Standeven A M, Wetterhahn K E
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire.
Toxicol Appl Pharmacol. 1991 Feb;107(2):269-84. doi: 10.1016/0041-008x(91)90208-v.
L-Buthionine-S,R-sulfoximine (BSO), a potent inhibitor of gamma-glutamylcysteine synthetase, is commonly used as an experimental tool for the specific depletion of glutathione. Since cysteine is a key precursor for glutathione biosynthesis, we investigated the possibility that BSO might also affect the free cysteine pool in rat liver and kidney tissues in vivo. Male CD(SD)BR rats (150-200 g) were injected ip with various doses of BSO (0.25-4.0 mmol/kg), and glutathione and cysteine were measured in liver and kidney using HPLC with electrochemical detection and/or spectroscopic techniques. No hepatotoxicity or nephrotoxicity was observed at the highest BSO dose (4.0 mmol/kg) used. BSO caused the expected decreases of hepatic and renal glutathione at all doses, although glutathione depletion was more rapid, was achieved at a lower BSO dose, and was more sustained in kidney than in liver. Hepatic cysteine levels nearly doubled 20 min after BSO treatment (1.0 mmol/kg, ip), but were not significantly different from control at later time points. In contrast, renal cysteine was significantly depleted from 20 min to 25 hr postinjection with a time course closely paralleling that of renal glutathione depletion. These changes are discussed in the context of models for inter- and intraorgan transport of glutathione and cysteine. We also provide evidence that an artifact, most likely the gamma-glutamyltranspeptidase (GGT)-initiated breakdown of glutathione, leads to a rapid postmortem increase of cysteine levels in liver and particularly in kidney of rats. Simultaneous decreases in GSH levels can be demonstrated in kidney. This artifact needs to be minimized in toxicological studies of glutathione and cysteine in kidney and other GGT-rich organs, as the measured levels of these thiols may not reflect the true concentrations occurring in vivo.
L-丁硫氨酸-S，R-亚砜亚胺（BSO）是γ-谷氨酰半胱氨酸合成酶的强效抑制剂，常用作特异性消耗谷胱甘肽的实验工具。由于半胱氨酸是谷胱甘肽生物合成的关键前体，我们研究了BSO在体内可能影响大鼠肝脏和肾脏组织中游离半胱氨酸池的可能性。雄性CD(SD)BR大鼠（150 - 200 g）腹腔注射不同剂量的BSO（0.25 - 4.0 mmol/kg），使用高效液相色谱-电化学检测和/或光谱技术测定肝脏和肾脏中的谷胱甘肽和半胱氨酸。在所使用的最高BSO剂量（4.0 mmol/kg）下未观察到肝毒性或肾毒性。所有剂量的BSO均导致肝脏和肾脏中谷胱甘肽预期的降低，尽管谷胱甘肽消耗更快，在较低的BSO剂量下即可实现，并且在肾脏中比在肝脏中更持久。BSO处理（1.0 mmol/kg，腹腔注射）20分钟后肝脏半胱氨酸水平几乎翻倍，但在随后的时间点与对照组无显著差异。相比之下，肾脏半胱氨酸在注射后20分钟至25小时显著减少，其时间进程与肾脏谷胱甘肽消耗密切平行。在谷胱甘肽和半胱氨酸的器官间和器官内转运模型的背景下讨论了这些变化。我们还提供证据表明，一种假象（最可能是γ-谷氨酰转肽酶（GGT）引发的谷胱甘肽分解）导致大鼠肝脏尤其是肾脏中半胱氨酸水平在死后迅速升高。同时可以证明肾脏中谷胱甘肽水平降低。在肾脏和其他富含GGT的器官中进行谷胱甘肽和半胱氨酸的毒理学研究时，需要尽量减少这种假象，因为这些硫醇的测量水平可能无法反映体内真实浓度。
