Iantomasi T, Favilli F, Marraccini P, Magaldi T, Bruni P, Vincenzini M T
Department of Biochemical Sciences, University of Firenze, Italy.
Biochim Biophys Acta. 1997 Dec 4;1330(2):274-83. doi: 10.1016/s0005-2736(97)00097-7.
The present study characterizes for the first time a GSH specific transporter in a human intestinal epithelial cell line (I407). GSH metabolism is very important for the antioxidant and detoxifying action of intestine and for the maintenance of the luminal thiol-disulfide ratio involved in regulation mechanisms of the protein activity of epithelial cells. GSH level decreases have been related to physio-pathological alterations either of intestine or other organs. GSH specific transport systems have been identified in membranes of various cell types of rat, mice and rabbit. The presence of a Na+-independent transport system of GSH is confirmed by the similar behaviour of GSH uptake time-courses when Na+ in extracellular uptake medium was replaced with choline+ or K+ as well as by kinetic saturation and by the trans-stimulation effect on GSH uptake in GSH preloaded cells. Moreover, this transporter is activated when cations are present in extracellular medium and it is affected by membrane potential changes with an increase in GSH uptake values when membrane depolarization occurs. The present results also show a remarkable affinity and specificity of this transporter for GSH; in fact, Km value is very low (90 +/- 20 microM) and only compounds strictly related to GSH structure, such as GSH S-conjugates and GSH-ethyl ester, inhibit GSH uptake in 1407 cells. Finally, a possible hormonal control and modulation by the thiol-disulfide status of GSH transporter activity is suggested.
本研究首次对人肠上皮细胞系（I407）中的谷胱甘肽（GSH）特异性转运体进行了表征。GSH代谢对于肠道的抗氧化和解毒作用以及维持参与上皮细胞蛋白质活性调节机制的腔内硫醇 - 二硫键比率非常重要。GSH水平降低与肠道或其他器官的生理病理改变有关。在大鼠、小鼠和兔子的各种细胞类型的膜中已鉴定出GSH特异性转运系统。当细胞外摄取介质中的Na +被胆碱 +或K +取代时，GSH摄取时间进程的相似行为以及动力学饱和和对GSH预加载细胞中GSH摄取的反刺激作用证实了存在不依赖Na +的GSH转运系统。此外，当细胞外介质中存在阳离子时，该转运体被激活，并且它受膜电位变化的影响，当膜去极化发生时GSH摄取值增加。目前的结果还表明该转运体对GSH具有显著的亲和力和特异性；事实上，Km值非常低（90±20 microM），并且只有与GSH结构严格相关的化合物，如GSH S - 共轭物和GSH - 乙酯，才会抑制1407细胞中的GSH摄取。最后，提出了GSH转运体活性可能受激素控制以及受硫醇 - 二硫键状态调节的观点。
