Sexually dimorphic expression of gonadotropin subunits in the pituitary of protogynous honeycomb grouper (Epinephelus merra): Evidence that follicle-stimulating hormone (FSH) induces gonadal sex change

Yasuhisa Kobayashi, Mohammad Ashraful Alam, Ryo Horiguchi, Akio Shimizu, Masaru Nakamura

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

Recent studies have suggested that the hypothalamic-pituitary-gonadal axis is involved in gonadal sex change in sex-changing teleosts. However, its underlying mechanism remains largely unknown. In this study, we focused on the distinct roles of two gonadotropins (GTHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), in the protogynous hermaphrodite teleost, honeycomb grouper (Epinephelus merra). First, we investigated the expression pattern of mRNAs for GTH subunits (cga, fshb, and lhb) in the pituitaries from fish at the different sexual phases. Real-time RT-PCR analyses showed that fhsb mRNA levels in the female pituitary were low. However, fshb transcripts increased dramatically in association with testis development. In contrast, levels of cga and lhb mRNAs did not significantly vary during sex change. In addition, immunohistochemical observations of Fshb- and Lhb-producing cells in the pituitary, through the use of specific antibodies for detections of teleost GTH subunits, were consistent with sexually dimorphic expression of Fshb. In order to identify the role of GTH in gonad of honeycomb grouper, we treated females with bovine FSH (50 or 500 ng/fish) or LH (500 ng/fish) in vivo. After 3 wk, FSH treatments induced female-to-male sex change and up-regulated endogenous androgen levels and fshb transcripts, whereas LH treatment had no effect on sex change. These results suggest that FSH may trigger the female-to-male sex change in honeycomb grouper.

Original languageEnglish
Pages (from-to)1030-1036
Number of pages7
JournalBiology of reproduction
Volume82
Issue number6
DOIs
Publication statusPublished - Jun 1 2010

Keywords

  • Androgen
  • Estrogen
  • Follicle-stimulating hormone
  • Gonadotropin
  • Grouper
  • Luteinizing hormone
  • Ovary
  • Pituitary hormones
  • Sex change
  • Teleost

ASJC Scopus subject areas

  • Reproductive Medicine
  • Cell Biology

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