Blank Jason M, Morrissette Jeffery M, Davie Peter S, Block Barbara A
Tuna Research and Conservation Center, Stanford University, Hopkins Marine Station, Oceanview Boulevard, Pacific Grove, CA 93950, USA.
J Exp Biol. 2002 Jul;205(Pt 13):1881-8. doi: 10.1242/jeb.205.13.1881.
Tuna are endothermic fish with high metabolic rates, cardiac outputs and aerobic capacities. While tuna warm their skeletal muscle, viscera, brain and eyes, their hearts remain near ambient temperature, raising the possibility that cardiac performance may limit their thermal niches. We used an in situ perfused heart preparation to investigate the effects of acute temperature change and the effects of epinephrine and extracellular Ca(2+) on cardiac function in yellowfin tuna (Thunnus albacares). Heart rate showed a strong temperature-dependence, ranging from 20 beats min(-1) at 10 degrees C to 109 beats min(-1) at 25 degrees C. Maximal stroke volume showed an inverse temperature-dependence, ranging from 1.4 ml kg(-1) at 15 degrees C to 0.9 ml kg(-1) at 25 degrees C. Maximal cardiac outputs were 27 ml kg(-1) min(-1) at 10 degrees C and 98 ml kg(-1) min(-1) at 25 degrees C. There were no significant effects of perfusate epinephrine concentrations between 1 and 100 nmol l(-1) at 20 degrees C. Increasing extracellular Ca(2+) concentration from 1.84 to 7.36 mmol l(-1) at 20 degrees C produced significant increases in maximal stroke volume, cardiac output and myocardial power output. These data demonstrate that changes in heart rate and stroke volume are involved in maintaining cardiac output during temperature changes in tuna and support the hypothesis that cardiac performance may limit the thermal niches of yellowfin tuna.
金枪鱼是具有高代谢率、心输出量和有氧能力的温血鱼类。虽然金枪鱼会使它们的骨骼肌、内脏、大脑和眼睛变暖，但它们的心脏温度仍接近环境温度，这增加了心脏功能可能限制其热生态位的可能性。我们使用原位灌注心脏标本，研究了急性温度变化以及肾上腺素和细胞外Ca(2+)对黄鳍金枪鱼（Thunnus albacares）心脏功能的影响。心率表现出强烈的温度依赖性，范围从10℃时的20次/分钟到25℃时的109次/分钟。最大搏出量表现出与温度相反的依赖性，范围从15℃时的1.4 ml/kg到25℃时的0.9 ml/kg。最大心输出量在10℃时为27 ml/kg·min，在25℃时为98 ml/kg·min。在20℃时，灌注液中肾上腺素浓度在1至100 nmol/L之间没有显著影响。在20℃时，将细胞外Ca(2+)浓度从1.84 mmol/L增加到7.36 mmol/L，会使最大搏出量、心输出量和心肌功率输出显著增加。这些数据表明，心率和搏出量的变化参与了金枪鱼温度变化期间的心输出量维持，并支持心脏功能可能限制黄鳍金枪鱼热生态位的假设。
Zotero 插件