Charcoal-catalyzed transfer of tritium into 3H2O from regiospecifically-labeled 2-hydroxyestradiol in the presence of thiols.
Charcoal was found to catalyze the release of 3H2O from [1-3H]2-hydroxyestradiol-17 beta ([1-3H]2-OHE2) or [4-3H]2-hydroxyestradiol-17 beta ([4-3H]2-OHE2) and this effect was shown to occur in the presence of glutathione or other thiols and to depend on the concentration of free steroid. The radiometric assay for measuring the formation of 3H2O was not affected significantly by subsequent treatment of the incubation mixture with charcoal if the ratio of steroid to tissue (rat brain or liver microsomes) was low and only initial rates of 3H release were measured. 2-Hydroxyestradiol did not show the charcoal effect in the presence of tyrosinase, either when it was generated from its parent estrogen or added to the enzyme. The formation of 3H2O from [4-3H]2-OHE2 in the presence of glutathione was inhibited by ascorbic acid but the addition of dextran or albumin did not protect the catechol estrogen from the charcoal-catalyzed loss of tritium. The reaction with glutathione and charcoal occurred even at 4 degrees C but other adsorbants such as alumina, silica or hydroxylapatite were without effect.
D002384:Catalysis; D002606:Charcoal; D004958:Estradiol / Q000031:analogs & derivatives*; D005978:Glutathione; D013438:Sulfhydryl Compounds; D014316:Tritium
D013438:Sulfhydryl Compounds; D014316:Tritium; D002606:Charcoal; D004958:Estradiol; C001390:2-hydroxyestradiol; D005978:Glutathione