Journal of Clinical Endocrinology & Metabolism, Vol 77, 1269-1274, Copyright © 1993 by Endocrine Society

ARTICLES

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

BR Bhavnani and A Cecutti
Department of Obstetrics and Gynecology, University of Toronto, Ontario, Canada.

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.

This article has been cited by other articles:

				B. R. Bhavnani, A. Cecutti, and A. Gerulath Pharmacokinetics of 17{beta}-Dihydroequilin Sulfate in Normal Postmenopausal Women Under Steady State Conditions Reproductive Sciences, March 1, 2002; 9(2): 102 - 110. [Abstract] [PDF]

				B. R. Bhavnani, J. A. Nisker, J. Martin, F. Aletebi, L. Watson, and J. K. Milne Comparison of Pharmacokinetics of a Conjugated Equine Estrogen Preparation (Premarin) and a Synthetic Mixture of Estrogens (C.E.S.) in Postmenopausal Women Reproductive Sciences, May 1, 2000; 7(3): 175 - 183. [Abstract] [PDF]

				B. R. Bhavnani, A. Cecutti, and M. S. Dey Biologic Effects of Delta-8-Estrone Sulfate in Postmenopausal Women Reproductive Sciences, May 1, 1998; 5(3): 156 - 160. [Abstract] [PDF]