Meeting Abstract

P3.50  Sunday, Jan. 6  New experimental model to investigate effects of augmented intracardiac shunt COOK, E.Y.*; OWERKOWICZ, T; California State Univ., San Bernardino; California State Univ., San Bernardino cooke300@coyote.csusb.edu

Central vascular shunting is present in all vertebrates during development and lost only in mammals and birds after birth/hatching. The persistence of cardiac shunting among extant reptiles has been queried numerous times, and its adaptive function cast in doubt. Recently, independent studies of experimental elimination of the pulmonary bypass shunt in crocodilians have yielded conflicting results. In contrast to previous approaches, we developed a new squamate model with an augmented intracardiac shunt. The derived cardiac morphology of varanid lizards maintains pressure separation between the pulmonary and systemic circuits and allows only for a small washout shunt from the cavum venosum into the left aorta (LAo). We hypothesised that surgical ligation of the LAo will promote admixture of deoxygenated and oxygenated bloodstreams and effectively augment the intracardiac shunt. We confirmed this by measurement of blood oxygen tension (pO₂) with in-dwelling micro-optodes positioned in the right aorta (RAo) and pulmonary artery (PA) in anaesthetized juvenile savannah monitors (Varanus exanthematicus). Following LAo ligation, we observed an increased pO₂ in the PA and a decreased pO₂ in the RAo, indicating a greater shunt magnitude. We suggest this animal model will facilitate the investigation of increased shunt fraction on overall oxygen transport, tissue growth and oxidative stress. Ultimately, it may help to elucidate whether central vascular shunts serve an adaptive function which might explain their prevalence in reptiles.