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.

Key Words:

• Oxytocin
• Leukotriene B4
• Prostaglandin E2
• Fetal Membranes