DuTeaux Shelley Brown, Newman John W, Morisseau Christophe, Fairbairn Elise A, Jelks Karen, Hammock Bruce D, Miller Marion G
Department of Environmental Toxicology, University of California-Davis, Davis, California 95616, USA.
Toxicol Sci. 2004 Apr;78(2):187-95. doi: 10.1093/toxsci/kfh066. Epub 2004 Jan 21.
Epoxide hydrolases play an important role in detoxifying epoxides that arise from the metabolism of xenobiotic and endogenous compounds. Both the soluble and microsomal forms of epoxide hydrolase (sEH and mEH, respectively) have been detected in the rat testis. Because of the important role the epididymis plays in sperm maturation and protection, the present study evaluated the presence and activity of these two epoxide hydrolases in the rat epididymis. Using Western blotting, protein bands consistent in size with both mEH and sEH were detected in the caput, corpus, and cauda of the epididymis. The mEH immunoreactive bands in the epididymis ( approximately 50 kDa) were consistent with mEH detected in the liver and kidney. The sEH immunoreactive bands in the epididymis ( approximately 65 kDa) were consistent with a recombinant sEH standard and sEH detected in the liver, kidney, and testis. The presence of mEH and sEH in the epididymis was supported by observations from substrate-based enzyme assays. Results indicated that epididymal mEH can hydrolyze [(3)H]-cis-stilbene oxide to the corresponding diol at levels approximately 9% of the kidney. Epididymal sEH hydrolyzed the substrate [(3)H]-trans-diphenylpropene oxide to the corresponding diol and this activity was inhibited by cyclohexyl-dodecyl urea. Arachidonic acid epoxygenase activity was detected in epididymal S9 fractions, suggesting that fatty acid metabolism by epididymal cytochrome P450s can form epoxides that subsequently become substrates for epididymal sEH. Results from the present study indicate that the epididymis contains at least two active forms of epoxide hydrolase. The role of these enzymes in the detoxification of xenobiotic epoxides is well known, although it is unclear what cellular role they may play in the formation of biologically active metabolites in the epididymis.
环氧化物水解酶在使外源性和内源性化合物代谢产生的环氧化物解毒过程中发挥着重要作用。在大鼠睾丸中已检测到环氧化物水解酶的可溶性和微粒体形式（分别为可溶性环氧化物水解酶和微粒体环氧化物水解酶）。由于附睾在精子成熟和保护过程中发挥着重要作用，本研究评估了这两种环氧化物水解酶在大鼠附睾中的存在情况和活性。通过蛋白质免疫印迹法，在附睾的头部、体部和尾部检测到了大小与微粒体环氧化物水解酶和可溶性环氧化物水解酶一致的蛋白条带。附睾中微粒体环氧化物水解酶的免疫反应条带（约50 kDa）与在肝脏和肾脏中检测到的微粒体环氧化物水解酶一致。附睾中可溶性环氧化物水解酶的免疫反应条带（约65 kDa）与重组可溶性环氧化物水解酶标准品以及在肝脏、肾脏和睾丸中检测到的可溶性环氧化物水解酶一致。基于底物的酶活性测定结果也证实了附睾中存在微粒体环氧化物水解酶和可溶性环氧化物水解酶。结果表明，附睾微粒体环氧化物水解酶能够将[³H]-顺式二苯乙烯氧化物水解为相应的二醇，其水解水平约为肾脏的9%。附睾可溶性环氧化物水解酶将底物[³H]-反式二苯丙烯氧化物水解为相应的二醇，且该活性受到环己基十二烷基脲的抑制。在附睾S9组分中检测到了花生四烯酸环氧合酶活性，这表明附睾细胞色素P450s介导的脂肪酸代谢能够形成环氧化物，随后这些环氧化物成为附睾可溶性环氧化物水解酶的底物。本研究结果表明，附睾中至少含有两种活性形式的环氧化物水解酶。这些酶在外源性环氧化物解毒中的作用已为人熟知，尽管尚不清楚它们在附睾中生物活性代谢物形成过程中可能发挥的细胞作用。
