Administration of 6,7-3H-estradiol- 17β to mature ovariectomized rats results in the labeling of 2 pools of estradiol-17β in the uterus. Half-lives of the 2 pools are 0.7 and 5 hr. Intraluminal (IL) uterine application of 10 μg of estradiol-17α 6 hr after administration of 3Hestradiol- 17β is capable of enhancing the rate of displacement of the previously bound active estrogen from the uterus. By the 12th hr the uterine levels are 30-50% less than in saline treated controls. The reduced estradiol-17β content is reflected in the relative labeling of uterine chromatin prepared from the 2 groups. When assayedassayed for its capacity to serve as a template for DNA-dependent RNA polymerase, it was found that treatment with estradiol-17α prevented the additional increase in template capacity of uterine chromatin normally observed to occur between the 6th and 12th hr after treatment with estradiol-17β. These results suggest that estradiol- 17α and perhaps other estrogenic compounds with subdued biological activity may well able to inhibit certain estrogen induced uterine responses which are in progress at the time treatment. (Endocrinology83: 585, 1968)
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Barker et al. (1968) studied this question.