Effects of the fetal-placental unit on uterine prostaglandin levels at term in the pregnant rat

Abstract

Uterine prostaglandins (PGs) increase markedly at term in the pregnant rat. To assess the contribution of the fetal-placental unit (FUP) on uterine tissue and uterine venous blood PG concentrations, each uterine horn of 14 unilaterally pregnant rats at day 21 of pregnancy were compared. In addition, 7 bilaterally pregnant rats were studied. Uterine tissue and uterine venous plasma PGF, PGE, 6-Keto-PGF 1 (6KF) and thromboxane B 2 (TxB 2) and systematic plasma progesterone, estradiol and estrone were determined by radioimmunoassay. Uterine concentrations of PGs (ng/mg DNA) were always greater on the pregnant side of unilaterally pregnant rats (p<.05) although the PGF levels were elevated to a lesser extent than were PGE, TxB 2 or 6KF. However, no differences were detected between uterine tissue from the pregnant side of unilaterally pregnant compared to bilaterally pregnant rats. In addition, no differences were found in uterine venous plasma PGs adjacent or opposite the pregnant uterine horn and in systematic plasma progesterone, estradiol and estrone levels in unilaterally vs bilaterally pregnant rats. These data suggest that the presence of the FPU is associated with an increased capacity of uterine tissue to produce PGE, TxB 2 and 6KF, and to a lesser degree PGF, and thus may contribute to the increase in uterine PGs periparturition.