MECHANISM OF METHYLMERCURY EFFLUX FROM CULTURED ASTROCYTES
MECHANISM OF METHYLMERCURY EFFLUX FROM CULTURED ASTROCYTES
复制标题
DOI：
10.1016/0006-2952(94)90527-4
复制
发表时间：
1994-04-29
影响因子：
5.8
通讯作者：
YASUTAKE, A
中科院分区：
文献类型：
--
作者：
FUJIYAMA, J;HIRAYAMA, K;YASUTAKE, A
为研究甲基汞（MeHg）从中枢神经系统细胞中释放的机制，将培养的新生大鼠星形胶质细胞与10 μ M的MeHg-半胱氨酸（CySH）孵育30 min。介质中释放的甲基汞量接近一个平台水平（约1000克）。用CySH前体2-氧代噻唑烷-4-羧酸（OTC）处理细胞导致CySH和谷胱甘肽（GSH）的细胞水平显著增加。土霉素也增加了1.5倍的甲基汞流出负载细胞。另一种谷胱甘肽增强剂，谷胱甘肽异丙酯，也刺激甲基汞出口的细胞。离子交换柱层析，使用DEAE-Sephadex显示，甲基汞代谢产物，从而释放的专门甲基汞-GSH共轭物，无论有和没有OTC。由于甲基汞外排被丙磺舒的存在下显着抑制，外排发生通过丙磺舒敏感的有机酸转运系统。尽管用L-丁硫氨酸（S，R）-磺酰亚胺（BSO）处理后细胞内的GSH水平急剧下降，但仍检测到相当高水平（对照组的90%）的汞外排。由于在BSO处理的细胞的培养基中既没有检测到GSH-也没有检测到CySH-MeHg，GSH耗竭可能触发细胞中的一些其他分泌系统。这些结果表明，与GSH结合是大鼠星形胶质细胞中甲基汞外排的主要途径，并且细胞内GSH水平的升高可能是甲基汞中毒的合理治疗，促进甲基汞从关键组织中的加速消除。
To study the mechanism of methylmercury (MeHg) efflux from the central nervous system cells, cultured astroglia obtained from neonatal rats were incubated with 10 mu M MeHg-cysteine (CySH) for 30 min. After being washed four times, cells were incubated in Hg-free medium, and the release of MeHg from the cells was monitored. The amount of MeHg released in the medium approached a plateau level (ca. 31% of the loaded amount) at 4 hr. Treatment of the cells with a CySH precursor, 2-oxothiazolidine-4-carboxylic acid (OTC), resulted in a significant increase of cellular levels of CySH and glutathione (GSH). OTC also increased 1.5-fold the MeHg efflux from the loaded cells. Another GSH enhancer, GSH isopropyl ester, also stimulated MeHg export from the cells. Ion-exchange column chromatography using DEAE-Sephadex revealed that the MeHg metabolite thus released was exclusively MeHg-GSH conjugate, both with and without OTC. Since the MeHg efflux was suppressed significantly by the presence of probenecid, the efflux occurred via the probenecid-sensitive organic acid transport system. Even though the cellular GSH levels were depleted drastically by treatment with L-buthionine(S,R)-sulfoximine (BSO), a considerable level (90% of the control) of Hg efflux was detected. Since neither GSH- nor CySH-MeHg was detected in the culture medium of the BSO-treated cells, GSH depletion may trigger some other secretion system(s) in the cells. These results suggest that conjugation with GSH is the major pathway for MeHg efflux in rat astroglia, and that elevation in the cellular GSH level would possibly be a logical therapy for MeHg poisoning, promoting the accelerated elimination of MeHg from the critical tissues.