HELLP (hemolysis elevated liver enzyme low platelet) syndrome is associated with hypertension, inflammation, oxidative stress and endothelial activation. The objective of this study was to determine if oxygen scavenging or endothelin A receptor antagonism improved hypertension and oxidative stress. sFlt-1 and sEndoglin were infused via mini-osmotic pump into normal pregnant rats (NP) on gestational day 12 to create HELLP syndrome. On gestational day 18 arterial catheters were inserted and on gestational day 19 mean arterial pressure was analyzed in rats; serum, urine and tissues were collected for molecular analysis. HELLP rats had significantly increased MAP compared to control normal pregnant rats (P<0.0005). Endothelin A receptor antagonism via ABT-627 and Tempol, superoxide dismutase mimetic, were administered to a subset of normal pregnant and HELLP rats beginning on gestational day 13 and attenuated mean arterial pressure in HELLP rats (P<0.05; P<0.005). There were no statistically significant differences in mean arterial pressure between NP+ETA Receptor or NP+Tempol treated rats and NP rats (P=0.22). Endothelin A receptor blockade significantly decreased HELLP induced isoprostane excretion (P<0.0005), placental and hepatic reactive oxygen species (P<0.05; P<0.0005) and increased placental total antioxidant capacity (P<0.005) compared to untreated HELLP rats. Similar results in isoprostane (P<0.005), hepatic reactive oxygen species (P<0.05) and placental total antioxidant capacity (P<0.05) were seen in HELLP rats treated with Tempol or Endothelin A receptor antagonist vs. untreated HELLP rats. These data demonstrated a role for oxidative stress in contributing to the hypertension, placental and liver damage that is seen in HELLP syndrome.