P C Johnston1, I A Greer, A N Brooks. 1. Department of Obstetrics and Gynecology, University of Glasgow, Royal Infirmary, Scotland.
Abstract
OBJECTIVE: This study investigated whether prostaglandin E2 (PGE2) can cross intact fetal membranes in vivo. METHODS: We have developed a novel ovine model using in vivo dialysis systems, positioned between the fetal membranes and decidua and in the amniotic cavity. Sheep were given 25 microCi, 50 ng [3H]PGE2 or 1 mg PGE2 to the amniotic cavity, and radioactivity or PGE2/PGEM concentrations in dialysates were determined. RESULTS: Endogenous basal PGE2 concentrations were significantly higher in extra-amniotic than in intra-amniotic dialysates (715 +/- 436 versus 80 +/- 31 pg/mL; mean +/- standard error of the mean; P < .05). After injection of [3H]PGE2 into the amniotic cavity, no radioactivity was detected in the extraamniotic dialysate, and this was not influenced by labor induced by ACTH administration to the fetus. In contrast, intra-amniotic injection of 1 mg PGE2 resulted in marked transfer of PGE2 across the fetal membranes to the extra-amniotic dialysis system. CONCLUSION: These results suggest that PGE2 can cross the ovine fetal membranes in vivo, escaping metabolism in the chorion.
OBJECTIVE: This study investigated whether prostaglandin E2 (PGE2) can cross intact fetal membranes in vivo. METHODS: We have developed a novel ovine model using in vivo dialysis systems, positioned between the fetal membranes and decidua and in the amniotic cavity. Sheep were given 25 microCi, 50 ng [3H]PGE2 or 1 mg PGE2 to the amniotic cavity, and radioactivity or PGE2/PGEM concentrations in dialysates were determined. RESULTS: Endogenous basal PGE2 concentrations were significantly higher in extra-amniotic than in intra-amniotic dialysates (715 +/- 436 versus 80 +/- 31 pg/mL; mean +/- standard error of the mean; P < .05). After injection of [3H]PGE2 into the amniotic cavity, no radioactivity was detected in the extraamniotic dialysate, and this was not influenced by labor induced by ACTH administration to the fetus. In contrast, intra-amniotic injection of 1 mg PGE2 resulted in marked transfer of PGE2 across the fetal membranes to the extra-amniotic dialysis system. CONCLUSION: These results suggest that PGE2 can cross the ovine fetal membranes in vivo, escaping metabolism in the chorion.