形成，顶膜不能通过微吸管从细胞表面到达。用酸性质子泵抑制剂甲氧基E3810浸泡细胞表面，用紫外光照射S-S交联型抑制剂，测定了细胞的荧光强度。通过对单细胞的图像荧光分析，得到了泵的分布。利用氧合细胞，我们成功地检测到了心尖氯离子通道，但还需要更详细的研究来表征心尖氯离子通道。

Two different Cl- channels which are present in the basolateral and apical membranes of acid secreting cells are studied here. Usually, cell membrane potentials are determined by equilibrium potential to K+ : that is, K+ conductance determines the potential. But in the rabbit parietal cell, the membrane potential was found to be determined by Cl- channel in the basolateral membrane. The single Cl- channel conductance was found to be only 0.3 pS from an experiment of patch clamp-ensemble noise analysis. The Cl- channel was activated by arachidonic acid (AA) and prostaglandin E2 (PG), and inhibited by GTP S. In other types of cells, AA and PG are known to inhibit Cl- channel and GTP S activates the channel, which is in contrary to what found for the present gastric Cl- channel. Regulation of the cell membrane potential via the Cl- Channd engages in cytoprotection against strong gastric acid and stress.Isolation of parietal cells results in formation of occluded canaliculus and the apical membrane is not able to be reached from the cell surface by a micropipette. We found that oxyntic cells isolated from red belly newt expose both the basolateral and apical membranes to the bath medium from an experiment in which acid-activated proton pump inhibitor, methoxy E3810, was poured on the surface of the isolated cell, the S-S cross-linked inhibitor was irradiated with ultraviolet light, and the increase in the fluorescence was measured. The distribution of the pump was obtained from the image fluorescence analysis of single cells. Using the oxyntic cells we succeeded to detect the apical Cl- channel although more detailed study is necessary to characterize the apical Cl- channel.