Razzouk C, McManus M E, Hayashi S, Schwartz D, Thorgeirsson S S
Biochem Pharmacol. 1985 May 1;34(9):1537-42. doi: 10.1016/0006-2952(85)90696-3.
The expression of epoxide hydrolases was studied in cultured rat hepatocytes and hepatoma cell lines. Styrene 7,8-oxide and benzo[a]pyrene 4,5-oxide were used as substrates for microsomal epoxide hydrolase and trans-stilbene oxide for the cytosolic form of this enzyme. In freshly isolated hepatocytes from control rats, microsomal epoxide hydrolase activity was 7.7 and 10.8 nmoles/mg cellular protein/min with benzo[a]pyrene 4,5-oxide and styrene 7,8-oxide as substrates respectively. This enzyme activity increased by more than 2-fold in hepatocytes after 24 hr in culture and remained elevated throughout 96 hr using both substrates. In cultured hepatocytes from rats pretreated in vivo with phenobarbital, trans-stilbene oxide, 2-acetylaminofluorene and N-hydroxy-2-acetylaminofluorene, both benzo[a]pyrene 4,5-oxide and styrene 7,8-oxide hydrolase activities were increased greater than 1.8 relative to controls. Hepatocytes from 2-acetylaminofluorene-pretreated animals at 24 hr in culture had approximately 9-fold higher activities than control hepatocytes. In marked contrast to microsomal epoxide hydrolase activity, the cytosolic enzyme showed an initial activity of 191 pmoles/mg cellular protein/min in freshly isolated hepatocytes, decreased by 75% after 24 hr in culture, and was barely detectable at 96 hr. A similar trend was apparent in hepatocytes from the pretreated animals. In vitro treatment of hepatocytes with trans-stilbene oxide and phenobarbital increased microsomal epoxide hydrolase, while this activity was refractory to 2-acetylaminofluorene treatment. Styrene 7,8-oxide hydrolase activity was increased in the McA-RH-7777 rat hepatoma cell line by phenobarbital, trans-stilbene oxide and 2-acetylaminofluorene treatment. Similarly, benzo[a]pyrene 4,5-oxide hydrolase activity was also increased in this cell line by treatment with phenobarbital and trans-stilbene oxide but not by 2-acetylaminofluorene. Microsomal epoxide hydrolase activity in rat H4-II-E hepatoma cells was refractory to induction, except by trans-stilbene oxide treatment, which caused a 70% increase in benzo[a]pyrene 4,5-oxide hydrolase activity.
在培养的大鼠肝细胞和肝癌细胞系中研究了环氧化物水解酶的表达。苯乙烯7,8 - 氧化物和苯并[a]芘4,5 - 氧化物用作微粒体环氧化物水解酶的底物，反式芪氧化物用作该酶胞质形式的底物。在来自对照大鼠的新鲜分离的肝细胞中，以苯并[a]芘4,5 - 氧化物和苯乙烯7,8 - 氧化物为底物时，微粒体环氧化物水解酶活性分别为7.7和10.8纳摩尔/毫克细胞蛋白/分钟。培养24小时后，肝细胞中该酶活性增加了2倍以上，并且在使用两种底物的整个96小时内都保持升高。在用苯巴比妥、反式芪氧化物、2 - 乙酰氨基芴和N - 羟基 - 2 - 乙酰氨基芴体内预处理的大鼠的培养肝细胞中，相对于对照，苯并[a]芘4,5 - 氧化物和苯乙烯7,8 - 氧化物水解酶活性均增加超过1.8倍。来自2 - 乙酰氨基芴预处理动物的肝细胞在培养24小时时的活性比对照肝细胞高约9倍。与微粒体环氧化物水解酶活性形成鲜明对比的是，胞质酶在新鲜分离的肝细胞中的初始活性为191皮摩尔/毫克细胞蛋白/分钟，培养24小时后降低了75%，在96小时时几乎检测不到。在预处理动物的肝细胞中也出现了类似的趋势。用反式芪氧化物和苯巴比妥体外处理肝细胞增加了微粒体环氧化物水解酶活性，而该活性对2 - 乙酰氨基芴处理无反应。在McA - RH - 7777大鼠肝癌细胞系中，苯巴比妥、反式芪氧化物和2 - 乙酰氨基芴处理增加了苯乙烯7,8 - 氧化物水解酶活性。同样，在该细胞系中，苯巴比妥和反式芪氧化物处理增加了苯并[a]芘4,5 - 氧化物水解酶活性，但2 - 乙酰氨基芴处理未增加。大鼠H4 - II - E肝癌细胞中的微粒体环氧化物水解酶活性除了用反式芪氧化物处理导致苯并[a]芘4,5 - 氧化物水解酶活性增加70%外，对诱导无反应。
