Inhibition of oxytocin receptor and estrogen receptor-alpha expression, but not relaxin receptors (LGR7), in the myometrium of late pregnant relaxin gene knockout mice

Endocrinology. 2003 Oct;144(10):4272-5. doi: 10.1210/en.2003-0548. Epub 2003 Jul 24.


This study used relaxin (RLX) gene knockout mice (Rlx-/-) to investigate the effects of RLX on myometrial oxytocin receptor (OTR) and estrogen receptor (ER)-alpha gene expression in late gestation. We also characterized the temporal expression of the RLX receptor (LGR7) and demonstrated gene transcripts in the myometrium of Rlx+/+ and Rlx-/- mice. There was a significant (P < 0.05) decrease in myometrial LGR7 gene expression on d 17.5 and 18.5 post coitum (pc) compared with earlier stages of gestation, but no differences between Rlx+/+ and Rlx-/- mice. Myometrial OTR mRNA levels increased at the end of gestation in Rlx+/+ but not Rlx-/- mice. ERalpha gene expression was up-regulated on d 14.5 pc in Rlx+/+ mice, with mRNA levels remaining high throughout late gestation. In contrast, ERalpha mRNA levels were significantly lower in Rlx-/- mice on d 14.5 and 18.5 pc. These data show that the increases in myometrial OTR and ERalpha expression in late pregnant Rlx+/+ mice were attenuated in Rlx-/- mice. The effects of RLX on OTRs are probably mediated via activation of ERalpha. Finally, RLX receptor expression in the myometrium of Rlx-/- mice did not differ from wild-type mice, implying that RLX does not influence expression of its receptor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Estrogen Receptor alpha
  • Female
  • Gestational Age
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout / genetics
  • Myometrium / metabolism*
  • Pregnancy
  • Pregnancy, Animal / metabolism*
  • RNA, Messenger / metabolism
  • Receptors, Cell Surface / metabolism*
  • Receptors, Estrogen / antagonists & inhibitors*
  • Receptors, Estrogen / genetics
  • Receptors, G-Protein-Coupled
  • Receptors, Oxytocin / antagonists & inhibitors*
  • Receptors, Oxytocin / genetics
  • Relaxin / deficiency*
  • Relaxin / genetics


  • Estrogen Receptor alpha
  • RNA, Messenger
  • RXFP1 protein, mouse
  • Receptors, Cell Surface
  • Receptors, Estrogen
  • Receptors, G-Protein-Coupled
  • Receptors, Oxytocin
  • Relaxin