Chronic developmental<i>in ovo</i>hypoxic exposure alters femoral Artery and Vein Contractility in Juvenile Alligators (<i>Alligator mississippiensis</i>)

The oxygen level experienced during development is an important factor dictating the phenotype of juvenile and adult animals via developmental phenotypic plasticity. Thus, low oxygen (hypoxia) if experienced during a critical window of development can lead to physiological changes that persist into adulthood. Prior studies of American alligators Alligator mississippiensis have demonstrated that the cardiovascular phenotype exhibits plasticity in response to developmental hypoxia and these phenotypic changes persist into juvenile life. However, the majority of studies have focused on the effects of developmental hypoxia on the heart of these animals, and little is known about the phenotypic responses of the vasculature of the animals. Therefore, we designed a series of studies to investigate the contractility of the femoral artery and vein in response to pharmacological manipulation to understand how chronic hypoxic incubation alters vascular function in juveniles. Alligator mississippiensis eggs were collected from nests and incubated at 30°C and 21% O 2 . At approximately 20% of incubation, eggs were randomly assigned to either normoxia (21% O 2 ) or hypoxia (10% O 2 ) for the remainder of in ovo development. After hatching, animals were raised in normoxic conditions for 4 to 6 years. We examined femoral artery and vein in vitro contractility responses to pharmacological manipulations using wire myography. Regardless of O 2 -incubation conditions, veins exhibited significantly stronger contractions to stepwise increases in KCl levels than did arteries. Neither arteries nor veins responded to the alpha-adrenergic stimulant phenylephrine (PE). In response to angiotensin II (Ang II) contractile response of the veins to was significantly blunted by O 2 incubation levels, with hypoxic animals producing significantly less tension in response to Ang II when compared with veins from normoxic animals. Normoxic arteries and veins generated higher tensions in response to the thromboxane A mimic U 46619 when compared to hypoxic incubated animals. Veins had a significantly stronger relaxation response to sodium nitroprusside when compared to arteries, regardless of oxygen incubation levels. Our findings suggest chronic developmental hypoxic incubation alters femoral artery and vein contractile phenotypes in juvenile alligators, which may be linked to decreased heart rate and lower mean arterial blood pressure seen in previous studies. Funding for the project was provided to D.A.C. II by the National Science Foundation OS 1755187. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.