Enok Sanne, Leite Gabriella S P C, Leite Cléo A C, Gesser Hans, Hedrick Michael S, Wang Tobias
Zoophysiology, Department of Bioscience, Aarhus University, Aarhus 8000, Denmark
Department of Physiological Sciences, Federal University of São Carlos, São Paulo 13565-905, Brazil.
J Exp Biol. 2016 Oct 1;219(Pt 19):3009-3018. doi: 10.1242/jeb.142729. Epub 2016 Jul 21.
To accommodate the pronounced metabolic response to digestion, pythons increase heart rate and elevate stroke volume, where the latter has been ascribed to a massive and fast cardiac hypertrophy. However, numerous recent studies show that heart mass rarely increases, even upon ingestion of large meals, and we therefore explored the possibility that a rise in mean circulatory filling pressure (MCFP) serves to elevate venous pressure and cardiac filling during digestion. To this end, we measured blood flows and pressures in anaesthetized Python regius The anaesthetized snakes exhibited the archetypal tachycardia as well as a rise in both venous pressure and MCFP that fully account for the approximate doubling of stroke volume. There was no rise in blood volume and the elevated MCFP must therefore stem from increased vascular tone, possibly by means of increased sympathetic tone on the veins. Furthermore, although both venous pressure and MCFP increased during volume loading, there was no evidence that postprandial hearts were endowed with an additional capacity to elevate stroke volume. In vitro measurements of force development of paced ventricular strips also failed to reveal signs of increased contractility, but the postprandial hearts had higher activities of cytochrome oxidase and pyruvate kinase, which probably serves to sustain the rise in cardiac work during digestion.
为了适应消化过程中显著的代谢反应，蟒蛇会增加心率并提高每搏输出量，后者被认为是由于心脏大量快速肥大所致。然而，最近的大量研究表明，即使摄入大量食物，心脏质量也很少增加，因此我们探讨了平均循环充盈压（MCFP）升高有助于在消化过程中提高静脉压和心脏充盈的可能性。为此，我们测量了麻醉的球蟒的血流和压力。麻醉的蛇表现出典型的心动过速，同时静脉压和MCFP升高，这完全解释了每搏输出量大约翻倍的原因。血容量没有增加，因此升高的MCFP必定源于血管张力增加，可能是通过增加静脉上的交感神经张力实现的。此外，尽管在容量负荷期间静脉压和MCFP都增加了，但没有证据表明餐后心脏具有额外提高每搏输出量的能力。对起搏心室条带力量发展的体外测量也未能揭示收缩力增加的迹象，但餐后心脏的细胞色素氧化酶和丙酮酸激酶活性较高，这可能有助于维持消化过程中心脏工作的增加。
