title: Prolactin inhibits annexin 5 expression and apoptosis in the corpus luteum of pseudopregnant rats: involvement of local gonadotropin-releasing hormone.
abstract: We investigated a specific relationship between the expression of annexin 5 and prolactin in the corpus luteum of pseudopregnant rats, with particular interest in GnRH and apoptosis of luteal cells. The expression of ovarian annexin 5 mRNA was significantly decreased at mid-pseudopregnancy and recovered at the end, whereas it remained low on the corresponding day of pregnancy. The dopamine agonist CB-154, administered at mid-pseudopregnancy (d 5), increased ovarian annexin 5 mRNA, whereas prolactin, given daily for 3 d to cycling rats, decreased it. An immunocytochemical study also showed that annexin 5 increased in the corpus luteum on d 6 and 7 of pseudopregnancy after treatment with CB-154 on d 5. The distribution of annexin 5-positive cells was not uniform in the corpus luteum and matched that of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL)-positive cells. Because GnRH stimulates annexin 5 mRNA expression in the gonadotropes, involvement of the GnRH receptor was examined. Local administration of a GnRH antagonist, Cetrorelix, to hemilateral ovarian bursa of pseudopregnant rats simultaneously receiving CB-154 abrogated both the expression of annexin 5 and the TUNEL reaction. The present results clearly demonstrate that prolactin decreases annexin 5 mRNA in the luteal cells during pseudopregnancy. Prolactin is suggested to suppress the local action of GnRH, which stimulates annexin 5 synthesis and apoptosis of functional luteal cells during pseudopregnancy.
authors.affiliation: Veterinary Physiology, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori 034-8628, Japan. mitsumor@vmas.kitasato-u.ac.jp
authors.forename: Mitsumori
authors.initials: M
authors.lastname: Kawaminami
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Shibata
authors.forename: Akiko
authors.initials: A
authors.lastname: Yaji
authors.forename: Shiro
authors.initials: S
authors.lastname: Kurusu
authors.forename: Inoru
authors.initials: I
authors.lastname: Hashimoto
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000032:analysis / Q000235:genetics*; D017209:Apoptosis / Q000187:drug effects; D015152:Blotting, Northern; D001971:Bromocriptine / Q000494:pharmacology; D003338:Corpus Luteum / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects; D018491:Dopamine Agonists / Q000494:pharmacology; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D011388:Prolactin / Q000494:pharmacology / Q000502:physiology*; D011555:Pseudopregnancy; D051381:Rats; D017208:Rats, Wistar
chemical_list: D017304:Annexin A5; D018491:Dopamine Agonists; D007987:Gonadotropin-Releasing Hormone; D001971:Bromocriptine; D011388:Prolactin; C062876:cetrorelix