title: The ovary-mediated FSH attenuation of the LH surge in the rat involves a decreased gonadotroph progesterone receptor (PR) action but not PR expression.
abstract: Hyperstimulation of ovarian function with human FSH (hFSH) attenuates the preovulatory surge of LH. These experiments aimed at investigating the mechanism of ovarian-mediated FSH suppression of the progesterone (P(4)) receptor (PR)-dependent LH surge in the rat. Four-day cycling rats were injected with hFSH, oestradiol benzoate (EB) or vehicle during the dioestrous phase. On pro-oestrus, their pituitaries were studied for PR mRNA and protein expression. Additionally, pro-oestrous pituitaries were incubated in the presence of oestradiol-17beta (E(2)), and primed with P(4) and LH-releasing hormone (LHRH), with or without the antiprogestin RU486. After 1 h of incubation, pituitaries were either challenged or not challenged with LHRH. Measured basal and LHRH-stimulated LH secretions and LHRH self-priming were compared with those exhibited by incubated pituitaries on day 4 from ovariectomized (OVX) rats in metoestrus (day 2) injected with hFSH and/or EB on days 2 and 3. The results showed that: i) hFSH lowered the spontaneous LH surge without affecting basal LH and E(2) levels, gonadotroph PR-A/PR-B mRNA ratio or immunohistochemical protein expression; ii) incubated pro-oestrous pituitaries from hFSH-treated rats did not respond to P(4) or LHRH, and lacked E(2)-augmenting and LHRH self-priming effects and iii) OVX reversed the inhibitory effects of hFSH on LH secretion. It is concluded that under the influence of hFSH, the ovaries produce a non-steroidal factor which suppresses all PR-dependent events of the LH surge elicited by E(2). The action of such a factor seemed to be due to a blockade of gonadotroph PR action rather than to an inhibition of PR expression.
authors.affiliation: Departments of Cell Biology, Physiology and Immunology and Comparative Pathology, University of Córdoba, 14004 Córdoba, Spain IVI Madrid, Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Gordon
authors.forename: José C
authors.initials: JC
authors.lastname: Garrido-Gracia
authors.forename: Rafaela
authors.initials: R
authors.lastname: Aguilar
authors.forename: Carmina
authors.initials: C
authors.lastname: Bellido
authors.forename: Juan A García
authors.initials: JA
authors.lastname: Velasco
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Millan
authors.forename: Manuel
authors.initials: M
authors.lastname: Tena-Sempere
authors.forename: Juana
authors.initials: J
authors.lastname: Martín de Las Mulas
authors.forename: José E
authors.initials: JE
authors.lastname: Sánchez-Criado
mesh_terms: D000818:Animals; D004031:Diestrus / Q000187:drug effects / Q000502:physiology; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004971:Estrus / Q000187:drug effects / Q000502:physiology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D043373:Follicle Stimulating Hormone, Human / Q000494:pharmacology*; D005498:Follicular Phase / Q000187:drug effects / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D052681:Gonadotrophs / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism*; D008186:Luteolytic Agents / Q000494:pharmacology; D015735:Mifepristone / Q000494:pharmacology; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology; D011359:Proestrus / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011980:Receptors, Progesterone / Q000235:genetics / Q000378:metabolism*; D014599:Uterus / Q000187:drug effects / Q000502:physiology; D014621:Vagina / Q000166:cytology / Q000187:drug effects / Q000502:physiology
chemical_list: D043373:Follicle Stimulating Hormone, Human; D008186:Luteolytic Agents; D012333:RNA, Messenger; D011980:Receptors, Progesterone; C101118:progesterone receptor A; C097314:progesterone receptor B; C074283:estradiol 3-benzoate; D015735:Mifepristone; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone