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  • Title: In vivo dilatation of the fetal and postnatal ductus arteriosus by inhibition of phosphodiesterase 3 in rats.
    Author: Toyoshima K, Momma K, Imamura S, Nakanishi T.
    Journal: Biol Neonate; 2006; 89(4):251-6. PubMed ID: 16319452.
    Abstract:
    BACKGROUND: Clinically, it appears that phosphodiesterase 3 (PDE 3) inhibitors, which are used for acute cardiac failure in premature infants, dilate the ductus arteriosus (DA). OBJECTIVES: To clarify the ductus-dilating effects of PDE 3 inhibitors in near-term rat pups and their differential effects in near-term and preterm fetal rats, in in vivo studies. METHODS: The in vivo ductal diameter of rat pups and fetuses was measured using a rapid whole-body freezing method, by cutting on a freezing microtome and measuring with a microscope and micrometer. Eight to twenty pups and fetuses were studied in each group. Milrinone and amrinone (specific inhibitors of PDE 3) were injected into 1-hour-old pups and the DA was studied 0.5 and 1 h later. The differential effects of these PDE 3 inhibitors on the near-term and preterm ductus were studied by injecting indomethacin (10 mg/kg) and PDE 3 inhibitors into 21D (21st day of pregnancy: term-21.5 days) and 19D dams and studying the fetal ductus 4 and 8 h later. RESULTS: Milrinone and amrinone dilated the postnatal ductus dose-dependently. Large doses of these drugs dilated it completely, and clinically equivalent doses dilated it minimally. Milrinone and amrinone prevented constriction of the fetal ductus by indomethacin. Their ductus-dilating effects were more potent in the preterm than in the near-term fetuses, and clinically equivalent doses of these PDE 3 inhibitors dilated preterm ductus completely. CONCLUSION: In rats, PDE 3 inhibitors reopen the constricted postnatal DA slightly. PDE 3 inhibitors dilate the fetal DA constricted with indomethacin effectively and more sensitively in preterm than in near-term fetuses.
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