title: Gonadotropin releasing hormone agonists stimulate oocyte meiosis and ovulation in hypophysectomized rats.
abstract: The acute effects in vivo of gonadotropin releasing hormone (GnRH) and a potent agonistic analogue (GnRHa) were tested in PMSG-treated immature female rats, hypophysectomized on the morning of proestrus. The rats were injected once with either LH, GnRH, or GnRHa 3-4 h after surgery, and the effects on oocyte meiosis, ovulation, and plasma progesterone were investigated. LH (25 microgram) and GnRHa (12.0 and 1.2 microgram) caused a high rate of meiosis, while GnRH (100 microgram) or GnRHa (0.12 microgram) caused a partial response. LH and GnRHa produced ovulation in all of the treated rats and caused a prolonged increase in plasma progesterone levels. It is concluded that GnRH agonists exert acute stimulatory effects in the ovarian follicle, independent of pituitary factors.
mesh_terms: D000818:Animals; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006064:Gonadotropins, Equine / Q000494:pharmacology; D006728:Hormones / Q000494:pharmacology*; D007016:Hypophysectomy; D008540:Meiosis / Q000187:drug effects*; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D010060:Ovulation / Q000187:drug effects*; D010063:Ovum / Q000502:physiology*; D051381:Rats
chemical_list: D006064:Gonadotropins, Equine; D006728:Hormones; D007987:Gonadotropin-Releasing Hormone; C010661:surfagon