Abstract
The role of the conjugate in the biosynthesis of 2-methoxyestrogen in the living animal has been explored by the double-isotope technique. The isotope ratios of the isomeric catechol estrogen monomethyl ethers excreted in urine after simultaneous administration of estrone-4-14C and estrone-6, 7-3H sulfate or estradiol-6, 7-3H 3-glucuronide were determined. Comparison of the 3H/14C value with that of the administered steroid implies that the sulfate conjugation may possibly participate in the predominant formation of 2-methoxyestrogen, while the conjugation with glucuronic acid may not. The dimethyl ether of catechol estrogen was metabolized with random O-demethylation yielding two isomeric monomethyl ethers both in the rat and man. Therefore it appears that the selective O-demethylation may not be involved in the preferential formation of 2-methoxyestrogen.
