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Effect of catechol oestrogens on induced ovulation in the immature rat


, : Effect of catechol oestrogens on induced ovulation in the immature rat. Journal of Endocrinology 86(2): 263-268

The positive feedback effect of exogenous estradiol-17.beta. in advancing ovulation induced by pregnant mare serum gonadotropin (PMSG) was used in the study as a model to test the possible estrogenic or antiestrogenic effects of the catechol estrogens, 2-hydroxyestradiol (2-OHE2) and 4-OHE2. Sprague-Dawley rats of 26 days of age were injected with 20 IU PMSG together with either vehicle alone or test steroids. The animals were killed 72 h later and the Fallopian tubes were examined for the presence of ova. Advancement of induced ovulation by treatment with estradiol was confirmed; 2-OHE2, in doses of up to 100 .mu.g, influenced neither the time of ovulation nor the number of ova present, but 4-OHE2 was equipotent with estradiol in doses varying from 0.5 .mu.g (the minimum effective dose for both steroids) to 10 .mu.g. The possible antiestrogenic effect of 2-OHE2 was tested by giving a 100 .mu.g dose either at the same time or 2 h before PMSG plus 2 .mu.g estradiol or 4-OHE2. The effects of estradiol and 4-OHE2 were not altered by this treatment. In this model of positive feedback, 2-OHE2 apparently has neither an estrogenic nor an antiestrogenic action but 4-OHE2 has a potent estrogenic action, thus raising the question of a physiological role for 4-OHE2 in the regulation of ovulation.

US$19.90

PMID: 6253586

DOI: 10.1677/joe.0.0860263


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