The direct influence of the embryo on uterine PGF2 and PGE2 production in sheep

Abstract

In unilateral pregnant ewes, obtained by surgically transecting one uterine horn to isolate it from the rest of the pregnant uterus, the isolated horn develops endometrial oxytocin receptors by day 16 despite being in a hormonal environment equivalent of that of a pregnant ewe. This study examines uterine prostaglandin production in these animals. On day 16 of pregnancy, ewes were anaesthetized and a uterine vein draining each horn and the jugular vein cannulated. Venous blood samples were taken at 10 min intervals for 1 h before and 1 h after an i.v. injection of oxytocin (1 microgram). Uterine vein samples were assayed for PGF2 alpha and PGE2 and jugular blood samples assayed for 13,14-dihydro,15-keto-PGF2 alpha. All ewes showed high plasma concentrations of 13,14-dihydro,15-keto-PGF2 alpha after the oxytocin injection. PGF2 alpha increased in the uterine vein draining the nonpregnant transected horn of a unilaterally pregnant ewe following oxytocin treatment, whereas there was no increase in concentration in plasma draining the pregnant horn. Basal plasma PGF2 alpha concentrations from the uterine vein draining the pregnant horn were significantly higher than concentrations obtained from the uterine vein of the transected horn while PGE2 concentrations did not vary between the two horns. After oxytocin injection, there was a significant increase in plasma PGE2 concentration in venous blood collected from both sides.(ABSTRACT TRUNCATED AT 250 WORDS)