Milton M N, Elcombe C R, Gibson G G
University of Surrey, Department of Biochemistry, Guildford, UK.
Biochem Pharmacol. 1990 Dec 15;40(12):2727-32. doi: 10.1016/0006-2952(90)90594-b.
The time course of induction of microsomal and peroxisomal lipid-metabolizing enzymes in male Wistar rat liver has been investigated following a single i.p. dose of clofibrate (250 mg/kg). The microsomal enzyme, cytochrome P450IVA1, demonstrated a biphasic response to sodium clofibrate administration, the biphasic response consisting of an initial small response, peaking at approximately 30 min post-dose and returning to near baseline values after 2 hr. A second major induction of cytochrome P450IVA1 occurred between 18 and 24 hr post-dose. This biphasic phenomenon for cytochrome P450IVA1 was observed for the enzyme activity (lauric acid hydroxylase), immunodetectable protein (using a specific ELISA method) and at the mRNA level (using a 2.1 kilobase cytochrome P450IVA1 cDNA probe). In contrast, peroxisomal fatty acid beta-oxidation enzymes responded in a monophasic manner to clofibrate administration, peaking approximately 24 hr post-dose. Accordingly, microsomal cytochrome P450IVA1 was induced before the peroxisomal enzymes of fatty acid beta-oxidation. The effect of cycloheximide on the induction of peroxisome proliferation by clofibrate was additionally investigated. The prior administration of cycloheximide to Wistar rats ablated the clofibrate-dependent induction of both cytochrome P450IVA1 and peroxisomal-dependent lipid metabolism and also blocked the corresponding synthesis of enzyme proteins. Cycloheximide additionally inhibited the clofibrate-dependent increase in peroxisomal acyl-CoA oxidase mRNA, but was without effect on the induced cytochrome P450IVA1 mRNA levels, indicating a protein or enzyme dependency for the phenomenon of peroxisome proliferation. Taken collectively, our data strongly argues that the regulation of microsomal cytochrome P450IVA1 and peroxisomal fatty acid beta-oxidation enzymes are closely related, possibly through the initial, clofibrate-dependent regulation of cytochrome P450IVA1.
在雄性Wistar大鼠腹腔注射一剂氯贝丁酯（250mg/kg）后，对其肝脏中微粒体和过氧化物酶体脂质代谢酶的诱导时间进程进行了研究。微粒体酶细胞色素P450IVA1对氯贝丁酯给药表现出双相反应，该双相反应包括最初的小反应，在给药后约30分钟达到峰值，并在2小时后恢复到接近基线值。细胞色素P450IVA1的第二次主要诱导发生在给药后18至24小时。细胞色素P450IVA1的这种双相现象在酶活性（月桂酸羟化酶）、免疫可检测蛋白（使用特异性ELISA方法）和mRNA水平（使用2.1千碱基细胞色素P450IVA1 cDNA探针）上均有观察到。相比之下，过氧化物酶体脂肪酸β-氧化酶对氯贝丁酯给药的反应呈单相，在给药后约24小时达到峰值。因此，微粒体细胞色素P450IVA1在脂肪酸β-氧化的过氧化物酶体酶之前被诱导。此外，还研究了环己酰亚胺对氯贝丁酯诱导过氧化物酶体增殖的影响。预先给Wistar大鼠注射环己酰亚胺消除了氯贝丁酯依赖性的细胞色素P450IVA1诱导和过氧化物酶体依赖性脂质代谢，并且还阻断了相应酶蛋白的合成。环己酰亚胺还抑制了氯贝丁酯依赖性的过氧化物酶体酰基辅酶A氧化酶mRNA增加，但对诱导的细胞色素P450IVA1 mRNA水平没有影响，表明过氧化物酶体增殖现象存在蛋白质或酶依赖性。总体而言，我们的数据有力地表明，微粒体细胞色素P450IVA1和过氧化物酶体脂肪酸β-氧化酶的调节密切相关，可能是通过细胞色素P450IVA1的最初氯贝丁酯依赖性调节。
