title: Effect of catechol oestrogens on induced ovulation in the immature rat.
abstract: The 'positive feedback' effect of exogenous oestradiol-17 beta in advancing ovulation induced by pregnant mare serum gonadotrophin (PMSG) has been used in the present study as a model in which to test the possible oestrogenic or antioestrogenic effects of the catechol oestrogens, 2-hydroxyoestradiol (2-OHE2) and 4-OHE2. Sprague-Dawley rats of 26 days of age were injected with 20 i.u. 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 oestradiol was confirmed; 2-OHE2, in doses of up to 100 micrograms, influenced neither the time of ovulation nor the number of ova present but 4-OHE2 was equipotent with oestradiol in doses varying from 0.5 micrograms (the minimum effective dose for both steroids) to 10 micrograms. The possible antioestrogenic effect of 2-OHE2 was tested by giving a 100 micrograms dose either at the same time or 2 h before PMSG plus 2 micrograms oestradiol or 4-OHE2. The effects of oestradiol and 4-OHE2 were not altered by this treatment. These data show that, in this model of 'positive feedback', 2-OHE2 has neither an oestrogenic nor an antioestrogenic action but that 4-OHE2 has a potent oestrogenic action, thus raising the question of a physiological role for 4-OHE2 in the regulation of ovulation.
mesh_terms: D000818:Animals; D002396:Catechols / Q000494:pharmacology*; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D002393:Estrogens, Catechol; D005260:Female; D006064:Gonadotropins, Equine / Q000494:pharmacology; D010060:Ovulation / Q000187:drug effects*; D010062:Ovulation Induction; D051381:Rats; D012741:Sexual Maturation
chemical_list: D002396:Catechols; D004967:Estrogens; D002393:Estrogens, Catechol; D006064:Gonadotropins, Equine; D004958:Estradiol; C001390:2-hydroxyestradiol; C014036:4-hydroxyestradiol