Meeting Abstract

P1.65  Jan. 4  Effects of differing oxygen incubation levels on the physiology of ductus arteriosi in near-term chicken embryos COPELAND, J.M.*; DZIALOWSKI, E.M.; University of North Texas, Denton JenniferM_Copeland@yahoo.com

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 and chorioallantois. 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 incubation oxygen levels on the vascular reactivity of the DA to catecholamines and oxygen. Chicken embryos were incubated under hypoxic (15% O₂), normoxic (21% O₂) or hyperoxic (30% O₂) conditions. The LDA and RDA in day 18 and internally pipped (IP) embryos were removed, mounted in myograph chambers, and their contractile response was measured under stepwise increases in phenylephrine (PE) and norepinephrine (NE). The contractile response of the LDA and RDA to oxygen was measured as the oxygen level of the organ bath increased from 5% to 30%. In prepipped and IP embryos, maximal contractile responses were observed at 10^-4 M PE and 10^-5 M NE for all treatments. The LDA and RDA responded in similar fashion to both drugs. The contractile response to both PE and NE were significantly lower in embryos incubated under hypoxic conditions than either the controls or hyperoxic embryos. In response to oxygen, there was a developmental increase in the contractile response. The DA from IP hyperoxic embryos had significantly higher contractile response than vessels from the control or hypoxic IP embryos. The oxygen environment in which the embryo was incubating most likely influenced circulating catecholamine levels resulting in differential expression of adrenergic receptors and the response to oxygen. This research was supported by an NSF grant (IOB0417205) awarded to EMD.