Meeting Abstract
74.1 Monday, Jan. 6 08:00 Cardiovascular regulation in embryonic American alligators during chronic exposure to reduced environmental oxygen. CROSSLEY II , DA*; ELSEY, R; EME, J; Univ of North Texas; Louisiana Depart of Wildlife and Fisheries,; McMaster University dane.crossley@unt.edu
In response to chronic developmental stress, embryonic reptiles exhibit phenotypic plasticity resulting in multiple morphological and physiological modifications. In the majority of these studies, animals have been investigated in a laboratory setting under normoxic conditions (21% O2). Although this experimental paradigm has been useful in the identification of plasticity in cardiovascular development, adjustments in regulation in alligator embryos during chronic exposure to hypoxic conditions are unknown. The goal of this study was to determine how embryonic alligators maintain convective O2 transport in continuous hypoxic conditions during late development. . Embryonic alligators were incubated under normoxic and hypoxic (10% O2) conditions. At 70% and 90% of incubation embryos were instrumented to measure arterial pressure and then continuously exposed to10% oxygen. In continuous hypoxia both normoxia and hypoxia-incubated embryos were relatively bradycardic and hypotensive at 70% and 90% of development. Measurement of cholinergic and adrenergic tone revealed that cholinergic tone on heart rate was absent during chronic hypoxia, but both beta and alpha adrenoceptor tone was present. In addition the hypoxia-incubated embryos exhibited an intensified beta adrenergic tone on heart rate, relative to the normoxic group, when measured in continuous hypoxic conditions while the alpha adrenergic tone on the vasculature was constant. Our findings suggest that during chronic hypoxic conditions embryonic alligator reduce heart rate and blood pressure possibly due to the direct actions of low oxygen. However, this bradycardic and hypotensive phenotype appears to be offset by the presence of beta adrenergic tone on heart rate and alpha adrenergic tone on the vasculature, thus ensuring adequate tissue oxygen delivery.
