体外研究人细胞色素P450在雌二醇代谢中的作用(英文)

目的:研究雌二醇在cDNA表达的P450和人肝微粒体中的代谢机制,为在体内研究细胞色素P450活性与肿瘤发生的关系提供依据。方法:用HPLC-ECD法测定雌二醇的代谢产物。通过雌二醇在不同cDNA表达的P450中代谢,13例人肝微粒体中相关性研究,抑制剂对代谢的影响以及微粒体中17β-羟基脱氢化和2-羟基化代谢的催化动力学的研究来推断雌二醇的代谢机理。结果:在cDNA表达的P450中,催化2-羟基化代谢的P450按活性排列依次为CYP1A2、CYP3A4、CYP2C9。CYP2C9、CYP2C19和CYP2C8均具有较高的催化17β-羟基脱氢化活性。抑制CYP1A2与抑制CYP3A4对2-羟基化代谢产物生成的影响相似,可认为CYP1A2和CYP3A4在人肝微粒体中催化2-羟基化代谢的作用相近。雌二醇代谢的途径与底物浓度有关,低浓度时(1,10μmol/L)17β-羟基脱氢化为主要代谢途径;高浓度时(100μmol/L),2-羟基化成为主要代谢途径。结论:高底物浓度时,雌二醇主要由CYP1A2和CYP3A4催化代谢为2-羟基化产物。低底物浓度时,主要由CYP2C9、CYP2C19和CYP2C8催化生成17β-羟基去氢化产物。

Role of cytochrome P450 in estradiol metabolism in vitro

AIM: Catechol estrogens and 16alpha-hydroxy estrogen are important metabolites that cause carcinogenesis. This study was aimed to stud y the role of cytochrome P450 in estradiol metabolism. METHODS: The estradiol metabolites were determined with HPLC-ECD. Correlation of estradiol metabolites production between cytochrome P450 activity, the inhibitory effect of specific inhibitors and enzyme catalyzing kinetics were studied in cDNA-expressed P450 or human liver microsomes. RESULT: CYP1A2, CYP3A4, and CYP2C9 catalyze the estradiol 2-hydroxylation. CYP2C9, CYP2C19, and CYP2C8 have high activity in catalyzing 17beta-hydroxy dehydrogenation in cDNA expressed P450, but CYP1A2 is the most important enzyme in catalyzing estradiol 2-hydroxylation. Using furafyllin and troleandomycin to inhibit CYP1A2 and CYP3A4 in liver microsomes, it was found that the 2-hydroxylation had been inhibited about the same amount. This result suggests that in human liver microsomes CYP1A2 and CYP3A4 play an important role in 2-hydroxy estradiol formation. At low substrate concentration, 17beta -hydroxy dehydrogenation dominated the estradiol metabolism, but at high substrate concentration, 2-hydroxylation exceeded 17beta-hydroxy dehydrogenation to become the important mechanism. CONCLUSION: CYP1A2 and CYP3A4 are two important enzymes catalyzing the main estradiol 2-hydroxylation metabolism pathway at high substrate concentrations. 17beta-hydroxy dehydrogenation is the main metabolism pathway at low concentrations, and CYP2C9, CYP2C19, and CYP2C8 may have high catalyzing activity.