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ABSTRACT _Extract_: Development of the constrictor response of the ductus arteriosus to O2 and selected vasoactive drugs (acetylcholine and bradykinin) was studied in 20 fetal lambs weighing
680–4800 g (90− to 150-day gestation). The isolated ductus arteriosus was perfused _in vitro_ with Tyrode's solution at constant flow, temperature (38°), pH (7.3–7.4), and P CO 2
(30–40 mm Hg), and the mean pressure difference across the ductus was measured. Ductal resistance was calculated at different levels of P O 2 (10–700 mm Hg), raised stepwise to produce
dose-response curves. Three young fetuses failed to respond initially to O2 and in the other 17 the initial response occurred at progressively lower P O 2 levels with advancing gestation.
The maximal degree of constriction developed showed a progressive increase with advancing gestational age. At any given P O 2 , both acetylcholine and bradykinin produced a further increase
in resistance when added to the perfusion solution, but this further increase was independent of age. The level of P O 2 at which an initial response occurred was decreased after exposure to
acetylcholine but not bradykinin. _Speculation_: The ductus arteriosus of the fetal lamb constricts when exposed to oxygen. The initial level of P O 2 at which this constriction occurs
decreases, and the maximal degree of constriction increases, with advancing gestational age. The poor response to oxygen of the ductus arteriosus in the immature fetus may be the mechanism
responsible for the high incidence of patent ductus arteriosus in premature infants. Constriction following-oxygen may be augmented by the exposure to acetylcholine or bradykinin. SIMILAR
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DECISION-MAKING AND FUTURE TRIALS Article 22 July 2021 ARTICLE PDF AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Departments of Pediatrics and Pharmacology and the Cardiovascular Research
Institute, University of California, San Francisco, California, USA Dorothy M Mcmurphy, Michael A Heymann, Abraham M Rudolph & Kenneth L Melmon Authors * Dorothy M Mcmurphy View author
publications You can also search for this author inPubMed Google Scholar * Michael A Heymann View author publications You can also search for this author inPubMed Google Scholar * Abraham M
Rudolph View author publications You can also search for this author inPubMed Google Scholar * Kenneth L Melmon View author publications You can also search for this author inPubMed Google
Scholar RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Mcmurphy, D., Heymann, M., Rudolph, A. _et al._ Developmental Changes in Constriction of the
Ductus Arteriosus: Responses to Oxygen and Vasoactive Agents in the Isolated Ductus Arteriosus of the Fetal Lamb. _Pediatr Res_ 6, 231–238 (1972).
https://doi.org/10.1203/00006450-197204000-00004 Download citation * Issue Date: 01 April 1972 * DOI: https://doi.org/10.1203/00006450-197204000-00004 SHARE THIS ARTICLE Anyone you share the
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Nature SharedIt content-sharing initiative KEYWORDS * Acetylcholine * bradykinin * developmental physiology * ductus arteriosus * prematurity