The ovary-mediated FSH attenuation of the LH surge in the rat involves a decreased gonadotroph progesterone receptor (PR) action but not PR expression.
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.
Gordon
Ana
A
Departments of Cell Biology, Physiology and Immunology and Comparative Pathology, University of Córdoba, 14004 Córdoba, Spain IVI Madrid, Madrid, Spain.
Garrido-Gracia
José C
JC
Aguilar
Rafaela
R
Bellido
Carmina
C
Velasco
Juan A García
JA
Millan
Yolanda
Y
Tena-Sempere
Manuel
M
Martín de Las Mulas
Juana
J
Sánchez-Criado
José E
JE
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
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