Metabolism of prostaglandin F2 alpha in the fetal circulation of the human term placenta in vitro.

The metabolism of prostaglandin F2 alpha (PGF2 alpha) was investigated in the fetal cotyledons of human term placentas by an in vitro perfusion technique. When 80 nmol of 14C-PGF2 alpha was infused in 2 min into the chorionic artery, 56 +/- 7% (mean +/- SEM, n = 7) of the infused radioactivity appeared in the nonrecirculating venous effluent in 6 min. Most of this radioactivity was as unmetabolized PGF2 alpha. Only 12 +/- 2% of the radioactivity in this venous effluent was as metabolites, the major metabolite being 13,14-dihydro-15-keto-PGF2 alpha. During the following 2 min, 2 +/- 1% of the infused radioactivity appeared in the venous effluent. The fluid trickling through the decidual plate contained 5 +/- 1% of the infused radioactivity. After the perfusion 10-15% of the infused radioactivity was retained in the tissue, being mainly as 13,14-dihydro-15-keto-PGF2 alpha. The oxygen consumption of the tissue was 0.4 +/- 0.1 ml/100 g/min, which is adequate for vital placenta tissue. The study suggests that the metabolism of PGF2 alpha is negligible in the fetal circulation of the human term placenta.