Brown Norway (BN) and Lewis (LW) inbred rat strains harbor different angiotensin-converting enzyme ( Ace) polymorphisms that result in higher ACE activity in BN than LW rats. Thus we hypothesized that pregnant BN rats would show pregnancy complications linked to angiotensin II (AII) activity. We performed longitudinal and cross-sectional studies in pregnant LW and BN rats. We found that BN rats have significantly higher ACE activity and AII levels at prepregnancy and throughout pregnancy compared with LW rats, except at midgestation. BN placentas and maternal kidneys had significantly higher expression of AII receptor 1 (AGTR1) and lower expression of AGTR2 than the respective LW placentas and maternal kidneys. Renin-angiotensin system activation in BN rats correlated with hypertension and proteinuria at gestational days 17-21, which were resolved after delivery. In addition, BN rat pregnancies were characterized by significant fetal loss, restricted growth in surviving fetuses, decreased uteroplacental blood flows, and decreased trophoblast remodeling of uterine arteries compared with LW pregnancies. Short-term losartan treatment significantly increased uteroplacental blood flow and fetal weight and decreased maternal blood pressure (BP) and proteinuria in BN pregnancies. In contrast, losartan treatment significantly decreased uteroplacental blood flow and fetal weight but had no significant effect on maternal BP in LW pregnancies. We conclude that Ace polymorphisms play an important role in the reproductive phenotype of BN and LW rats and that BN rats are a novel model of pregnancy complications in association with genetically controlled, increased ACE activity.

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