The Inhibitory Effects of ACTH and Adrenalectomy on Reproductive Maturation in Female Rats

Publisher Website
Google Scholar
Abstract
The delay of sexual maturation resulting from ACTH treatment and adrenalectomy in female rats was studied. ACTH (4 IU/100 g body wt) was administered daily to intact and adrenalectomized [ADX] female Sprague-Dawley rats beginning on the day of weaning (day 21) and continuing until day 40. Animals were decapitated at 1600 h on days 25, 30, 35, 40 and on the day of vaginal opening; blood samples collected were assayed for progesterone, corticosterone, LH [luteinizing hormone] and prolactin. Animals were also sacrificed on 1st estrus and the Fallopian tubes were examined for the number of ova present. Either chronic ACTH treatment of intact animals or ADX delayed vaginal opening by 4 days. The inhibitory action of ACTH on vaginal opening possibly is mediated by the adrenal glands, since ACTH-injected ADX rats failed to show a delay in vaginal patency. These animals exhibited a significant reduction in the number of ova present on 1st estrus as well as significantly lower body weights at vaginal opening. Plasma progesterone and corticosterone levels were elevated in ACTH-treated intact rats that exhibited delayed vaginal opening. Only plasma corticosterone was elevated in vehicle-injected rats that did not show retarded sexual maturation. Although chronically elevated levels of plasma progesterone in ACTH-treated rats may inhibit sexual maturation by interfering with LH secretion, attempts to demonstrate a suppression of plasma LH concentrations in these animals were unsuccessful.