Effect of Estrogen and Anti-estrogen on Reproductive Function in Neonatally Androgenized Female Rats

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Abstract
Estradiol benzoate (EB) and ethamoxytriphetol (MER-25)2 were administered during puberty in an attempt to influence time of occurrence of the anovulatory syndrome and degree of receptivity in neonatally androgenized rats. When 5 days old, Sprague-Dawley female rats were injected with either oil or 3, 5, 10 or 50 tig testosterone propionate (TP) and, when 26 days old, with either 20 μg EB for 5 or 10 successive days or 5.0 mg MER-25 or oil for 10 days. All subjects were ovariectomized between 81 and 90 days of age and after 1 week received the first of 3 weekly receptivity tests with vigorous males. Heat was induced by injecting 10 μg EB followed 44 hr later by 0.5 mg progesterone. For the most part, the effect of EB and MER-25 on age of vaginal opening was independent of neonatal androgen treatment. EB advanced by approximately 5 days and MER-25 delayed by 6 days onset time of vaginal canalization. Age of onset of persistent vaginal estrus (PVE) was inversely related to neonatal TP dosage. EB increased by a constant amount the percentage of subjects exhibiting PVE at each age. When measured from age of vaginal opening, however, the percentage of subjects exhibiting PVE was the same in the oil, EB, and MER-25 groups. Degree of receptivity was inversely related to amount of neonatally injected TP and not significantly affected by EB administered during puberty. Androgenized subjects injected with MER-25 exhibited more receptivity than those receiving oil. The results were interpreted as indicating that, while EB advanced and MER- 25 delayed puberty, neither directly influenced the duration of the period of normal vaginal and ovarian cyclicity antecedent to the occurrence of the anovulatory syndrome. Receptivity in androgenized subjects, however, appeared to be influenced by MER-25 present during puberty, suggesting dissociation between physiological and behavioral effects induced by exogenous hormones.

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