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20: Improvement of uterine artery resistive index and blood pressure in response to an Endothelin type A receptor antagonist in a rat model of preeclampsia

      Objective

      To determine the effect of an Endothelin type A receptor antagonist (ETA) on uterine artery resistive index (Ut RI) and blood pressure in a rat model of placental ischemia produced by Reduction in Uterine Perfusion Pressure (RUPP).

      Study Design

      Power Doppler velocimetry measurements were performed on anesthetized pregnant Sprague Dawley rats with a Vevo 770 unit using a 30 MHz transducer and an insonating angle <30°. Ut RI was determined for the uterine artery bilaterally at three levels and the mean Ut RI was calculated. Ut RI was measured in the RUPP and normal pregnant controls (NP) on gestation days (GD) 12, 15 and 18. Ut RI was also determined on GD 18 in NP and RUPP dams after pretreatment with ETA. RUPP procedure was done on GD 14 with chronic constriction of the lower abdominal aorta above the iliac bifurcation (0.203 mm clip) and both ovarian arteries (0.100 mm clip). Pregnant dams treated with ETA received the agent in their drinking water (5mg/Kg/day) on GD 12 -19. The rats were instrumented with a carotid catheter for mean arterial pressure measurement (MAP) on GD 19.

      Results

      Ut RI in NP and RUPP groups were 0.59+/−0.02 vs. 0.57+/−0.01 (P = 0.423), 0.60+/−0.02 vs. 0.71+/−0.02 (P = <0.001) and 0.54+/−0.03 vs. 0.67+/−0.02 (P = <0.001) on GD 12, 15 and 18 respectively. MAP in the NP and RUPP groups were 104+/−1 and 129+/−2 mm Hg, respectively (P = <0.001). Pretreatment with ETA attenuated both the MAP and GD 18 Ut RI in the RUPP group (115+/−1 mm Hg (P = <0.001); 0.58+/−0.02 (P = <0.001)) without affecting these parameters in the NP group (98+/−2 mm Hg (P = 0.054); 0.55+/−0.02 (P = 0.150)).

      Conclusions

      The improvement in uterine artery resistive index could be one potential mechanism for the reduction in blood pressure in response to an Endothelin type A receptor antagonist in placental ischemic pregnant rats.
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