Direction of Estradiol Metabolism as a Control of its Hormonal Action—Uterotrophic Activity of Estradiol Metabolites

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Abstract
The uterotrophic activities of the catechol metabolites of estradiol 2-hydroxyestrone, 2-methoxyestrone and 2-hydroxyestradiol were measured under conditions of continuous administration [to rats] from s.c. implanted paraffin pellets. The activity of these estrogens was compared to that of estradiol-17.beta. and its other principal metabolites estrone, estriol and 15.alpha.-hydroxyestriol (estetrol). The major catechol estrogens, 2-hydroxyestrone and 2-methoxyestrone, and the pregnancy metabolite, 15.alpha.-hydroxyestriol, exhibited no uterotrophic activity. The minor catecholestrogen 2-hydroxyestradiol, showed some activity whose character was different from that exhibited by implants of estradiol, estrone and estriol all of which were equipotent uterotrophic agents. Implants of 2-hydroxyestrone in the presence of estradiol or estriol pellets did not diminish the response to the latter, indicating that the 2-hydroxyestrone is not antiestrogenic under these conditions. The direction of estradiol metabolism can have a profound influence on the expression of peripheral hormonal activity with hydroxylation at G-2 terminating and hydroxylation at C-16 extending it.

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