Makowska J M, Anders C, Goldfarb P S, Bonner F, Gibson G G
University of Surrey, Department of Biochemistry, Molecular Toxicology Group, Guildford, U.K.
Biochem Pharmacol. 1990 Sep 1;40(5):1083-93. doi: 10.1016/0006-2952(90)90497-9.
The influence of ciprofibrate, a potent oxyisobutyrate derivative, on several hepatic enzyme parameters was studied in five rat strains following a 14-day treatment period. Ciprofibrate-dependent hepatomegaly was observed at two dose levels (2 and 20 mg/kg) in all rat strains examined. A 10- to 15-fold induction in the 12-hydroxylation of lauric acid with a less marked 1.5- to 5-fold induction of 11-hydroxylation was observed in treated animals. This dose-dependent increase in fatty acid hydroxylase activity was associated with a maximal 10-fold increase in the specific content of cytochrome P-450 IVA1 isoenzyme apoprotein, as assessed immunochemically using an ELISA technique. The activities of the cytochrome P-450 I (IA1 and IA2) and II (IIB1 and IIB2) families, as measured by ethoxyresorufin-O-deethylase and benzphetamine-N-demethylase activities respectively, were decreased on treatment. In the mitochondria, monoamine oxidase activity was significantly decreased at the higher dose level whereas alpha-glycerophosphate dehydrogenase activity was elevated. Total carnitine acetyltransferase activity (mitochondrial and peroxisomal) and peroxisomal beta-oxidation were markedly increased at both dose levels in all strains examined. Cytosolic glutathione peroxidase activity, measured using both t-butylhydroperoxide and hydrogen peroxide as substrates, was decreased on treatment to approximately 50% of the control value. In treated animals, a marked increase in mRNA levels coding for cytochrome P-450 IVA1 and the peroxisomal bifunctional protein of the fatty acid beta-oxidation spiral was observed. However, mRNA levels coding for glutathione peroxidase appeared unchanged following ciprofibrate administration, in contrast to the above-noted decrease of glutathione peroxidase enzyme activity. Taken collectively, our results have further substantiated a close association between the induction of microsomal cytochrome P-450 IVA1, peroxisomal beta-oxidation and total carnitine acetyltransferase activity in rat liver, and have performed a conceptual basis for the rationalization of the chronic toxicity of peroxisome proliferators in this species.
在为期14天的治疗期后，研究了强效氧代异丁酸衍生物环丙贝特对五个大鼠品系几种肝酶参数的影响。在所检测的所有大鼠品系中，在两个剂量水平（2和20mg/kg）下均观察到环丙贝特依赖性肝肿大。在接受治疗的动物中，月桂酸12-羟化作用诱导了10至15倍，11-羟化作用诱导作用较弱，为1.5至5倍。脂肪酸羟化酶活性的这种剂量依赖性增加与细胞色素P-450 IVA1同工酶载脂蛋白的特定含量最大增加10倍相关，这是使用ELISA技术通过免疫化学评估的。分别通过乙氧基异吩恶唑酮-O-脱乙基酶和苄非他明-N-脱甲基酶活性测定的细胞色素P-450 I（IA1和IA2）和II（IIB1和IIB2）家族的活性在治疗后降低。在线粒体中，较高剂量水平下单胺氧化酶活性显著降低，而α-甘油磷酸脱氢酶活性升高。在所有检测的品系中，两个剂量水平下总肉碱乙酰转移酶活性（线粒体和过氧化物酶体）和过氧化物酶体β-氧化均显著增加。以叔丁基过氧化氢和过氧化氢为底物测定的胞质谷胱甘肽过氧化物酶活性在治疗后降低至对照值的约50%。在接受治疗的动物中，观察到编码细胞色素P-450 IVA1和脂肪酸β-氧化螺旋的过氧化物酶体双功能蛋白的mRNA水平显著增加。然而，与上述谷胱甘肽过氧化物酶活性降低相反，环丙贝特给药后编码谷胱甘肽过氧化物酶的mRNA水平似乎未发生变化。总体而言，我们的结果进一步证实了大鼠肝脏微粒体细胞色素P-450 IVA1的诱导、过氧化物酶体β-氧化和总肉碱乙酰转移酶活性之间的密切关联，并为该物种过氧化物酶体增殖剂的慢性毒性合理化提供了概念基础。
