Figure 3.

Main actions of the ‘new’ renin-angiotensin system (RAAS) during pregnancy and preeclampsia in (a) the circulating system and (b) the uteroplacental unit. (a) In normal pregnancy the renin-angiotensin system is up regulated and contributes to the establishment of plasma volume expansion. The balance between circulating A1-7 and angiotensin II favours vasodilation. In pre-eclampsia the renin-angiotensin system is down regulated. Relatively low A1-7 levels in the presence of AT1-AA and increased AT1-receptor sensitivity may result in a shift favouring vasoconstriction.(b) In normal pregnancy both A1-7 and angiotensin II contribute to the regulation of trophoblast invasion and angiogenesis. In pre-eclampsia, over activation of the AT1-receptor in the uteroplacental unit by AT1-AA or angiotensin II may cause the release of pathogenic substances, leading to impaired placentation and reduced placental blood flow