Oxytocin receptor blockade and prostaglandin release in late pregnant sheep

Abstract

The oxytocin receptor inhibitor 1-deamino-2- d-Tyr-(oET)-4-Thr-8-orn-oxytocin (CAP) was infused into late pregnant sheep. Basal and oxytocin-induced prostaglandin (PG) concentrations in maternal and fetal plasma were determined. CAP had no significant effect on maternal PGFM or PGE 2 or fetal PGF 2α, PGFM or PGE 2 concentrations during late pregnancy or at term. PGF 2α was not detectable in maternal peripheral plasma. CAP infusion did not affect fetal well-being. Oxytocin injection to the mother caused a significant, dose-dependent, increase in maternal plasma PGFM concentrations but did not alter maternal PGE 2 concentrations or fetal PGF 2α and PGE 2 concentrations. The increase in maternal PGFM concentrations brought about by oxytocin injection was decreased during intrauterine infusion of CAP over the range of 12.5–100 μ/min. A rationale for the use of oxytocin receptor blockade for the prevention of premature labor is thus provided.