Changes in the concentrations of prostaglandins E and F in the utero-placental tissues of late pregnant rabbit after the administration of oxytocin or prostaglandin F2 alpha

We have investigated the effects of exogenous oxytocin and prostaglandin F2 alpha (PGF2 alpha) on the concentrations of prostaglandins E and F (PGE and PGF) in the utero-placental tissues in late pregnant rabbit. The subjects were 5 rabbits each on days 26, 27 and 30 of pregnancy. After one side of the uterine horn was excised as the control, 3,000 micrograms of PGF2 alpha, 10 microU of oxytocin or 1 ml of saline was administered to 2,2 and 1 rabbits as an iv bolus dose. After 10 minutes, the remaining side of the uterine horn was excised. The myometrium, fetal and maternal cotyledon, decidua and amnion were separated. The concentrations of PGE and PGE in each tissue were measured by radioimmunoassay after extraction. The highest concentration of PGE was observed in the fetal cotyledon and that of PGF in the decidua. The amniotic PGE concentration significantly decreased after the administration of both oxytocin and PGF2 alpha. The myometrial PGF concentration increased significantly after the administration of PGF2 alpha, and the degree of the increase in PGF became greater as pregnancy advanced. However, the myometrial PGF concentration did not increase after the administration of oxytocin.