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 Po2, environment of 35–45 mm Hg, both increase of the Po2 to 550 mm Hg and decrease of the Po2 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 P0, and 3.87 g at low Po2. The increase in maximal tension developed with advancing gestation was also similar at both high and low Po2.
At Po2, levels of 8–550 mm Hg, acetylcholine produced a further increase in tension, whereas bradykinin only produced an increase in tension at high PO2. 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 Po2 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 P0, of 35–45 mm Hg with little further effect from high Po2. The constrictor effect of high or low Po2 on the ductus arteriosus and umbilical artery seems to be mediated through release of acetylcholine.
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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/10.1203/00006450-197207000-00001
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DOI: https://doi.org/10.1203/00006450-197207000-00001