title: Metabolic clearance rate of equilin sulfate and its conversion to plasma equilin, conjugated and unconjugated equilenin, 17 beta-dihydroequilin, and 17 beta-dihydroequilenin in normal postmenopausal women and men under steady state conditions.
abstract: The constant infusion of [3H]equilin sulfate ([3H]EqS) was used to estimate the MCR of equilin sulfate (EqS) and to measure the conversion of this estrogen to equilin (Eq), equilenin (Eqn), equilenin sulfate (EqnS), 17 beta-dihydroequilin (17 beta-Eq), 17 beta-dihydroequilin sulfate (17 beta-EqS), 17 beta-dihydroequilenin (17 beta-Eqn), and 17 beta-dihydroequilenin sulfate (17 beta-EqnS) in normal postmenopausal women and men. Infusion of [3H]EqS was started in five postmenopausal women and two men 30 min after a priming dose and continued at a constant rate of 12-15 microCi/h for 3 h. Blood samples were taken 15 min before the end of infusion, at the end of the infusion, and 15 min after the end of infusion. Unconjugated and sulfate-conjugated Eq, Eqn, 17 beta-Eq, and 17 beta-Eqn were isolated from plasma. The mean MCR of EqS was calculated to be 280 +/- 24 L/day or 170 +/- 18 L/day.m2. The mean conversion ratios for precursor EqS to product 17 beta-EqS, EqnS, 17 beta-EqnS, 17 beta-Eq, Eq, Eqn, and 17 beta-Eqn were 0.300, 0.190, 0.100, 0.020, 0.016, 0.008, and 0.004 respectively. In both the sulfate-conjugated and unconjugated forms, 17 beta-Eq was the most abundant metabolite formed. 17 beta-Eq estrogen is a potent uterotropic agent and has a much higher affinity for estrogen receptors than Eq. Its formation may be of importance in the overall biological activity of EqS present in conjugated equine estrogen preparations.
authors.affiliation: Department of Obstetrics and Gynecology, University of Toronto, Ontario, Canada.
authors.forename: B R
authors.initials: BR
authors.lastname: Bhavnani
authors.forename: A
authors.initials: A
authors.lastname: Cecutti
mesh_terms: D000368:Aged; D004855:Equilenin / Q000031:analogs & derivatives* / Q000378:metabolism*; D004857:Equilin / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D004966:Estrogens, Conjugated (USP) / Q000378:metabolism; D005260:Female; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D017698:Postmenopause; D012016:Reference Values
chemical_list: D004966:Estrogens, Conjugated (USP); D004857:Equilin; C037874:17-dihydroequilenin; C014482:dihydroequilin; C037875:equilin sulfate; D004855:Equilenin