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

本文研究了两种不同的Cl通道，它们分别存在于分泌酸细胞的基底膜和顶膜上。通常细胞膜电位由对K+的平衡电位决定，即K+电导决定电位。而在家兔顶壁细胞中，膜电位是由基底外侧膜上的Cl-通道决定的。从膜片钳系综噪声分析实验中发现，单Cl通道电导仅为0.3 pS。花生四烯酸（AA）和前列腺素E2 （PG）激活Cl-通道，GTP S抑制Cl-通道。在其他类型的细胞中，已知AA和PG抑制Cl-通道，而GTP S激活Cl-通道，这与目前胃Cl-通道的发现相反。通过Cl-通道调节细胞膜电位参与抗强胃酸和应激的细胞保护。壁细胞的分离导致闭塞小管的形成，微移液管无法从细胞表面到达顶膜。实验发现，将酸活化质子泵抑制剂甲氧基E3810倒在分离的红腹蝾螈细胞表面，用紫外光照射S-S交联抑制剂，并测量其荧光的增加，从而使红腹蝾螈的氧合细胞的基底膜和根尖膜暴露在浴液中。通过单细胞的图像荧光分析得到泵的分布。利用氧合细胞，我们成功地检测到了顶端Cl-通道，但对顶端Cl-通道的表征还需要更详细的研究。

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.