Contractile response of avian ductus arteriosus to chronic elevated oxygen levels

Abstract

The ductus arteriosus (DA) is an oxygen sensitive embryonic blood vessel present in all developing amniotes. The DA connects the pulmonary artery to the aorta and shunts blood away from nonfunctioning lungs and towards the fetal respiratory organ. In birds at hatching, a rise in arterial PO2 initiates DA smooth muscle cell constriction to initiate closure. As the avian embryo approaches hatching, the DA contraction becomes more sensitive to oxygen. In this study we asked how 3‐hr chronic exposure to elevated oxygen levels of 5, 25, or 73 kPa oxygen influenced the oxygen stimulated contraction of the late term chicken DA. During the 3‐hr exposure, the greatest increase in contraction was seen in response to 73 kPa oxygen with smaller change occurring at 5 kPa oxygen exposure. Exposure to all three levels of oxygen resulted in resetting the baseline tension when oxygen was returned to 2.5 kPa. These changes in response to chronic elevated oxygen disappeared in the presence of cytochalasin B. These findings suggest that DA exposure to chronic elevated oxygen results in cellular changes in the contractile properties of the vessel allowing it to respond with greater contractile strength in response to a rise in oxygen.