• Cytokines;
  • estrogen;
  • parturition;
  • progesterone

PROBLEM: Little is known regarding the regulation of the timing of parturition. Recent evidence suggests an interaction between the immune system and uterine contractility in late gestation. METHOD: Pregnant rats were treated with LPS in vivo in attempts to establish a model of premature parturition induced by the pro-inflammatory response. Uterine explants were incubated in vitro to determine the effects of IL-6 on uterine synthesis of oxytocin (OT) and its receptor (OTR). RESULTS: LPS injection was quite toxic to pregnant rats and gave extremely variable results. In animals that delivered, there was a marked increase in the uterine concentrations of OTR and OTR mRNA. There was no consistent effect regarding the timing of parturition. IL-6 caused a significant increase in the concentration of OTR mRNA in uterine explants from pregnant rats but not in tissues from non-pregnant animals. CONCLUSION: Rat uterine concentrations of OTR are regulated by IL-6. Pro-inflammatory cytokines may stimulate uterine contractility in late gestation rat uterine tissues through a mechanism involving stimulation of OTR.