Fetal, neonatal cord, and maternal plasma concentrations of angiotensin‐converting enzyme (ACE)

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Abstract
Objectives: Angiotensin‐converting enzyme (ACE), a component of the renin–angiotensin system (RAS), catalyses the degradation of angiotensin I to angiotensin II. It was the aim of the present study to measure ACE activity in human fetal blood and to determine its changes with advancing gestational age.Methods: Fetal blood was sampled by cordocentesis from six control fetuses and six fetuses with Rh isoimmunisation. Cord blood was sampled from six preterm neonates, 15 neonates after spontaneous delivery at term and six neonates at term after caesarean section. In addition, maternal ACE values were determined. ACE activity was measured using the miniaturised fluorimetric method.Results: In normal fetuses (13.31±1.41 nmol HL/min/ml) and fetuses with Rh isoimmunisation (13.08±2.00 nmol HL/min/ml) ACE activity was significantly higher than in corresponding maternal plasma (10.39±0.93 nmol HL/min/ml, p<0.05). Neonatal cord blood of preterm newborns (10.43±0.69 nmol HL/min/ml) and term newborns (8.99±0.49 nmol HL/min/ml) showed a significantly decreased ACE activity compared to the fetal controls.Conclusion: We conclude that the high fetal ACE activity and the stringent regulation with advancing gestational age indicate the physiological importance of the enzyme during prenatal development. Copyright © 2002 John Wiley & Sons, Ltd.