Oxytocin-induced phasic and tonic contractions are modulated by the contractile machinery rather than the quantity of oxytocin receptor

Masaki Kawamata, Yutaka Tonomura, Tadashi Kimura, Yukihiko Sugimoto, Teruyuki Yanagisawa, Katsuhiko Nishimori

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

To investigate the relationship between the oxytocin (OT) receptor (OTR) quantity and the contractile features systematically, we measured the mRNA expression levels of OTR and L-type Ca2+ channel α 1C-subunit (α1C) and examined the regulatory mechanisms of OT-induced phasic or tonic contractions of the longitudinal smooth muscles in mouse uteri. The mRNA expression of OTR in 19.0 G (19.0 days of gestation) was greater than those in nonpregnant phases, and that of α1C in estrus and 19.0 G was higher than in diestrus. OT-induced contractions sparsely occurred in diestrus. The OT-induced all-or-none-type phasic contractions at low concentrations were abolished by verapamil in both estrus and 19.0 G. OT-induced tonic contractions had similar pD2 values in both estrus and 19.0 G. However, the magnitude in 19.0 G was much greater than that in estrus. The large tonic contractions also occurred in PGF receptor (FP) knockout mice in 19.0 G despite a small amount of OTR. Verapamil and Y-27632 partially inhibited the tonic contractions in 19.0 G. Cyclopiazonic acid-induced tonic contractions were reciprocally decreased with the increase in the OT-induced ones in 19.0 G. These results indicate that the phasic contractions are dependent on α1C. The tonic contractions in 19.0 G are dependent on both Ca2+ influxes via L-type Ca2+ channels and store-operated Ca2+ channels, and the force is augmented by the Rho signal pathway, which increases the Ca2+ sensitivity. Thus the uterine contractions are mainly controlled by the modification of contractile signal machinery rather than simply by the OTR quantity.

Original languageEnglish
Pages (from-to)E992-E999
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume292
Issue number4
DOIs
Publication statusPublished - 2007 Apr

Keywords

  • Contraction
  • Mouse
  • Oxytocin
  • Receptor quantity
  • Uterus

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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