4-Hydroxyestradiol is conjugated with thiols primarily at C-2: evidence from regiospecific displacement of tritium by rat liver microsomes or tyrosinase
4-Hydroxyestradiol bearing a 3H label specifically at C-2 was prepared chemically and incubated with male rat liver microsomes or mushroom tyrosinase. A very high proportion (80-90%) of the 3H was displaced from the labeled steroid when either glutathione or N-acetylcysteine was present, and tyrosinase was shown not to require NADPH as cofactor for this reaction. In either case, only negligible amounts (less than 3%) of the 3H radioactivity were found associated with water-soluble adducts in contrast to 3H-labeled 2-hydroxyestradiol, which gave rise to about 25% of such products. The effect of ascorbic acid on the microsomal reaction with regiospecifically labeled estradiol, 2-hydroxyestradiol, and 4-hydroxyestradiol was also investigated, and the results are discussed in terms of the reactivity at different carbon atoms in ring A of the catechol estrogens. All the evidence points to conjugation of 4-hydroxyestradiol with glutathione or N-acetylcysteine at C-2 but not C-1 of this highly reactive catechol estrogen. Measuring the displacement of 3H as 3H2O from specific positions in the steroid ring provides a useful and sensitive method to assess the formation of adducts in cases where their isolation and characterization is particularly difficult.
- Research Organization:
- Queen's Univ., Kingston, Ontario (Canada)
- OSTI ID:
- 6325522
- Journal Information:
- Steroids; (United States), Vol. 51:3-4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ESTRADIOL
METABOLISM
ASCORBIC ACID
CYSTEINE
GLUTATHIONE
LIVER
MICROSOMES
RATS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
TYROSINASE
AMINO ACIDS
ANIMALS
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
DIGESTIVE SYSTEM
DRUGS
ENZYMES
ESTRANES
ESTROGENS
GLANDS
HORMONES
HYDROXY COMPOUNDS
HYDROXYLASES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MAMMALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANOIDS
ORGANS
OXIDOREDUCTASES
PEPTIDES
POLYPEPTIDES
PROTEINS
RADIOPROTECTIVE SUBSTANCES
RODENTS
STEROID HORMONES
STEROIDS
THIOLS
VERTEBRATES
VITAMINS
550501* - Metabolism- Tracer Techniques