Intra-individual variation and sex differences in gene expression of cytochromes P450 in circulating leukocytes

Pharmacogenomics J. 2002;2(2):111-6. doi: 10.1038/sj.tpj.6500086.


To clarify partly inconsistent results in gene expression of cytochromes P450 (CYP) in the circulation, we undertook a systematic study over a long time period in 19 healthy men and women. CYP specific mRNA for 1A2, 1B1, 2E1 and 3A4 was studied in the leukocytes collected repeatedly on 20 occasions over a 10-week period. Our study revealed a varying pattern of CYP expression over time. CYP3A4 specific mRNA exhibited the largest intra-individual variation with an average coefficient of variation between 40 and 250%. CYP1B1 and CYP2E1 did not vary as much (39-110%). CYP1A2 was sporadically detected in only ten individuals, but varied considerably when measurable (61-256%). The expression in CYP1B1 was significantly higher in women than in men (P = 0.02). We conclude that CYP gene expression in blood varies considerably over time. It is conceivable that the variation reflects a hitherto unknown influence of exogenous or endogenous factors such as hormones, cytokines, and other circulating factors on the hematogeneous cytochromes.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Area Under Curve
  • Cytochrome P-450 Enzyme System / biosynthesis
  • Cytochrome P-450 Enzyme System / blood
  • Cytochrome P-450 Enzyme System / genetics*
  • Female
  • Gene Expression Regulation, Enzymologic / physiology*
  • Genetic Variation / physiology*
  • Humans
  • Leukocytes / enzymology*
  • Male
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / blood
  • RNA, Messenger / genetics
  • Sex Characteristics*
  • Statistics, Nonparametric


  • RNA, Messenger
  • Cytochrome P-450 Enzyme System