Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland.
J Comp Physiol B. 2021 Jan;191(1):43-53. doi: 10.1007/s00360-020-01313-1. Epub 2020 Sep 26.
At high temperatures, ventricular beating rate collapses and depresses cardiac output in fish. The role of sarco(endo)plasmic reticulum Ca-ATPase (SERCA) in thermal tolerance of ventricular function was examined in brown trout (Salmo trutta) by measuring heart SERCA and comparing it to that of the dorsolateral myotomal muscle. Activity of SERCA was measured from crude homogenates of cold-acclimated (+ 3 °C, c.a.) and warm-acclimated (+ 13 °C, w.a.) brown trout as cyclopiazonic acid (20 µM) sensitive Ca-ATPase between + 3 and + 33 °C. Activity of the heart SERCA was significantly higher in c.a. than w.a. trout and increased strongly between + 3 and + 23 °C with linear Arrhenius plots but started to plateau between + 23 and + 33 °C in both acclimation groups. The rate of thermal inactivation of the heart SERCA at + 35 °C was similar in c.a. and w.a. fish. Activity of the muscle SERCA was less temperature dependent and more heat resistant than that of the heart SERCA and showed linear Arrhenius plots between + 3 and + 33 °C in both c.a. and w.a. fish. SERCA activity of the c.a. muscle was slightly higher than that of w.a. muscle. The rate of thermal inactivation at + 40 °C was similar for both c.a. and w.a. muscle SERCA at + 40 °C. Although the heart SERCA is more sensitive to high temperatures than the muscle SERCA, it is unlikely to be a limiting factor for heart rate, because its heat tolerance, unlike that of the ventricular beating rate, was not changed by temperature acclimation.
在高温下，心室跳动频率会崩溃并降低鱼类的心脏输出量。本研究通过测量心脏 SERCA 并将其与背外侧肌的 SERCA 进行比较，来研究肌浆网 Ca2+-ATP 酶（SERCA）在褐鳟心室功能耐热性中的作用。从冷适应（+3°C，c.a.）和热适应（+13°C，w.a.）的褐鳟粗匀浆中测量 SERCA 的活性，用环匹阿尼酸（20µM）敏感的 Ca-ATP 酶在+3 到+33°C 之间进行测量。心脏 SERCA 的活性在 c.a. 鳟鱼中显著高于 w.a. 鳟鱼，在+3 到+23°C 之间呈线性 Arrhenius 图谱增加，但在两个适应组中，从+23 到+33°C 开始趋于平稳。在+35°C 时，心脏 SERCA 的热失活速率在 c.a. 和 w.a. 鱼中相似。肌肉 SERCA 的活性比心脏 SERCA 的活性更依赖温度且更耐热，在 c.a. 和 w.a. 鱼中，在+3 到+33°C 之间呈线性 Arrhenius 图谱。c.a. 肌肉的 SERCA 活性略高于 w.a. 肌肉的活性。在+40°C 时，c.a. 和 w.a. 肌肉的 SERCA 的热失活速率相似。尽管心脏 SERCA 对高温比肌肉 SERCA 更敏感，但它不太可能成为心率的限制因素，因为与心室跳动率不同，其耐热性没有因温度适应而改变。
