Interrelationships Between Oxytocin and Eicosanoids in Human Fetal Membranes at Term Gestation: Which Role for Leukotriene B4?

Abstract

The existence of a functional paracrine loop between oxytocin and prostaglandin F2-α in human placental cells has been demonstrated. The present study was undertaken to investigate further the possible interrelationships between oxytocin and eicosanoids in human intrauterine tissues at term gestation. Therefore, we evaluated the effect of leukotriene B4 (LTB,4) on oxytocin (OT) production by explants of fetal membranes and amnion and the effect of oxytocin on the production ofLTB4 and prostaglandin E2 (PGE2) by both fetal membranes and amnion. In all cases studied (n=25), short-term cultures of tissue explants fetal membranes or amnion) have been carried out. The production of eicosanoids and oxytocin in culture medium was evaluated. Oxytocin measurement was carried out by radioimmunoassay following extraction of the substance with Sep Pak C18 cartridges, PGE2 and LTB4 were measured by radioimmunoassay directly in culture medium. Results show that LTB4 has no significant stimulatory effect on oxytocin production by fetal membranes or amnion tissue. On the other hand, oxytocin stimulates PGE2 release by both fetal membranes and isolated amnion, but has no effect on LTB4 production by these tissues. Taken together, these findings suggest the following conclusions: (1) a paracrine loop between LTB4 and oxytocin is lacking in fetal membranes and amnion at term pregnancy; (2) oxytocin exerts a stimulatory effect on PGE2 release by both fetal membranes and amnion; (3) the interrelationships between oxytocin and the different eicosanoids in the above tissues seem to be highly selective.