Protection of catechol oestrogen from oxidation during enzymic hydrolysis of biliary conjugates.
2-Hydroxyethynyloestradiol (2-OHEE2), a major biliary metabolite of 17 alpha-ethynyloestradiol in female rats, is conjugated largely with glucuronic acid. Accurate quantitation of [3H]2-OHEE2 deconjugated by enzymic hydrolysis depends upon co-incubation with ascorbate (5-10 mM). In the absence of ascorbate, the proportion of [3H]2-OHEE2 declines by 30 +/- 7% (x +/- SD, n = 4) during a 3 h incubation of bile with arylsulphohydrolase and beta-glucuronidase. Over 16 h, decomposition of the catechol leads to a decrease in ether-extractable 3H labelled components.
D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D001646:Bile / Q000032:analysis*; D004355:Drug Stability; D002393:Estrogens, Catechol / Q000032:analysis*; D004997:Ethinyl Estradiol / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism; D005188:False Negative Reactions; D005260:Female; D005966:Glucuronidase; D006868:Hydrolysis; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains
D002393:Estrogens, Catechol; D004997:Ethinyl Estradiol; C005933:2-hydroxyethynylestradiol; D005966:Glucuronidase; D001205:Ascorbic Acid