Uptake, transfer and metabolism of prostaglandin E2 in the isolated perfused human placental cotyledon

( 3 H) PGE 2 uptake and transfer in the isolated perfused human placental cotyledon was assessed by a ingle pass paired isotope dilution technique utilising ( 14 C) sucrose as an extracellular marker. Metabolism of ( 3 H) PGE 2 was measured by analysing maternal and fetal effluents from perfused human placental cotyledons after bolus injection of ( 3 H) PGE 2 into ither the maternal or fetal sides. Maximal uptake of ( 3 H) PGE 2 was greater on the maternal (81 +/- 8%) than the fetal sides (42 +/- 12%) and showed saturation with increasing concentrations of PGE 2 only on the fetal side with an apparent Km of 12 +/- 4.9 nmol/l and v max of 1.5 +/- 0.2 pmol/min/g. Total recoveries of ( 3 H) PGE 2 were 84.6 +/- 11.8 % and 32.6 +/- 6.3 % of the injected dose after injection on the fetal and maternal sides respectively.Transferof ( 3 H) PGE 2 was the same in both directions being 6.4 +/- 1.2 % of the injected dose in the fetal-maternal direction and 5.8 +/- 2.7 % of the injected dose in the maternal-fetal direction. Metabolism was greater on the maternal side (35% of injected ( 3 H) PGE 2 ) thanthe fetalside(18% of injected ( 3 H) PGE 2 ) and was principally to the 13,14-dihydro-15-keto-PGE 2 metabolite. Metabolism of ( 3 H) PGE 2 after passage across the placenta was the same in both directions and was of the order of approximately 60%.