OXYTOCIN IN HUMAN INTRAUTERINE TISSUES AT PARTURITION

The recent detection of oxytocin (OT) mRNA in human gestational tissue s suggests that OT may be locally synthesized and released to act on t he uterus as a local mediator in the mechanism of parturition. In orde r to investigate this possibility the OT immunoreactive (I.R.) content was examined directly in placental decidua and amniochorial membranes after term and preterm delivery and in their culture media at term ge station. I.R.OT concentrations were also measured in maternal, retropl acental and umbilical plasma as well as in amniotic fluid in the prese nce or the absence of labour. Low I.R.OT concentrations (below 15 fmol g(-1) wet tissue) were found in both amniochorial membranes and place ntal decidua. Moreover, whereas in amniochorion they were higher (P < 0.05) after preterm than term spontaneous parturition, in decidua they were higher (P < 0.05) after term than preterm vaginal delivery. Dete ctable amounts (below 15 fmol g(-1) wet tissue per h) of I.R.OT were a lso found in culture media from explants of the above tissues. Among a ll the examined maternal and fetal fluids a rise in I.R.OT content at parturition was detected only in the amniotic liquor (P < 0.05). These findings suggest that I.R.OT concentrations in intrauterine tissues a re very low; however, considering that OT is the most potent endogenou s uterotonic agent, OT at such concentrations might play a paracrine f unction in the biochemical events leading to human parturition. Theref ore, a role for amniotic OT in parturition can not be excluded.