Urinary 6β-Hydroxycortisol/Cortisol Ratios Measured by High-Performance Liquid Chromatography for Use as a Biomarker for the Human Cytochrome P-450 3A4

Lois Joellenbeck, Zheng Qian, Audrey Zarba, John D. Groopman

Research output: Contribution to journalArticlepeer-review

Abstract

Cortisol is metabolized to 6β-hydroxycortisol by the human cytochrome P-450 3A4, an enzyme implicated in the critical epoxidation reactions of aflatoxin B, and certain polycyclic aromatic hydrocarbons. A method has been developed to measure the 6β-hydroxycortisohcortisol ratio in human urine by reverse-phase high-performance liquid chromatography using diode-array detection. This method permits measurement of both Cortisols in a single chromatographic run and has the potential to measure other metabolites useful for the determination of other human cytochrome P-450 activities. Using the 6β-hydroxycortisol:cortisol ratio as a marker of cytochrome P-450 3A4 activity adjusts for the circadian fluctuation in Cortisol levels, providing a determination that is consistent over a 24-h period, obviating the need for 24-h urine collections. This high-performance liquid chromatography technique was used for the analysis of 14 different human urines and a range of ratios of 1.6 to 21.7 (mean ± SE, 6.2 ± 1.6) was found. These values are consistent with those reported in the literature. This method should be useful in molecular epidemiological studies investigating relationships between the susceptibility from environmental carcinogen exposure and cancer risk.

Original languageEnglish (US)
Pages (from-to)567-572
Number of pages6
JournalCancer Epidemiology Biomarkers and Prevention
Volume1
Issue number7
StatePublished - May 1 1992

ASJC Scopus subject areas

  • Epidemiology
  • Oncology

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