COPELAND, J.M.*; DZIALOWSKI, E.M.; University of North Texas, Denton: Effects of hypoxic incubation on reactivity and morphology of the ductus arteriosi in near-term chicken embryos

The developing avian embryo has a left ductus arteriosus (LDA) and a right ductus arteriosus (RDA) that shunt pulmonary blood away from the lungs and to the systemic circuit. During the transition to lung respiration at hatching, vasoconstriction occurs preferentially at the proximal portion of the ductus arteriosus (DA). In this study, we examined the influence of oxygen levels during incubation on the vascular reactivity and morphology of the LDA and RDA in day 18 and internally pipped chicken embryos. Chicken embryos were incubated under normoxia (21% O₂) or hypoxia (15% O₂). We dissected out the proximal portion of the LDA and the RDA of prepipped and internally pipped embryos and mounted the two portions into myograph chambers. The contractile response of the LDA and RDA were measured under stepwise increases in phenylephrine (PE) and norepinephrine (NE). In prepipped and internally pipped embryos, maximal contractile responses were observed at 10^-4 M PE and 10^-5 M NE. The LDA and RDA responded in similar fashion to both drugs. The contractile response to PE was significantly lower in embryos incubated in hypoxia. A similar significantly lower contractile response to NE was observed in day 18 embryos incubated in hypoxia. However, there were no differences in the response to NE in IP embryos incubated in hypoxia and normoxia. Additionally, embryos exposed to hypoxia had significantly shorter proximal portions of the DA compared with the normoxic incubated embryos. Thus, incubation in hypoxia resulted in significant changes in the physiology and morphology of the DA. This study was funded by NSF operating grant IOB0417205.