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49: Continuous infusion with with 17-Hydroxyprogesterone Caproate (17-P) into the fetal or maternal arterial circuits of the ex vivo placental cotyledon model attenuates vasoconstriction by thromboxane and angiotensin-II

      Objective

      Weekly injections of 17-Hydroxyprogesterone Caproate (17-P) has been shown to reduce the recurrence rate of preterm deliveries. Our prior research has shown that bolus injections of 17-P into the fetal-placental arteries reversed vasoconstriction caused by the continuous infusion of thromboxane. Our objectives were to determine if a continuous infusion of 17-P into the fetal-placental arteries would attenuate the vaso-active effects of bolus doses of thromboxane and angiotensin-II and also if a continuous infusion of 17-P into the maternal side of the cotyledon would have a similar effect.

      Study Design

      Two cotyledons were obtained from each of five placentas at the time of cesarean section. A chorionic artery and vein pair were cannulated in each cotyledon and perfused with a balanced Hank′s and albumin solution. After thirty minutes, one of the cotyledons was randomly chosen and switched to a continuous infusion of a perfusate containing 17-P. Next, vasoconstricting doses of thromboxane followed by angiotensin-II were injected into each cotyledon′s artery and serial perfusion pressures were measured for an additional thirty minutes. This experiment was then repeated on a different set of placentas, perfusing the 17-P continuously into the maternal circulation instead of the fetal arteries.

      Results

      The continuous infusion of 17-P did not change the perfusion pressure relative to the control cotyledon. Bolus injections of thromboxane and angiotensin-II increased the perfusion pressure of both the 17-P and the control cotyledons but the increase in pressure was significantly less (p < 0.05) in the 17-P treated cotyledons.

      Conclusion

      Continuous 17-P infusion into either the fetal or maternal arterial circuits of a placental cotyledon attenuates thromboxane and angiotensin-II induced vasoconstriction in human placentas. To our knowledge, this is the first study to demonstrate that continuous perfusion of the maternal placental circulation with 17-P attenuates vasoactive effects of the fetal placental arteries.