Oxygen-induced vasoconstriction is an initial trigger for ductus arteriosus (DA) closure. The aim of this study was to investigate the role of reactive oxygen species (ROS) in the developmental responses to oxygen in chicken DA. Experiments were performed in the pulmonary and the aortic sides of the DA isolated from embryos incubated for 15 or 20 days. ROS generation in DA was assessed using the fluorescent dye 2,7-dichlorofluorescein (DCF).

In 20-day embryos, the increase in oxygen tension from 0 to 21% caused a contraction in rings obtained from the pulmonary side while a relaxant response was elicited in those obtained from the aortic side. In contrast, no changes were found following 21% oxygen exposure in either the pulmonary or the aortic sides of the 15-day DA. The contraction to oxygen was markedly prevented by the NADPH oxidase inhibitor apocynin, the mitochondrial electron transport chain inhibitor rotenone and by polyethylenglycol-catalase. In addition, 21% oxygen caused an increase in ROS production in the pulmonary end 20-day DA, but not in the other preparations. Finally, addition of t-butyl-hydroperoxide mimicked the responses induced by 21% oxygen (no effect in 15-day and contraction and relaxation in pulmonary and aortic sides of the 20-day DA, respectively). Our results are in favor of ROS (especially H₂O₂) as mediators of the contractile responses to oxygen in the chicken DA.