Cox Georgina K, Brill Richard W, Bonaro Kaitlin A, Farrell Anthony P
Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
National Marine Fisheries Service, Northeast Fisheries Science Center, James J. Howard Marine Sciences Laboratory, Highlands, NJ, USA.
J Comp Physiol B. 2017 Feb;187(2):315-327. doi: 10.1007/s00360-016-1033-x. Epub 2016 Sep 27.
The coronary circulation first appeared in the chordate lineage in cartilaginous fishes where, as in birds and mammals but unlike most teleost fishes, it supplies arterial blood to the entire myocardium. Despite the pivotal position of elasmobranch fishes in the evolution of the coronary circulation, the determinants of coronary blood flow have never been investigated in this group. Elasmobranch fishes are of special interest because of the morphological arrangement of their cardiomyocytes. Unlike teleosts, the majority of the ventricular myocardium in elasmobranch fishes is distant to the venous blood returning to the heart (i.e., the luminal blood). Also, the majority of the myocardium is in close association with the coronary circulation. To determine the relative contribution of the coronary and luminal blood supplies to cardiovascular function in sandbar sharks, Carcharhinus plumbeus, we measured coronary blood flow while manipulating cardiovascular status using acetylcholine and adrenaline. By exploring inter- and intra-individual variation in cardiovascular variables, we show that coronary blood flow is directly related to heart rate (R = 0.6; P < 0.001), as it is in mammalian hearts. Since coronary blood flow is inversely related to coronary resistance both in vivo and in vitro, we suggest that in elasmobranch fishes, changes in heart rate mediate changes in coronary vascular resistance, which adjust coronary blood flow appropriately.
冠状动脉循环最早出现在软骨鱼类的脊索动物谱系中，在那里，与鸟类和哺乳动物一样，但与大多数硬骨鱼类不同，它向整个心肌供应动脉血。尽管板鳃鱼类在冠状动脉循环的进化中处于关键地位，但该类群中冠状动脉血流的决定因素从未被研究过。板鳃鱼类因其心肌细胞的形态排列而特别受关注。与硬骨鱼类不同，板鳃鱼类心室心肌的大部分远离返回心脏的静脉血（即管腔内血液）。此外，大部分心肌与冠状动脉循环密切相关。为了确定冠状动脉和管腔血液供应对沙虎鲨（Carcharhinus plumbeus）心血管功能的相对贡献，我们在使用乙酰胆碱和肾上腺素操纵心血管状态的同时测量了冠状动脉血流。通过探索心血管变量的个体间和个体内差异，我们发现冠状动脉血流与心率直接相关（R = 0.6；P < 0.001），就像在哺乳动物心脏中一样。由于在体内和体外冠状动脉血流都与冠状动脉阻力呈负相关，我们认为在板鳃鱼类中，心率的变化介导冠状动脉血管阻力的变化，从而适当地调节冠状动脉血流。
