Pre-ovulatory augmentation of metastin mRNA expression in follicles of rats

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 561-585-Ovarian & Uterine Function II
Basic/Clinical
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-570
Titaree Laoharatchatathanin*, Ryota Terashima, Tomohiro Yonezawa, Shiro Kurusu and Mitsumori Kawaminami
Kitasato Univ, Aomori, Japan
Metastin (also called kisspeptin) is the product of Kiss-1 metastasis-suppressor gene and the intrinsic ligand of GPR54. It stimulates the release of gonadotoropin releasing hormone (GnRH) in the hypothalamus. Although metastin is known to be synthesized also in the ovary, physiological significance of ovarian metastin is so far unknown. We investigated, in the present study, 1) precise changes in the expression of ovarian metastin mRNA during the estrous cycle of rats, 2) how its expression is controlled, 3) which ovarian compartment synthesizes metastin and 4) whether metastin is involved in ovarian GnRH synthesis or not. Ovarian GPR54, metastin and GnRH mRNAs were measured by real-time RT-PCR. Whole ovary RNA was used. GPR54 mRNA started to increase from diestrous 2 and showed a peak at 14:00 h of proestrus. Metastin mRNA expression showed a steep single peak at 20:00 h of proestrus. There were two peaks in the variation of GnRH mRNA expression rate, one was at 20:00 h of diestrous 2 and another was synchronized with that of metastin at 20:00 h of proestrus. The increase of metastin mRNA at 20:00 h of proestrus was suppressed by GnRH antagonist or pentobarbital given at 12:00 h of proestrus. Metastin mRNA expression was augmented 3 h after hCG administration (D2 14:00 h, 10IU i.v.). Hence, the observed peak of metastin mRNA expression at 20:00 h of proestrus is suggested to be induced by LH surge. Metastin was demonstrated by immunohistochemistry to distribute to almost all compartments of the ovary. However, when follicle, corpus luteum and interstitial tissues were separately collected by laser micro dissection, only follicles contained significant amount of metastin mRNA. Furthermore, the follicular expression rate of metastin mRNA at 20:00 h of proestrus was more than that of hypothalamus. Three h after hCG iv injection follicular metastin mRNA was significantly increased. Metastin 45-54, kiss-10, given into ovarian bursa significantly stimulated GnRH mRNA expression in the ovary. Present data clearly showed that metastin synthesis is precisely regulated by LH surge and suggest at least that GnRH mRNA expression is augmented by metastin in the ovary before the ovulation.

Nothing to Disclose: TL, RT, TY, SK, MK

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