Polhuijs M, Lankhaar G, Mulder G J
Division of Toxicology, University of Leiden, The Netherlands.
Biochem J. 1992 Jul 15;285 ( Pt 2)(Pt 2):401-4. doi: 10.1042/bj2850401.
The relationship between hepatic glutathione content and hepatic glutathione conjugation rate in the rat in vivo was investigated. As substrate for glutathione conjugation, racemic (R,S)-2-bromoisovalerylurea (BIU) was used which gives rise to the biliary excretion of two diastereoisomeric glutathione conjugates and the urinary excretion of two diastereoisomeric mercapturates. The excretion rate of the glutathione conjugate in bile reflects hepatic conjugation exclusively. An intravenous infusion of BIU was given and the excretion rates of the metabolites in bile and urine were determined. The glutathione concentration in the liver was followed by taking biopsies every hour. Glutathione was depleted by the infused substrate; in rats that were pretreated with the inhibitor of glutathione biosynthesis, buthionine sulphoximine (BSO), the depletion of the glutathione content was more rapid. The rate of excretion of the glutathione conjugate in bile was plotted against hepatic glutathione content. These results indicate that the 'organ Km' for glutathione in the liver is approximately 0.5 mumol/g of liver, so that the hepatic glutathione conjugation rate is decreased only at severe glutathione depletion.
研究了大鼠体内肝脏谷胱甘肽含量与肝脏谷胱甘肽结合率之间的关系。作为谷胱甘肽结合的底物，使用了外消旋（R,S）-2-溴异戊酰脲（BIU），它会导致两种非对映体谷胱甘肽结合物经胆汁排泄，以及两种非对映体硫醚氨酸经尿液排泄。胆汁中谷胱甘肽结合物的排泄率仅反映肝脏的结合情况。静脉输注BIU，并测定胆汁和尿液中代谢物的排泄率。每小时取活检组织以跟踪肝脏中的谷胱甘肽浓度。输注底物会使谷胱甘肽耗竭；在用谷胱甘肽生物合成抑制剂丁硫氨酸亚砜胺（BSO）预处理的大鼠中，谷胱甘肽含量的耗竭更快。将胆汁中谷胱甘肽结合物的排泄率与肝脏谷胱甘肽含量作图。这些结果表明，肝脏中谷胱甘肽的“器官Km”约为0.5 μmol/g肝脏，因此只有在严重的谷胱甘肽耗竭时肝脏谷胱甘肽结合率才会降低。
