Abstract
Extract: Response of the ductus arteriosus and umbilical artery to changes in oxygen tension, to acetylcholine, and to sympathetic and parasympathetic blocking agents was studied in vitro in isolated rings obtained from 22 fetal lambs of 98- to 147-day gestation.
After stabilization of tension at a baseline level (0.3–0.7 g) in a environment of 35–45 mm Hg, both increase of the to 550 mm Hg and decrease of the to 8 mm Hg of the bathing solution produced constriction. The mean maximal tension developed by the ductus arteriosus.was 3.91 g at high and 3.87 g at low . The increase in maximal tension developed with advancing gestation was also similar at both high and low .
At levels of 8–550 mm Hg, acetylcholine produced a further increase in tension, whereas bradykinin only produced an increase in tension at high . Alpha and beta sympathetic blockade had no effect on the constrictor response to oxygen. Atropine relaxed the ductus arteriosus and umbilical artery at both high and low levels; the degree of relaxation was related to drug concentration. Acetylcholin-esterase also relaxed the ductus arteriosus constricted by oxygen. The cholinesterase inhibitor, edrophonium, produced ductus constriction at of 35–45 mm Hg with little further effect from high . The constrictor effect of high or low on the ductus arteriosus and umbilical artery seems to be mediated through release of acetylcholine.
Speculation: Postnatal closure of the ductus arteriosus is effected by an increase in oxygen environment. This is probably mediated by the release of acetylcholine. Inability of many premature infants to close effectively the ductus arteriosus is therefore probably due to an inability to synthesize or release adequate amounts of acetylcholine rather than to lack of the mechanism of muscular constriction.
Parasympathetic blocking agents may be of use in preventing constriction of the ductus arteriosus in infants with congenital heart disease who are dependent on its patency for survival.
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Oberhänsli-weiss, I., Heymann, M., Rudolph, A. et al. The Pattern and Mechanisms of Response to Oxygen by the Ductus Arteriosus and Umbilical Artery. Pediatr Res 6, 693–700 (1972). https://doi.org/10.1203/00006450-197209000-00001
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DOI: https://doi.org/10.1203/00006450-197209000-00001
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