INDUCTION OF PUBERTY IN IMMATURE FEMALE RAT - EFFECT OF ESTROGEN ON PITUITARY FSH AND STALK-MEDIAN-EMINENCE FSH-RELEASING FACTOR

Intact, 26-day-old female rats received daily injections (per 100 g body weight) of 0.05 μg estradiol benzoate (EB), 1 mg progesterone (P), 0.05 μg EB + 1 mg P, or 10 μg testosterone propionate (TP) in order to determine 1. if puberty could be advanced and+ 2. the related effects on hypophyseal follicle stimulating hormone (FSH) and stalk-median eminence (SME)-FSH-Relcasing Factor (FSHRF). EB alone caused vaginal opening to occur one week earlier on the average (day 32) than that observed in rats going through natural puberty (day 39). P, EB + P, and TP were ineffective in accelerating vaginal canalization. While SMF.-FSHRF activities and pituitary FSH concentrations of the rats receiving P, EB + P, and TP were equivalent to those of the oil-treated controls, the RF and its respective gonadotropin were markedly reduced in EB recipients and were similar to those observed in animals undergoing natural puberty. This indicated release of these two hormones to activate the ovarian-uterine-vaginal complex. Since the events occurring within the hypothalamic-hypophyseal unit of the EB-induced-puberty group and the natural-puberty group were concordant, the results imply that estrogen may be a significant factor in activating the FSHRF/FSH mechanism at puberal onset. These data supplement previous reports that estrogen alone can advance puberty via an activation of EHRF and LH. which is similar to that seen during normal puberty. © 1969 S. Karger AG, Basel.