Distribution of prostaglandin endoperoxide synthase and prostacyclin synthase in the late pregnant uterus

Abstract

Prostacyclin (PGI2) synthase and prostaglandin endoperoxide synthase (cyclo-oxygenase; PGH synthase) were measured with specific immunoradiometric assays in myometrial microsomes from different areas of a primigravid uterus at 34 weeks gestation. PGH synthase concentrations increased significantly from fundus toward lower segment (P less than 0.005), but that trend did not apply to PGI2 synthase concentrations, which were significantly higher on the placental than on the non-placental side of the uterus (P less than 0.005). PGI2 synthase concentrations showed no further increase with increasing proximity to the placental bed. In myometrium underneath the placental bed there was an inverse relation between the PGH and PGI2 synthase concentrations (r = 0.86; P less than 0.01) which did not apply to other regions of the uterus. The data suggest that local rather than general mechanisms control uterine PGH and PGI2 synthase concentrations, and that uterine prostaglandin and PGI2 production strongly depend on anatomical relations that have been neglected in previous studies on uterine prostaglandin biosynthesis.