Meeting Abstract
P3.5 Tuesday, Jan. 6 Hemodynamics of embryonic Alligators EME, J*; CROSSLEY II, DA; HICKS, JW; U Cal Irvine; U N. Dakota; U Cal Irvine jeme@uci.edu
Embryonic reptiles and birds as well as fetal mammals have cardiac morphologies that allow mixing of oxygenated and deoxygenated blood (cardiac shunts). This anatomical arrangement is common in developing vertebrates, but the significance of cardiac shunts in embryonic reptiles is unclear. Given hypoxic nest conditions of embryonic reptiles, impacts of cardiac mixing on physiological function must be delineated. However, measurements of in ovo reptilian chorioallantoic membrane (CAM) and great vessel blood flow have not been performed. Using Transonic flow probes, we measured systemic cardiac output and major CAM artery blood flow of normoxic and hypoxic-incubated (10% O2) American alligator embryos at ~90% of incubation. In addition, we measured normoxic CAM venous and arterial blood gas properties. Chronic flow (2h-11d) in the major CAM artery for hypoxic-incubated embryos (92+26ml/min/kg,N=6) was elevated compared to normoxic-incubated embryos (29+14ml/min/kg,N=6;t-test P=0.03). For anesthetized hypoxic-incubated embryos, acute measurements of left aorta (LAo) flow (50+24ml/min/kg,N=5) was equal to combined flow of right aorta, common carotid and subclavian systemic vessels (44+21ml/min/kg,N=5). Similarly, for normoxic-incubated embryos, LAo-flow (27+7ml/min/kg,N=5) did not differ from the other 3 vessels (18+5 ml/min/kg,N=5). CAM venous PO2 (47+6mmHg,N=5) was greater than CAM arterial PO2 (17+3mmHg,N=5;t-test P<0.01), venous PCO2 was lower than arterial (25+4mmHg and 37+7mmHg,respectively;P=0.03) and venous pH was higher (7.45+0.08 and 7.32+0.07;P=0.04). A significant portion of systemic output flows through the LAo in embryonic alligators. In addition, alligator embryos increased CAM flow during chronic hypoxic conditions, and this flow may be mediated by increased output to the systemic circulation, in part via the LAo. NSF IOB 0445680 to JWH
