Cardiac shunting does not constrain aerobic capacity of the American alligator
Cardiac shunting does not constrain aerobic capacity of the American alligator
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心脏分流不会限制美洲鳄的有氧能力
DOI：
10.1096/fasebj.24.1_supplement.988.5
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
J. Hicks
中科院分区：
文献类型：
--
作者：
T. Owerkowicz;J. Eme;June Gwalthney;J. Blank;J. Hicks
尽管鳄鱼和鸟类的心脏相似，但它们的有氧能力有很大的不同。我们调查了这是否由于流出道设计的差异，这允许鳄鱼心脏分流，而不是鸟类。我们假设心脏分流的移除将通过迫使整个右室射血容量到肺来提高有氧能力(VO2max)。我们通过手术阻断了鳄鱼孵化后的左主动脉，使其无法分流。经过17个月的生长和运动训练，我们对扬子鳄进行了分级跑步机运动测试，并测量了它们的最大摄氧量。我们发现手术改变的鳄鱼的VO2max(7.7mlO2/kg/min)与假手术的(8.0mlO2/kg/min)没有显著差异。为了进一步测试运动期间是否发生心脏分流，我们测量了左和右主动脉的血流量。分流(左主动脉的净前向血流)在未受干扰的动物中在静息时发生，在强迫运动开始时消失，在未受干扰的恢复期间缓慢恢复。这表明心脏分流能力不会限制鳄鱼的有氧运动能力，因为在运动时分流是关闭的。我们认为，非鸟类兽脚亚目动物可能继续享受心脏分流的好处，即使他们进化出更优越的有氧能力。由国家科学基金会IOB 04445680向仲量联行提供资金。
Despite having a similar four‐chambered heart, crocodilians and birds differ widely in their aerobic capacity. We investigated whether this is due to differences in outflow tract design, which allows for cardiac shunting in crocodilians, but not in birds. We hypothesized that removal of cardiac shunt will improve aerobic capacity (VO2max) by forcing the entire right ventricular ejection volume to the lungs. We surgically occluded the left aorta in alligator hatchlings to render them incapable of shunting. After 17 months of growth and exercise training, we subjected alligators to a graded treadmill exercise test and measured their VO2max. We found no significant difference in VO2max between surgically‐altered (7.7 mlO2/kg/min) and sham‐operated (8.0 mlO2/kg/min) alligators. To further test whether cardiac shunting occurs during exercise, we measured blood flow in the left and right aortae. Shunting (net forward flow in the left aorta) occurred at rest in undisturbed animals, disappeared at the onset of forced exercise, and returned slowly during undisturbed recovery. This suggests cardiac shunting ability does not limit aerobic performance in crocodilians, because the shunt is turned off during exercise. We propose that non‐avian theropods may have continued to enjoy benefits of cardiac shunting, even as they evolved a more superior aerobic capacity. Funded by NSF IOB 04445680 to JWH.