Transplacentally‐Administered Enalapril Inhibits the Spontaneous Constriction of the Ductus Arteriosus in the Newborn Rat

ABSTRACT Pregnant Wistar rats were given orally enalapril maleate (EM), an angiotensin‐converting enzyme (ACE) inhibitor, 15–60 min prior to Caesarean operation and the diameter of the ductus arteriosus (DA) in the newborn rats was calibrated at intervals after delivery. The caliber of the DA in control newborn rats gradually decreased to less than 10% of the initial value by 90 rnin after delivery. The DA calibers of the newborn rats treated with 50 or 200 mg/kg EM in utero were larger than the controls at any time interval up to 90 rnin and the difference from the control value was significant for at least 30 rnin after delivery when the drug was given to the dam 30 rnin prior to Caesarean section. The present study has demonstrated that transplacentally‐administered enalapril inhibits the spontaneous constriction of the neonatal rat DA and supports the view that ACE inhibitors should not be used late in pregnancy.