Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487-0344, USA.
J Exp Biol. 2010 Jan 1;213(1):78-88. doi: 10.1242/jeb.034058.
Individually, the metabolic demands of digestion or movement can be fully supported by elevations in cardiovascular performance, but when occurring simultaneously, vascular perfusion may have to be prioritized to either the gut or skeletal muscles. Burmese pythons (Python molurus) experience similar increases in metabolic rate during the digestion of a meal as they do while crawling, hence each would have an equal demand for vascular supply when these two actions are combined. To determine, for the Burmese python, whether blood flow is prioritized when snakes are digesting and moving, we examined changes in cardiac performance and blood flow in response to digestion, movement, and the combination of digestion and movement. We used perivascular blood flow probes to measure blood flow through the left carotid artery, dorsal aorta, superior mesenteric artery and hepatic portal vein, and to calculate cardiac output, heart rate and stroke volume. Fasted pythons while crawling experienced a 2.7- and 3.3-fold increase, respectively, in heart rate and cardiac output, and a 66% decrease in superior mesenteric flow. During the digestion of a rodent meal equaling in mass to 24.7% of the snake's body mass, heart rate and cardiac output increased by 3.3- and 4.4-fold, respectively. Digestion also resulted in respective 11.6- and 14.1-fold increases in superior mesenteric and hepatic portal flow. When crawling while digesting, cardiac output and dorsal aorta flow increased by only 21% and 9%, respectively, a modest increase compared with that when they start to crawl on an empty stomach. Crawling did triggered a significant reduction in blood flow to the digesting gut, decreasing superior mesenteric and hepatic portal flow by 81% and 47%, respectively. When faced with the dual demands of digestion and crawling, Burmese pythons prioritize blood flow, apparently diverting visceral supply to the axial muscles.
个体而言，心血管性能的提高可以完全满足消化或运动的代谢需求，但当这两种需求同时发生时，血管灌注可能需要优先考虑肠道或骨骼肌。缅甸蟒在消化食物时，代谢率会像爬行时一样升高，因此当这两种行为同时发生时，它们对血管供应的需求是相等的。为了确定缅甸蟒在消化和移动时血液流动是否优先，我们检查了心脏性能和血液流动对消化、移动以及消化和移动结合的反应变化。我们使用血管周围血流探头测量通过左颈动脉、背主动脉、肠系膜上动脉和肝门静脉的血流，并计算心输出量、心率和每搏输出量。禁食的蟒蛇在爬行时，心率和心输出量分别增加了 2.7 倍和 3.3 倍，肠系膜上血流量减少了 66%。在消化相当于蛇体重 24.7%的啮齿动物食物时，心率和心输出量分别增加了 3.3 倍和 4.4 倍。消化还导致肠系膜上和肝门静脉流量分别增加了 11.6 倍和 14.1 倍。当消化时爬行时，心输出量和背主动脉流量仅分别增加了 21%和 9%，与空腹开始爬行时相比，这只是适度增加。爬行确实会导致消化肠道的血流显著减少，肠系膜上和肝门静脉流量分别减少 81%和 47%。当面临消化和爬行的双重需求时，缅甸蟒优先考虑血液流动，显然将内脏供应转移到轴向肌肉。
