Department of Biology, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland.
J Comp Physiol B. 2013 May;183(4):467-76. doi: 10.1007/s00360-012-0724-1. Epub 2012 Dec 13.
Cardiac function in fish acclimates to long-term temperature shifts by generating compensatory changes in structure and function of sarcoplasmic reticulum (SR) including the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2). The current study compares temperature responses of the cardiac SERCA in two fish species, burbot (Lota lota) and crucian carp (Carassius carassius), which differ in regard to thermal tolerance and activity pattern. Burbot are cold stenothermal and cold-active, while crucian carp are eurythermal and cold-dormant. The fish were acclimated at 4 °C (cold-acclimation, CA) or 18 °C (warm-acclimation, WA) and expression of SERCA proteins and transcript was measured from atrium and ventricle. Burbot heart expresses one major isoform of SERCA (110 kDa), while crucian carp heart expresses two isoforms (110 and 93 kDa). Expression of SERCA proteins was about four times higher (P < 0.05) in the heart of CA burbot than WA burbot, in both cardiac chambers. In the heart of crucian carp, thermal acclimation did not affect SERCA proteins, in either chamber (P > 0.05). The expression of SERCA transcripts did not follow the expression pattern of SERCA protein in either species, suggesting that SERCA expression is mainly regulated posttranscriptionally. These findings show that the stenothermal and cold-active burbot compensates for the decrease in ambient temperature by increasing the expression of SERCA. In the eurythermal and cold-dormant crucian carp SERCA expression is independent of temperature, while the presence of two SERCA isoforms may provide some thermal independence in SR Ca(2+) pumping.
鱼类的心脏功能通过肌浆网（SR）结构和功能的代偿性变化来适应长期的温度变化，包括肌浆网（endo）浆网膜 Ca(2+)-ATP 酶（SERCA2）。本研究比较了两种鱼类，黑斑狗鱼（Lota lota）和鲫鱼（Carassius carassius）的心脏 SERCA 的温度响应，这两种鱼类在热耐受性和活动模式上存在差异。黑斑狗鱼是冷狭温性和冷活性的，而鲫鱼是广温性和冷休眠的。鱼在 4°C（冷驯化，CA）或 18°C（暖驯化，WA）下驯化，并从心房和心室测量 SERCA 蛋白和转录物的表达。黑斑狗鱼心脏表达一种主要的 SERCA 同工型（110 kDa），而鲫鱼心脏表达两种同工型（110 和 93 kDa）。CA 黑斑狗鱼心脏中的 SERCA 蛋白表达比 WA 黑斑狗鱼高约四倍（P<0.05），在两个心腔中都是如此。在鲫鱼心脏中，热驯化对两个心腔中的 SERCA 蛋白均无影响（P>0.05）。在这两个物种中，SERCA 转录物的表达并不遵循 SERCA 蛋白的表达模式，这表明 SERCA 的表达主要受转录后调控。这些发现表明，冷狭温性和冷活性的黑斑狗鱼通过增加 SERCA 的表达来补偿环境温度的降低。在广温性和冷休眠的鲫鱼中，SERCA 的表达与温度无关，而两种 SERCA 同工型的存在可能为 SR Ca(2+)泵提供一定的热独立性。
