Individual Difference in Drug Metabolism and Disposition : Toxicological Significance of Genotypes and Phenotypes of S-mephenytoin 4'-hydroxylase(CYP2C19)

s -甲苯妥英的4'-羟基化已被证明是由CYP2C19介导的。它在一些相关的氢妥英和巴比妥酸盐的代谢中也很重要，在结构不同的药物如奥美拉唑、普罗胍和西酞普兰的代谢中也很重要。因此，在这些药物的处置中会出现很大的表型间差异，这可能会影响它们的毒性和疗效。因此，我们检测CYP2C19基因多态性与奥美拉唑代谢的关系，以评估中毒严重程度并预测中毒结果，为法医和临床毒理学提供依据。本研究从无血缘关系的健康日本人血液中提取DNA样本，建立了一种基于限制性内切片段长度多态性的快速、简单的基因分型方法。使用de Morais等人描述的等位基因特异性引物进行轻微修改，通过PCR扩增进行CYP2C19基因分型鉴定。PCR产物用限制性内切酶酶切，聚丙烯酰胺凝胶电泳分析。此外，通过测量奥美拉唑和羟奥美拉唑在血清中的浓度来确定CYP2C19的表型，在奥美拉唑摄入后2小时采集，采用Marinac等人描述的高效液相色谱法进行了轻微修改。因此，观察到的基因型为CYP2C19^*1A（野生型：wt）， CYP2C19^*2 （m1）和CYP2C19^*3 （m2）。野生型奥美拉唑羟基化指数为-1.15，异源型为-0.78，同源突变型为1.22。CYP2C19基因型与表型相关。这些结果表明，药物代谢酶基因分型分析在法医和临床毒理学评估中毒严重程度和预测结果方面将发挥更重要的作用。

The 4'-hydroxylation of S-mephenytoin has been shown to be mediated by CYP2C19. It is also important in the metabolism of a number of relatd hydantoins and barbiturates, as well as in that of structurally dissimilar drugs such as omeprazole, proguanil, and citalopram. As a result, large interphenotypic differences occur in the disposition of these drugs, which may affect their toxicity and efficacy.Therefore, we examined the relationship between genetic polymorphism of CYP2C19 and metabolism of omeprazole in order to assess the severity and to predict the outcome of poisoning for the forensic and clinical toxicology. In this study, we prepared the DNA samples from the blood of unrelated healthy Japanese, and developed a rapid and simple genotyping method using a polymerase chain reaction (PCR) based restriction fragment length polymorphism. Genotyping procedures for the identification of CYP2C19 were performed by PCR amplification with use of the allele-specific primers described by de Morais et al. with minor modifications. PCR products were digested with the restriction enzymes, and were analyzed by polyacrylamide gel electrophoresis. Furthermore, CYP2C19 phenotypes were determined by measuring omeprazole and hydroxyomeprazole concentrations in the serum, collected at 2 hours after omeprazole ingestion, by high performance liquid chromatography described by Marinac et al. with minor modifications. Consequently, the genotypes observed were CYP2C19^*1A (wild type : wt), CYP2C19^*2 (m1), and CYP2C19^*3 (m2). The omeprazole hydroxylation index of wild-type was -1.15, whereas hetero-type was -0.78, and homo-mutated type 1.22. The genotype of CYP2C19 correlated with the phenotype. These results proved that genotyping assays of drug metabolizing enzymes would play more important role in assessing the severity and predicting the outcome of poisoning for forensic and clinical toxicology.