Snawder J E, Lipscomb J C
Taft Laboratory, National Institute for Occupational Safety and Health, Cincinnati, Ohio 45226, USA.
Regul Toxicol Pharmacol. 2000 Oct;32(2):200-9. doi: 10.1006/rtph.2000.1424.
Differences in biotransformation activities may alter the bioavailability or efficacy of drugs, provide protection from certain xenobiotic and environmental agents, or increase toxicity of others. Cytochrome P450 (CYP450) enzymes are responsible for the majority of oxidation reactions of drugs and other xenobiotics and differences in their expression may directly produce interindividual differences in susceptibility to compounds whose toxicity is modulated by these enzymes. To rapidly quantify CYP450 forms in human hepatic microsomes, we developed, and applied, an ELISA to 40 samples of microsomes from adult human organ donors. The procedure was reliable and the results were reproducible within normal limits. Protein content for CYP1A, CYP2E1, and CYP3A positively correlated with suitable marker activities. CYP1A, CYP2B, CYP2C6, CYP2C11, CYP2E1, and CYP3A protein content demonstrated 36-, 13-, 11-, 2-, 12-, and 22-fold differences between the highest and lowest samples and the values were normally distributed. Of the forms examined, CYP3A was expressed in the highest amount and it was the only form whose content was correlated with total CYP450 content. Content of other forms was independent of total CYP450. We further determined the contribution of specific forms to the biotransformation of trichloroethylene as a model substrate. CYP2E1 was strongly correlated with chloral hydrate formation from trichloroethylene; CYP2B displayed the strongest correlation with trichloroethanol formation. These data describing the expression and distribution of these forms in human microsomes can be used to extrapolate in vitro derived metabolic rates for toxicologically important reactions, when form selectivity and specific activity are known. This approach may be applied to refine estimates of human interindividual differences in susceptibility for application in human health risk assessment.
生物转化活性的差异可能会改变药物的生物利用度或疗效，提供对某些外源性物质和环境因子的保护，或增加其他物质的毒性。细胞色素P450（CYP450）酶负责大多数药物和其他外源性物质的氧化反应，其表达差异可能直接导致个体对由这些酶调节毒性的化合物的易感性产生个体差异。为了快速定量人肝微粒体中的CYP450形式，我们开发并应用了一种酶联免疫吸附测定法（ELISA）检测40份来自成年人体器官供体的微粒体样本。该方法可靠，结果在正常范围内可重复。CYP1A、CYP2E1和CYP3A的蛋白含量与合适的标记活性呈正相关。CYP1A、CYP2B、CYP2C6、CYP2C11、CYP2E1和CYP3A的蛋白含量在最高和最低样本之间显示出36倍、13倍、11倍、2倍、12倍和22倍的差异，且这些值呈正态分布。在所检测的形式中，CYP3A表达量最高，并且它是唯一其含量与总CYP450含量相关的形式。其他形式的含量与总CYP450无关。我们进一步确定了特定形式对作为模型底物的三氯乙烯生物转化的贡献。CYP2E1与三氯乙烯形成水合氯醛的过程密切相关；CYP2B与三氯乙醇形成的相关性最强。当形式选择性和比活性已知时，这些描述这些形式在人微粒体中的表达和分布的数据可用于推断体外得出的毒理学重要反应的代谢率。这种方法可用于完善对人类个体易感性差异的估计，以应用于人类健康风险评估。
