The effect of aminoglutethimide on steroid secretion, ovulation, and luteinizing hormone release in the hen

An injection of 200 mg aminoglutethimide (AG)/kg body weight (BW) given 9 hr before spontaneous midcycle ovulation reliably blocked ovarian steroidogenesis and ovulation. Reduction of the dose to 100 mg AG/kg BW or injection of either dose 7 hr before ovulation partially blocked steroidogenesis and failed to reliably inhibit ovulation. Both doses of AG given either 7 or 9 hr before ovulation completely inhibited estradiol-17 beta secretion. Plasma concentrations of progesterone were partially reduced by 100 mg AG/kg BW and were completely suppressed by the 200 mg/kg BW dose of AG. Plasma testosterone levels were depressed only by 200 mg AG/kg BW. Plasma corticosterone levels were elevated following all injections of AG. In the absence of ovarian steroidogenesis, the plasma concentration of luteinizing hormone either remained stable or decreased slightly. Estradiol-17 beta synthesis or release is not required for ovulation, because, in some cases, ovulation occurred in the absence of this hormone. Derangement of the ovarian hierarchy usually occurred when AG was given 7 hr but not 9 hr before ovulation.