Bains S K, Gardiner S M, Mannweiler K, Gillett D, Gibson G G
Biochem Pharmacol. 1985 Sep 15;34(18):3221-9. doi: 10.1016/0006-2952(85)90338-7.
The influence of four hypolipidaemic drugs (clofibrate, WY-14,643, clobuzarit and bezafibrate) on hepatic cytochrome P-450 and fatty acid metabolism in male rat liver microsomes has been investigated. All of the hypolipidaemic drugs tested significantly induced the hydroxylation of lauric acid and, furthermore, this was accompanied by a concomitant 3-fold induction of a specific isoenzyme of cytochrome P-450 (termed cytochrome P-452) as determined by a single radial immunodiffusion technique. In addition, immunochemical quantitation of cytochrome P-452 in control, uninduced rat liver microsomes revealed that this particular isoenzyme constituted 22% of the total carbon monoxide-discernible cytochrome P-450 population. This has led us to the conclusion that cytochrome P-452 is a constitutive cytochrome P-450 isoenzyme and therefore that hypolipidaemic agents function as inducers of constitutive haemoprotein isoenzymes. Cytochrome P-452 plays a significant role in the hydroxylation of lauric acid as evidenced by inhibition of hydroxylase activity in the presence of an anti-P-452 IgG fraction. In addition, this antibody preferentially inhibits the 12-hydroxylation of lauric acid in rat liver microsomes by comparison to the 11-hydroxylase activity. Our studies have also shown that arachidonic acid serves as an excellent substrate for hypolipidaemic-induced cytochrome P-452, resulting in the formation of several metabolites that have been separated by reverse phase HPLC. Furthermore, a specific metabolite (or group of metabolites) of arachidonic acid is induced by clofibrate pretreatment and that the formation of this metabolite(s) is inhibited by an antibody to cytochrome P-452. By comparison, other metabolites of arachidonic acid remain refractory to induction by clofibrate and are not inhibited by the presence of anti-P-452 IgG. In addition, a reconstituted enzyme system containing highly purified cytochrome P-452 actively catalyses the above specific oxidation of arachidonic acid, a reaction that is significantly stimulated by the presence of cytochrome b5. Taken collectively, our data provide compelling evidence that hypolipidaemic agents induce a specific isoenzyme of hepatic microsomal P-450 that readily oxidizes fatty acids and that arachidonic acid may serve as an excellent endogenous substrate for this novel haemoprotein.
研究了四种降血脂药物（氯贝丁酯、WY - 14,643、氯布扎利特和苯扎贝特）对雄性大鼠肝微粒体中肝细胞色素P - 450及脂肪酸代谢的影响。所有受试降血脂药物均显著诱导了月桂酸的羟化作用，此外，通过单向放射免疫扩散技术测定，这伴随着细胞色素P - 450的一种特定同工酶（称为细胞色素P - 452）3倍的诱导。此外，对对照未诱导的大鼠肝微粒体中细胞色素P - 452进行免疫化学定量分析发现，这种特定同工酶占可被一氧化碳识别的细胞色素P - 450总量的22%。由此我们得出结论，细胞色素P - 452是一种组成型细胞色素P - 450同工酶，因此降血脂药物可作为组成型血红蛋白同工酶的诱导剂。细胞色素P - 452在月桂酸的羟化过程中起重要作用，这在存在抗P - 452 IgG组分时羟化酶活性受到抑制中得到证明。此外，与11 - 羟化酶活性相比，该抗体优先抑制大鼠肝微粒体中月桂酸的12 - 羟化作用。我们的研究还表明，花生四烯酸是降血脂诱导的细胞色素P - 452的良好底物，可形成几种已通过反相高效液相色谱分离的代谢产物。此外，氯贝丁酯预处理可诱导花生四烯酸的一种特定代谢产物（或一组代谢产物），且该代谢产物的形成受到细胞色素P - 452抗体的抑制。相比之下，花生四烯酸的其他代谢产物对氯贝丁酯的诱导不敏感，且不受抗P - 452 IgG的抑制。此外，含有高度纯化细胞色素P - 452的重组酶系统可积极催化上述花生四烯酸的特定氧化反应，该反应在细胞色素b5存在时受到显著刺激。综合来看，我们的数据提供了令人信服的证据，即降血脂药物诱导肝微粒体P - 450的一种特定同工酶，该同工酶能轻易氧化脂肪酸，且花生四烯酸可能是这种新型血红蛋白的良好内源性底物。
