Changes in pituitary secretion during the early postnatal period and anovulatory syndrome induced by neonatal oestrogen or androgen in rats

The following experiments were performed: (i) concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin in plasma were measured at 2, 5, 8, 10 and 15 days in female Wistar rats treated on the first day of life with 100 micrograms oestradiol benzoate or vehicle; (ii) females injected on day 1 with 100 micrograms of oestradiol benzoate or 1 mg of testosterone propionate and from day 1 to day 10 or 15 with FSH and LH were killed on day 90; (iii) females injected from day 1 to day 10 or 15 with prolactin or vehicle were killed on day 90; (iv) females injected on day 1 with oestradiol benzoate and from day 1 to day 15 with a luteinizing-hormone-releasing hormone (LHRH) agonist were killed on day 90; (v) groups of females injected on days 1, 4, 7, 10, 13 and 16 with an LHRH antagonist were killed on day 90. Onset of puberty, vaginal cycles, organ weights and hormonal plasma concentrations were measured. Females treated on the first day of life with 100 micrograms oestradiol showed inhibition of gonadotrophin secretion and stimulation of prolactin secretion during the neonatal period. Females injected on the first day of life with oestradiol benzoate or testosterone propionate showed, in adulthood, anovulation, ovarian atrophy, reduced FSH plasma concentrations, increased prolactin plasma concentrations and reduced pituitary prolactin content.(ABSTRACT TRUNCATED AT 250 WORDS)

Are eosinophil leucocytes involved in the oestrogenic response of the postnatal rat epididymis?

The effects of oestrogens and androgens, alone or in combination, on several epididymal parameters have been studied in 15-day-old rats after neonatal treatment. Oestrogens induced several responses, such as increased growth of the fibromuscular stroma and eosinophil leucocyte accumulation, whereas the proliferative activity of the epithelium was decreased significantly. Otherwise, the density of intra-epithelial leucocytes was not modified. Different oestrogen-induced responses, such as the increase in volume of the fibromuscular stroma and eosinophil leucocyte accumulation were inhibited by treatment with testosterone, whereas dihydrotestosterone had no appreciable effect. This study raises the possibility that eosinophils are mediators of some of the oestrogenic responses in the early postnatal rat epididymis.

A possible dual mechanism of the anovulatory action of antiprogesterone RU486 in the rat

The purpose of these experiments was to investigate the mechanism of the anovulatory action of antiprogesterone RU486 (RU486) in rats by studying its effects on follicular growth, secretion of gonadotropins and ovarian steroids, and ovulation. Rats with 4-day estrous cycles received injections (s.c.) of either 0.2 ml oil or 0.1, 1, or 5 mg of RU486 at 0800 and 1600 h on metestrus, diestrus, and proestrus. At the same times, they were bled by jugular venipuncture to determine serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), 17 beta-estradiol (E), and progesterone (P). On the morning of the day after proestrus, ovulation and histological features of the ovary were recorded. Rats from each group were killed on each day of ovarian cycle to assess follicular development. Rats treated similarly were decapitated at the time of the ovulatory LH surge and blood was collected to measure LH. The serum levels of LH increased and those of FSH decreased during diestrus in rats treated with RU486. Neither E nor P levels differed among the groups. Treatment with RU486 caused both a blockade of the ovulation and an increase in ovarian weight in a dose-dependent manner. At the time of the autopsy (the expected day of ovulation), rats treated with 1 mg RU486 had ovaries presenting both normal and post-ovulatory follicles and unruptured luteinized follicles. Rats treated with 5 mg RU486 presented post-ovulatory follicles without signs of luteinization. The number of follicles undergoing atresia increased in rats treated with RU486. Rats treated with 5 mg RU486 exhibited a significant decrease in ovulatory LH release. The mechanism by which RU486 produces the ovulatory impairment in rats seems to be dual: first, by inducing inadequate follicular development at the time of the LH surge and second, by reducing the amount of ovulatory LH released. The physiological events-decreased basal FSH secretion and follicular atresia-that result from use of RU486 cannot be elucidated from these experiments and should be investigated further.

Prepuberal reproductive defects in neonatal estrogenized male rats

Intact Wistar male rats injected on Day 1 with 500 micrograms of estradiol benzoate or olive oil were decapitated on Days 15 and 22 or maintained until adulthood to analyze the balanopreputial separation. Other oil or estradiol-treated rats were orchidectomized on Day 15 and decapitated on Day 22. The neonatal estrogenization produced the following reproductive changes prior to puberty: testis, adrenal, and ventral prostate atrophy; increase in the weights of seminal vesicles and epididymis; decrease in testosterone plasma levels; delayed balanopreputial separation; abolition of luteinizing hormone response to orchidectomy; transient increase in prolactin plasma levels; and blockade in seminal and prostate response to orchidectomy.