Hypophysiotropic role of RFamide-related peptide-3 in the inhibition of LH secretion in female rats

Masahiro Murakami, Toshiya Matsuzaki, Takeshi Iwasa, Toshiyuki Yasui, Minoru Irahara, Tomohiro Osugi, Kazuyoshi Tsutsui

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    Abstract

    Gonadotropin-inhibitory hormone (GnIH), a newly discovered hypothalamic RFamide peptide, inhibits reproductive activity by decreasing gonadotropin synthesis and release in birds. The gene of the mammalian RFamide-related peptides (RFRP) is orthologous to the GnIH gene. This Rfrp gene gives rise to the two biologically active peptides RFRP-1 (NPSF) and RFRP-3 (NPVF), and i.c.v. injections of RFRP-3 suppress LH secretion in several mammalian species. In this study, we show whether RFRP-3 affects LH secretion at the pituitary level and/or via the release of GnRH at the hypothalamus in mammals. To investigate the suppressive effects of RFRP-3 on the mean level ofLH secretion and the frequency of pulsatile LH secretion in vivo, ovariectomized (OVX) mature rats were administered RFRP-3 using either i.c.v. or i.v. injections. Furthermore, the effect of RFRP-3 on LH secretion was also investigated using cultured female rat pituitary cells. With i.v. administrations, RFRP-3 significantly reduced plasma LH concentrations when compared with the physiological saline group. However, after i.c.v. RFRP-3 injections, neither the mean level of LH concentrations nor the frequency of the pulsatile LH secretion was affected. When using cultured pituitary cells, in the absence of GnRH, the suppressive effect of RFRP-3 on LH secretion was not clear, but when GnRH was present, RFRP-3 significantly suppressed LH secretion. These results suggest that RFRP-3 does not affect LH secretion via the release of GnRH, and that RFRP-3 directly acts upon the pituitary to suppress GnRH-stimulated LH secretion in female rats.

    Original languageEnglish
    Pages (from-to)105-112
    Number of pages8
    JournalJournal of Endocrinology
    Volume199
    Issue number1
    DOIs
    Publication statusPublished - 2008 Oct

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    ASJC Scopus subject areas

    • Endocrinology
    • Endocrinology, Diabetes and Metabolism

    Cite this

    Murakami, M., Matsuzaki, T., Iwasa, T., Yasui, T., Irahara, M., Osugi, T., & Tsutsui, K. (2008). Hypophysiotropic role of RFamide-related peptide-3 in the inhibition of LH secretion in female rats. Journal of Endocrinology, 199(1), 105-112. https://doi.org/10.1677/JOE-08-0197