Phagocytosis and oxidative burst: reference values for flow cytometric assays independent of age.

Rebbeck et al. (7) for US Caucasians. In that specific study on 94 healthy volunteers, 3.2% appeared to be homozygous for this mutation. We did not find any CYP3A4-V homozygotes among the 199 individuals studied. The allele and genotype frequencies were in Hardy-Weinberg equilibrium (P ϭ 0.432); the absence of ho-mozygotes in our study population of 199 individuals is consistent with a Hardy-Weinberg distribution. In Swed-ish Caucasians, 3 CYP3A4-V alleles were found recently among 39 individuals studied, giving an allelic frequency of 3.8% (15), whereas Sata et al. (9) reported an allelic frequency of 4.2% in 59 white subjects. These data are more in agreement with our results. CYP3A4 is the most abundant form of the cytochrome P450 enzyme family present in human liver and is involved in the metabolism of many drugs (3, 4, 16). The recently described A(Ϫ290)G genetic polymorphism in the 5Ј regulatory region potentially alters the transcription efficiency and thus the overall enzymatic activity of CYP3A4. Initially, the effect of this mutation on transcription was believed to be a decrease, based on the clinical presentation of prostate cancer (7) and drug-induced leukemia (12). Later experiments, in which protein expression and enzymatic activity in liver samples were compared, suggested that the CYP3A4-V mutation had no effect on transcription (14). This was supported by experiments on the 6␤-hydroxylation of testosterone in three microsomal liver samples from individuals heterozygous for the CYP3A4-V allele (15), although this conclusion was later questioned by others (17). Experiments in which the promoter region of CYP3A4 was fused to the lucif-erase reporter gene, followed by expression of these constructs in HepG2 and MCF7 cells, indicated that the CYP3A4-V polymorphism increases CYP3A4 transcription compared with the CYP3A4 wild-type allele (18). Further studies are needed to show that the CYP3A4-V polymorphism will lead to increased CYP3A4 enzymatic activity not only in cell culture systems but also in individuals. In conclusion, we have described and validated a fast and simple PCR-RFLP analysis that can be applied for specific screening for the CYP3A4-V allele. This assay could greatly facilitate studies on the effect of this poly-morphism in endogenous processes, environmental susceptibility to cancer, and individual ability to metabolize drugs. variations in human liver cytochrome P-450 enzymes involved in the oxidation of drugs, carcinogens and toxic chemicals: studies with liver micro-somes of 30 Japanese and 30 Caucasians. Use of midazolam as a human cytochrome P450 3A probe. I. In …