Effect of exogenous prostacyclin on central and uterine hemodynamics in the chronically instrumented pregnant guinea pig before and after indomethacin administration

Mechanisms regulating angiotensin II responsiveness by the uteroplacental circulation

Pregnancy is associated with increases in cardiac output and uterine blood flow (UBF) and a fall in systemic vascular resistance. In ovine pregnancy, UBF rises from approximately 3% of cardiac output to approximately 25% at term gestation, reflecting a >30-fold rise in UBF by term. This increase in UBF supports exponential fetal growth during the last trimester and maintains fetal well-being by providing excess oxygen and nutrient delivery. These hemodynamic changes are associated with numerous hormonal changes, including increases in placental steroid hormones and enhanced activation of the renin-angiotensin and sympathetic nervous systems, all of which are believed to modulate systemic and uterine vascular adaptation and vascular reactivity. Systemic pressor responses to infused ANG II are attenuated in normotensive pregnancies and the uteroplacental vasculature is even less sensitive, suggesting development of mechanisms to maintain basal UBF and permit the rise in UBF necessary for fetal growth and well-being. The effects of ANG II on the uteroplacental vasculature are reviewed, and the mechanisms that may account for attenuated vascular sensitivity are examined, including ANG II metabolism, vascular production of antagonists, ANG II-receptor subtype expression, and the role of indirect mechanisms.

Plasma prostacyclin and thromboxane concentrations in 160 normotensive, hypotensive, and preeclamptic patients during pregnancy, delivery, and the post partum period

Plasma concentrations of 6-keto-prostaglandin F1 alpha, a stable metabolite of prostacyclin, and TxB2 were measured in 160 women during pregnancy (n = 106), delivery (n = 40), and in the postpartum period (n = 14). Fifty nine patients had normal blood pressure, 10 had mild and 9 severe preeclampsia while 38 patients were hypotensive. Normotensive patients were grouped according to their gestational age: 22-26 weeks (n = 22), 27-31 weeks (n = 22), and 32-38 weeks (n = 15). 20 patients were in early first stage of delivery (cervical dilatation < or = 5 cm), 20 patients in late first stage (cervical dilatation > or = 6 cm). The concentration (mean value +/- SEM) of the PGI2 metabolite tended to increase during pregnancy without reaching significance (218 +/- 11; 225 +/- 10; 250 +/- 15 pg/ml). At the same time, TxB2 showed a decrease, which was most pronounced at 27-31 weeks (65 +/- 15; 40 +/- 2; 48 +/- 4 pg/ml; p < 0.001). The ratio of PGI2/TxA2 increased in parallel (4.9 +/- 0.4; 6 +/- 0.4; 4 +/- 0.5). There was no difference in plasma concentrations of PGI2 (figure 4) and TxA2 in patients with normal blood pressure, mild preeclampsia and hypotension, whereas in severe preeclampsia, the plasma concentration of PGI2 was significantly lower (p < 0.001) and of TxA2 significantly higher (p < 0.001). The ratio of PGI2/TxA2 shifted significantly to vasoconstriction in patients with severe preeclampsia (p < 0.0001) and to vasodilatation in those with hypotension (p < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)