Shimamoto Chikao, Umegaki Eiji, Katsu Ken-ichi, Kato Masumi, Fujiwara Shoko, Kubota Takahiro, Nakahari Takashi
Central Research Laboratory (Nakahari Project), Osaka Medical College, Takatsuki 569-8686, Japan.
Am J Physiol Gastrointest Liver Physiol. 2007 Oct;293(4):G824-37. doi: 10.1152/ajpgi.00125.2007. Epub 2007 Aug 2.
The effects of intracellular Cl- concentration ([Cl-]i) on acetylcholine (ACh)-stimulated exocytosis were studied in guinea pig antral mucous cells by video microscopy. ACh activated Ca2+-regulated exocytosis (an initial phase followed by a sustained phase). Bumetanide (20 microM) or a Cl- -free (NO3-) solution enhanced it; in contrast, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, a Cl- channel blocker) decreased it and eliminated the enhancement induced by bumetanide or NO3- solution. ACh and Ca2+ dose-response studies demonstrated that NO3- solution does not shift their dose-response curves, and ATP depletion studies by dinitrophenol or anoxia demonstrated that exposure of NO3- solution prior to ATP depletion induced an enhanced initial phase followed by a sustained phase, whereas exposure of NO3- solution after ATP depletion induced only a sustained phase. Intracellular Ca2+ concentration ([Ca2+]i) measurements showed that bumetanide and NO3- solution enhanced the ACh-stimulated [Ca2+]i increase. Measurements of [Cl-]i revealed that ACh decreases [Cl-]i and that bumetanide and NO3- solution decreased [Cl-]i and enhanced the ACh-evoked [Cl-]i decrease; in contrast, NPPB increased [Cl-]i and inhibited the [Cl-]i decrease induced by ACh, bumetanide, or NO3- solution. These suggest that [Cl-]i modulates [Ca2+]i increase and ATP-dependent priming. In conclusion, a decrease in [Cl-]i accelerates ATP-dependent priming and [Ca2+]i increase, which enhance Ca2+-regulated exocytosis in ACh-stimulated antral mucous cells.
通过视频显微镜研究了豚鼠胃窦黏液细胞内氯离子浓度（[Cl-]i）对乙酰胆碱（ACh）刺激的胞吐作用的影响。ACh激活了Ca2+调节的胞吐作用（一个初始阶段接着一个持续阶段）。布美他尼（20微摩尔）或无Cl-（NO3-）溶液增强了该作用；相反，5-硝基-2-（3-苯丙基氨基）苯甲酸（NPPB，一种Cl-通道阻滞剂）减弱了该作用，并消除了布美他尼或NO3-溶液诱导的增强作用。ACh和Ca2+剂量反应研究表明，NO3-溶液不会使它们的剂量反应曲线发生偏移，并且通过二硝基苯酚或缺氧进行的ATP耗竭研究表明，在ATP耗竭之前暴露于NO3-溶液会诱导增强的初始阶段接着一个持续阶段，而在ATP耗竭之后暴露于NO3-溶液仅诱导一个持续阶段。细胞内Ca2+浓度（[Ca2+]i）测量表明，布美他尼和NO3-溶液增强了ACh刺激引起的[Ca2+]i升高。[Cl-]i测量显示，ACh降低[Cl-]i，布美他尼和NO3-溶液降低[Cl-]i并增强了ACh引起的[Cl-]i降低；相反，NPPB升高[Cl-]i并抑制了ACh、布美他尼或NO3-溶液诱导的[Cl-]i降低。这些表明[Cl-]i调节[Ca2+]i升高和ATP依赖性启动。总之，[Cl-]i的降低加速了ATP依赖性启动和[Ca2+]i升高，这增强了ACh刺激的胃窦黏液细胞中Ca2+调节的胞吐作用。
