Comparison and correlation of serum and placental levels of angiotensin-converting enzyme (ACE) and nitric oxide (NO) in preeclampsia

Preeclampsia (PE) is a pregnancy-exclusive multi-system disorder complicating 5-7% of pregnancies and is one of the leading causes of feto-maternal morbidity and mortality worldwide. It is characterized as hypertension (>140/90mm Hg) after 20 weeks’ gestation, accompanied by proteinuria (>300 mg/l). Without sufficient changes in the uterine vasculature in early pregnancy, the placenta may become hypoxic with advancing gestation and suffer from oxygen deficiency at the tissue levels, and the supply of both nutrients and oxygen to the fetus is disturbed. Altered renin-angiotensin-aldosterone pathway metabolites- including angiotensin-converting enzyme (ACE) - generated within placental tissue, contribute to increased vasoconstriction, increase in tissue hypoxia and consequent lipid peroxidation seen in preeclampsia. This, in turn, could lead to a decrease in nitric oxide (NO) levels in the placental tissue, causing further vasoconstriction.

A similar mechanism, if occurring in the maternal circulation as well, could further explain the systemic vascular dysfunction observed in this condition. The aim of this study is to estimate the placental levels of ACE and NO, and serum levels of ACE and NO and compare them with an aim to elucidate the pathophysiology of preeclampsia.

The study will be carriedout in the Department of Biochemistry, KMC, MAHE. Ethicalclearance was obtained from the Institutional Ethical Committee (IEC), following which 124 leftover bloodsamples will be collected after obtaining consent from subjects. Placentaltissue samples will be collected from the same subjects following delivery. ACEwill be measured in the serum and placental tissue homogenate usingHippuryl-Histidyl-Leucine (HHL) as substrate by a method modified from Cushmanand Cheung. NO will be estimated in serum and placental homogenate using Griessreagent.