Luteinizing-Hormone-Mediated Precocious Puberty Induced in Female Rats by a Prepuberal Pituitary Graft

Abstract

The present study analyzes the mechanism of precocious puberty induced in female rats after a ‘young’ pituitary graft (obtained from 21-day-old animals). For this purpose, the following experiments have been performed: (1) female rats were grafted or sham-operated on day 21 with a littermate’s pituitary the follicle-stimulating hormone (FSH), luteinizing hormone (LH) and estradiol plasma levels as well as the ovarian, uterine and adrenal weights were determined at different times after the graft; (2) female rats grafted or sham-operated on day 21 were treated with 0.2 ml of LH antiserum (LHAS) or the same volume of a normal horse serum (NHS); (3) female rats were injected on day 1 of life with 0.1 mg of estradiol benzoate or olive oil. Groups of these animals were decapitated daily between days 6 and 21 in order to measure gonadotropins and prolactin (PRL) pituitary content. Since on day 21 estrogenized females showed decreased gonadotropin content and normal PRL content, females in experiment 4 were grafted on day 21 with pituitaries obtained from control or neonatally estrogenized female rats. The results obtained showed that FSH, LH and estradiol plasma levels as well as ovarian and uterine weights increased after pituitary grafts. LHAS blocked the precocious puberty induced by the pituitary graft, and pituitaries obtained from neonatally estrogenized female rats were unable to modify the occurrence of puberty when grafted. In conclusion, this work evidences that precocious puberty induced by ‘young’ pituitary grafts was mediated by the increase in LH secretion from the graft.

Mechanisms for altered reproductive function in female rats following neonatal administration of raloxifene

“…Female rats injected neonatally with estrogen developed a permanent anovulatory syndrome in adulthood (5, 6, 9, 18, 24), which is preceded by a strong reduction in pituitary content and secretion of gonadotropins immediately after neonatal injection of estrogen (9,25). Similarly, the results now reported indicate that raloxifene-treated rats exhibited a decrease in pituitary content and plasma concentrations of gonadotropins after treatment that was followed in adulthood by a permanent anovulatory syndrome.…”

Evaluation of the true precocious puberty rats induced by neonatal administration of Danazol: Therapeutic effects of nourishing "Yin"- removing "Fire" Chinese herb mixture

“…Nevertheless, our results, the GnRH mRNA expression showed a higher level in the precocious puberty model rats than in the same age normal rats, the blood estrogen concentration in the model group is twofold higher than that in normal one, along with the day of vaginal opening and the onset of regular estrous cycle advanced significantly in the model rats, give more evidence to sustain the hypothesis that the model induced by neonatal treatment with Danazol is a true precocious puberty model, and might be served to study the onset mechanism of puberty. Besides, though experimental models of precocious puberty have been induced in female rats from 15 to 30 days of age [11,13] or during neonate, by testosterone, estradiol, melatonin and so on, this model appears the subsequent normal ovulatory cycles during adulthood [3]. …”