'Free' inhibin α subunit is expressed by bovine ovarian theca cells and its knockdown suppresses androgen production

Sci Rep. 2019 Dec 24;9(1):19793. doi: 10.1038/s41598-019-55829-w.

Abstract

Inhibins are ovarian dimeric glycoprotein hormones that suppress pituitary FSH production. They are synthesised by follicular granulosa cells as α plus βA/βB subunits (encoded by INHA, INHBA, INHBB, respectively). Inhibin concentrations are high in follicular fluid (FF) which is also abundant in 'free' α subunit, presumed to be of granulosal origin, but its role(s) remains obscure. Here, we report the unexpected finding that bovine theca cells show abundant INHA expression and 'free' inhibin α production. Thus, theca cells may contribute significantly to the inhibin α content of FF and peripheral blood. In vitro, knockdown of thecal INHA inhibited INSL3 and CYP17A1 expression and androgen production while INSL3 knockdown reduced INHA and inhibin α secretion. These findings suggest a positive role of thecal inhibin α on androgen production. However, exogenous inhibin α did not raise androgen production. We hypothesised that inhibin α may modulate the opposing effects of BMP and inhibin on androgen production. However, this was not supported experimentally. Furthermore, neither circulating nor intrafollicular androgen concentrations differed between control and inhibin α-immunized heifers, casting further doubt on thecal inhibin α subunit having a significant role in modulating androgen production. Role(s), if any, played by thecal inhibin α remain elusive.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Androgens / metabolism*
  • Animals
  • Cattle
  • Endocrine System
  • Female
  • Follicular Fluid / metabolism*
  • Gene Expression Profiling
  • Granulosa Cells / metabolism*
  • Inhibin-beta Subunits / metabolism*
  • Inhibins / metabolism*
  • RNA Interference
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Theca Cells / metabolism*

Substances

  • Androgens
  • inhibin beta A subunit
  • inhibin-alpha subunit
  • Inhibins
  • Inhibin-beta Subunits