Vascular reactivity to angiotensin II and eicosanoid production in the human placenta from term and preterm pregnancy

Isolated human placental cotyledons from normal term (37-40 weeks of gestat ion) and preterm (26-36 weeks of gestation) labor were perfused in vitro, a nd the effect of angiotensin Il (ANG II) and its interaction with prostanoi ds was measured. In the preterm group, ANG II caused greater maximal increa ses in perfusion pressure than in normal term pregnancies without affecting sensitivity. Also, preparations from normal term pregnancies showed a mark ed development of tachyphylaxis compared to placentae from preterm pregnanc ies. Indomethacin (10(-6) M) increased the maximum pressor response to ANG II by 33.6% in normal term, however, in preterm placentas a 39.2% reduction was observed. Infused ANG parallel to 10(-6) M > decreased the concentrati ons of thromboxane B-2 and 6-keto-PGF(1 alpha) in both pregnancy groups, bu t this effect was not statistically different from the baseline values. In the current study, we show that the placenta of preterm pregnancies in basa l conditions produce 7.6 times as much thromboxane as the normal term place nta (2,800 +/- 470 vs, 366.5 +/- 62 pg/min, respectively), without signific ant change in prostacyclin levels (preterm 88.6 +/- 11.0 vs. Term 100.6 +/- 30.7 pg/min). These observations provide evidence that the contribution of basally released thromboxane from placental tissue appears to contribute t o abnormalities in the regulation of fetoplacental hemodynamics in prematur e pregnancies. Copyright (C) 2000 S. Karger AG, Basel.