Wong H M, Tepperman B L
Department of Physiology, University of Western Ontario, London, Canada.
Am J Physiol. 1994 Jul;267(1 Pt 1):G1-9. doi: 10.1152/ajpgi.1994.267.1.G1.
In the present study, we have examined the role of reduced glutathione (GSH) in the modulation of Ca2+ ionophore A-23187-induced gastric mucosal cellular disruption. Experiments were conducted using cells isolated from rabbit oxyntic mucosa. Cell injury was assessed by release of the lysosomal enzyme acid phosphatase, by trypan blue dye uptake, and by examination of lipid peroxidation. Cellular GSH was assessed spectrophotometrically by measuring total soluble reduced thiol content. Ionophore A-23187 (3-25 microM) induced a concentration-dependent injury to mucosal cells and a concentration-dependent reduction in cellular GSH content. Removal of Ca2+ from the incubation medium abolished both the disruptive action and the GSH-lowering effect of A-23187. Gastric cellular GSH content was reduced significantly by preincubation of cells with an agent that depletes reduced sulfhydryls, diethyl maleate (DEM; 1 mM). Furthermore, DEM significantly augmented cellular disruption in response to A-23187. Similarly, incubation of cells with L-cysteine (1 mM), a stimulant of glutathione synthesis, increased mucosal cellular GSH content and decreased the cellular disruptive effect of A-23187. Exogenous addition of GSH to the cell suspension significantly reduced Ca2+ ionophore-induced cellular disruption and hastened the recovery of cellular free Ca2+ concentration ([Ca2+]) to baseline values. Similarly, exogenous GSH reduced cellular disruption produced by cyclopiazonic acid and thapsigargin, agents that increase intracellular [Ca2+] ([Ca2+]i) by inhibiting Ca2+ sequestration. These data suggest that a sustained increase in [Ca2+]i contributes to the pathogenesis of gastric mucosal cellular injury. This effect appears to be mediated by a reduction in the cellular content of GSH.
在本研究中，我们检测了还原型谷胱甘肽（GSH）在调节钙离子载体A - 23187诱导的胃黏膜细胞破坏中的作用。实验使用从兔胃体黏膜分离的细胞进行。通过溶酶体酶酸性磷酸酶的释放、台盼蓝染料摄取以及脂质过氧化检测来评估细胞损伤。通过测量总可溶性还原巯基含量，用分光光度法评估细胞内GSH。离子载体A - 23187（3 - 25 microM）对黏膜细胞造成浓度依赖性损伤，并使细胞内GSH含量呈浓度依赖性降低。从孵育培养基中去除钙离子可消除A - 23187的破坏作用和降低GSH的作用。用耗尽还原巯基的试剂马来酸二乙酯（DEM；1 mM）预孵育细胞，可显著降低胃细胞内GSH含量。此外，DEM显著增强了细胞对A - 23187的破坏反应。同样，用谷胱甘肽合成刺激剂L - 半胱氨酸（1 mM）孵育细胞，可增加黏膜细胞内GSH含量，并降低A - 23187对细胞的破坏作用。向细胞悬液中额外添加GSH可显著减少钙离子载体诱导的细胞破坏，并加速细胞游离钙离子浓度（[Ca2+]）恢复至基线值。同样，外源性GSH减少了由环匹阿尼酸和毒胡萝卜素产生的细胞破坏，这两种试剂通过抑制钙离子螯合增加细胞内[Ca2+]（[Ca2+]i）。这些数据表明，细胞内[Ca2+]i的持续升高促成了胃黏膜细胞损伤的发病机制。这种作用似乎是由细胞内GSH含量的降低介导的。
