Snel C A, Pang K S, Mulder G J
Division of Toxicology, Leiden/Amsterdam Center for Drug Research, Leiden University, The Netherlands.
Hepatology. 1995 May;21(5):1387-94. doi: 10.1016/0270-9139(95)90061-6.
The relation between the rate of glutathione (GSH) conjugation and hepatic GSH content was studied in the rat in vivo and the in situ single-pass-perfused rat liver preparation with bromosulfophthalein (BSP) as the model substrate. The biliary excretion of the BSP-GSH conjugate and the hepatic GSH content were monitored simultaneously during intravenous infusions with BSP in the rat in vivo, and during liver perfusions with BSP-containing perfusion medium. Rats were pretreated with single or multiple doses of buthionine sulfoximine, an inhibitor of the de novo synthesis of GSH. Surprisingly, the excretion of the BSP-GSH conjugate was sustained at a high rate, despite a virtually complete depletion of hepatic GSH, both in the rat in vivo as well as in the perfused rat liver. The results indicate that GSH was still available for conjugation with BSP after apparent depletion of the hepatic GSH pool, presumably because of a residual de novo synthesis of GSH in the liver. Despite the multiple pretreatment with buthionine sulfoximine, the de novo GSH synthesis was sufficient to sustain a high rate of GSH conjugation of BSP. The cosubstrate-Km for GSH conjugation of BSP in the liver was estimated to be very small (approximately 0.3 mumol/g): the excretion rate of the BSP-GSH conjugate was only impaired at minimal hepatic GSH levels.
以溴磺酞钠（BSP）作为模型底物，在大鼠体内及原位单通道灌注大鼠肝脏标本中研究了谷胱甘肽（GSH）结合速率与肝脏GSH含量之间的关系。在大鼠体内静脉输注BSP期间以及用含BSP的灌注介质进行肝脏灌注期间，同时监测BSP-GSH结合物的胆汁排泄和肝脏GSH含量。用单剂量或多剂量的丁硫氨酸亚砜胺（一种GSH从头合成抑制剂）对大鼠进行预处理。令人惊讶的是，尽管在大鼠体内以及灌注的大鼠肝脏中肝脏GSH几乎完全耗尽，但BSP-GSH结合物的排泄仍以高速率持续进行。结果表明，在肝脏GSH池明显耗尽后，GSH仍可用于与BSP结合，推测这是由于肝脏中GSH的残余从头合成。尽管用丁硫氨酸亚砜胺进行了多次预处理，但GSH的从头合成足以维持BSP的GSH结合的高速率。估计肝脏中BSP的GSH结合的共底物-Km非常小（约0.3 μmol/g）：仅在肝脏GSH水平最低时，BSP-GSH结合物的排泄速率才会受损。
