Sulphation and glucuronidation of ethinyloestradiol in human liver in vitro.
The sulphotransferase and the glucuronyltransferase activities were measured with [3H]ethinyloestradiol in vitro using subcellular fractions from human liver. A rapid and sensitive assay based on a single extraction in ether of the unmetabolized EE2 is described. The mean (+/- SD) of the sulphotransferase and glucuronyltransferase activities from 8 livers was 68.2 +/- 16.5 and +/- 190.4 +/- 82.3 pmol/min/mg, respectively. The kinetic parameters of both enzymes were measured in 4 livers by varying the concentrations of EE2 or the endogenous substrate. At varying concentrations of EE2 the average (+/- SD) of Vmax was 66.5 +/- 15.8 pmol/min/mg (sulphotransferase) and 404 +/- 317 pmol/min/mg (glucuronyltransferase). The mean (+/- SD) of Km was 0.0072 +/- 0.0019 mM (sulphotransferase) and 0.20 +/- 0.12 mM (glucuronyltransferase).
D000293:Adolescent; D001711:Biotransformation; D003600:Cytosol / Q000378:metabolism; D004997:Ethinyl Estradiol / Q000378:metabolism*; D005260:Female; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D008875:Middle Aged; D013466:Sulfurtransferases / Q000378:metabolism*
D004997:Ethinyl Estradiol; D014453:Glucuronosyltransferase; D013466:Sulfurtransferases