Increase in urinary excretion of 6β-hydroxycortisol in common marmosets as a marker of hepatic CYP3A induction

Abstract

The ratio of urinary 6beta-hydroxycortisol (6beta-OHF) to free cortisol (F), i.e., the 6beta-OHF/F ratio, has been reported to be a specific marker for human CYP3A induction by in vivo studies of human subjects. In the development of drugs, it is quite beneficial to predict human CYP3A induction in preclinical safety studies using urine samples from experimental animals. We examined the 6beta-OHF/F ratio in urine of common marmosets administered with rifampicin, a potent inducer of CYP3A, to evaluate the usefulness of common marmosets for the prediction of CYP3A induction. Rifampicin was orally administered to three groups of four male common marmosets at doses of 0, 10, and 20 mg/kg per day for 4 days. Amounts of 6beta-OHF and F in urine samples were determined by means of high-performance liquid chromatography (HPLC) during the experimental period. One day after the 4th dosing, animals were killed, and P450 contents and P450-catalyzed. 7-alkoxycoumarin O-dealkylase (ACD) activities in the liver were measured. Western blot analysis of liver microsomes was also performed using anti-rat P450 (CYP1A1, 2B1/2, 3A, and 4A) antibodies. The results indicated elevations in the 6beta-OHF/F ratios that were dependent on both the dosing period and dose levels adopted. The ratios on day 4 reached 4.7- and 5.3-fold the pre-administration values in the 10 and 20 mg/kg per day groups, respectively. P450 contents and ACD activities were also elevated in all of the groups. Western blot analysis showed specific increases in the protein which cross-reacts with anti-rat CYP3A antibody in all of the groups. Furthermore, the 6beta-OHF/F ratio was well correlated with the CYP3A contents in liver (r = 0.906). These results indicated that increase in urinary excretion of 6beta-OHF is a specific marker of the induction of hepatic CYP3A in common marmosets just as in humans. Consequently, the present study suggested that human CYP3A induction elicited by chemical agents can be predicted in common marmosets by measuring the urinary excretion of 6beta-OHF.

Effects of Plasmodium falciparum infection on the pharmacokinetics of quinine and its metabolites in pregnant and non-pregnant Sudanese women

“…Cytochrome P450 3A4 is the major drug metabolising enzyme [25], which catalyses the biotransformation of quinine to 3-hydroxyquinine. A known marker for induction of hepatic cytochrome P450 3A4 is 6β-hydroxycortisol formation [26][27][28][29]. Using this marker studies performed in pregnant women have shown a significant increase in the formation of this metabolite during pregnancy in comparison to postpartum [30] indicating higher activity of CYP3A.…”

Comprehensive study of urinary cortisol metabolites in hyperthyroid and hypothyroid patients

“…The enzyme is expressed along with the glucocorticoid receptor (GR), and thereby regulates glucocorticoid (GC) activity. Substantial amounts of 11β‐HSD1 are found in the human liver, adipose tissue, gonad, brain, pituitary and vascular smooth muscle 3–5 . 11β‐HSD type 2 (11β‐HSD2) is found in the same organs as the mineralocorticoid receptor (MR).…”

“…The enzyme 6β‐hydroxylase is also responsible for cortisol metabolism, albeit only for a very small part of it (an estimated 1% of the overall cortisol metabolism) 1 . Through this pathway, cortisol is excreted into the urine in the form of 6β‐hydroxycortisol (6β‐OHF), a metabolite also used as an index of the activity of cytochrome P450 (CYP) 3A4 in the liver 4,10 . In addition, some cortisol (F) and cortisone (E) is excreted into the urine without prior metabolism.…”

“…Urinary 17‐hydroxycorticosteroid (17‐OHCS) has long been known to reflect all the fractions of the corticosteroids, possessing a hydroxyl group at position 17 of the steroid structure; that is, THF, THE, allo‐THF, 6β‐OHF, F and E 1,11 . Reports on hyperthyroid subjects have described an enhanced reduction of the A‐ring double bond of the steroid structure (C4–5) and increased 11β‐HSD activity 3–9,12 . Several earlier reports have also asserted that altered thyroid states influence urinary 6β‐OHF 11,13,14 .…”