Expressions of GnRH and GnRH receptor mRNA in female rats with danazol-induced precocious puberty

Objective To ob se rve the effects of danazol on hypothalamus-pituitary-gonad axises and expressi ons of hypothalamic GnRH and pituitary GnRH receptor mRNA in female rats. Methods Female rats at 5 days of age were given a sin gle subcutaneous injection of 300 μg danazol to induce true precocious puberty. Animals were divided into 3 groups: normal control, model group and vehicle gro up. The day of vaginal opening from 25 days of age was monitored, and the establ ishment of first estrus cycle from the day of vaginal opening was investigated b y examination of vaginal smears. The weights of body, pituitary, adrenal, uterus and ovary were measured to identify the developmental status of main organs. Th e expressions of hypothalamic GnRH and pituitary GnRH receptor mRNA were assayed by semi-quantitative RT-PCR. Results Female rats treated with danazol significantly (P0.01, respective ly) advanced the day of vaginal opening 〔(34.0±1.0)days vs (26.0±2.2)days〕 and first estrus 〔(41.3±2.4)days vs (32 .4±0.8)days〕. The ovary and uterus organ coefficients were higher in model gro up than those in normal control. GnRH and GnRH receptor mRNA were significantly increased in the female precocious puberty rats induced by danazol. Conclusion Danazol advances the onset of hypothalamus-pitu itary-ovary axis function, this precocious rat could represent a model for stud ying the mechanism of puberty.