Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark
Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark.
J Exp Biol. 2018 Aug 23;221(Pt 16):jeb177766. doi: 10.1242/jeb.177766.
In animals with functional division of blood systemic and pulmonary pressures, such as mammals, birds, crocodilians and a few non-crocodilian reptiles, the vessel walls of systemic and pulmonary arteries are exquisitely adapted to endure different pressures during the cardiac cycle, systemic arteries being stronger and stiffer than pulmonary arteries. However, the typical non-crocodilian reptile heart possesses an undivided ventricle that provides similar systolic blood pressure to both circuits. This raises the question whether in these species the systemic and pulmonary mechanical vascular properties are similar. Snakes also display large organ plasticity and increased cardiac output in response to digestion, and we speculate how the vascular circuit would respond to this further stress. We addressed these questions by testing the mechanical vascular properties of the dorsal aorta and the right pulmonary artery of fasted and fed yellow anacondas, , a snake without functional ventricular separation that also exhibits large metabolic and cardiovascular responses to digestion. Similar to previous studies, the dorsal aorta was thicker, stronger, stiffer and more elastic than the pulmonary artery. However, unlike any other species studied so far, the vascular distensibility (i.e. the relative volume change given a pressure change) was similar for the two circuits. Most striking, the pulmonary artery elasticity (i.e. its capacity to resume its original form after being stretched) and distensibility increased during digestion, which suggests that this circuit is remodeled to accommodate the larger stroke volume and enhance the Windkessel effect, thus providing a more constant blood perfusion during digestion.
在具有血液系统和肺循环功能分离的动物中,如哺乳动物、鸟类、鳄鱼和少数非鳄类爬行动物,体循环和肺循环的血管壁对外界压力的变化具有高度适应性,体循环的血管壁比肺循环的血管壁更强壮、更坚韧。然而,典型的非鳄类爬行动物的心脏没有分隔心室,为体循环和肺循环提供相似的收缩压。这就提出了一个问题,即在这些物种中,体循环和肺循环的力学血管特性是否相似。蛇类在消化过程中也表现出较大的器官可塑性和心输出量增加,我们推测血管循环将如何应对这种进一步的压力。我们通过测试饥饿和进食的黄色水蚺的背主动脉和右肺动脉的力学血管特性来回答这些问题,黄色水蚺是一种没有功能性心室分隔的蛇,它也表现出对消化的巨大代谢和心血管反应。与之前的研究相似,背主动脉比肺动脉更厚、更强壮、更坚硬和更有弹性。然而,与迄今为止研究的任何其他物种不同,两个循环的血管可扩张性(即给定压力变化时的相对体积变化)相似。最引人注目的是,肺动脉的弹性(即其在被拉伸后恢复原来形状的能力)和可扩张性在消化过程中增加,这表明该循环被重塑以适应更大的每搏输出量,并增强了缓冲器效应,从而在消化过程中提供更稳定的血液灌注。