Dept. of Cell Biology, University of Calabria, Italy.
Comp Biochem Physiol A Mol Integr Physiol. 2013 Feb;164(2):356-62. doi: 10.1016/j.cbpa.2012.10.037. Epub 2012 Nov 1.
The Frank-Starling law is a fundamental property of the vertebrate myocardium which allows, when the end-diastolic volume increases, that the consequent stretch of the myocardial fibers generates a more forceful contraction. It has been shown that in the eel (Anguilla anguilla) heart, nitric oxide (NO) exerts a direct myocardial relaxant effect, increasing the sensitivity of the Frank-Starling response (Garofalo et al., 2009). With the use of isolated working heart preparations, this study investigated the relationship between NO modulation of Frank-Starling response and temperature challenges in the eel. The results showed that while, in long-term acclimated fish (spring animals perfused at 20 °C and winter animals perfused at 10 °C) the inhibition of NO production by L-N5 (1-iminoethyl)ornithine (L-NIO) significantly reduced the Frank-Starling response, under thermal shock conditions (spring animals perfused at 10 or 15 °C and winter animals perfused at 15 or 20 °C) L-NIO treatment resulted without effect. Western blotting analysis revealed a decrease of peNOS and pAkt expressions in samples subjected to thermal shock. Moreover, an increase in Hsp90 protein levels was observed under heat thermal stress. Together, these data suggest that the NO synthase/NO-dependent modulation of the Frank-Starling mechanism in fish is sensitive to thermal stress.
弗兰克-斯塔林定律是脊椎动物心肌的一个基本特性，当舒张末期容积增加时，心肌纤维的拉伸会产生更有力的收缩。已经表明，在鳗鱼（Anguilla anguilla）心脏中，一氧化氮（NO）发挥直接的心肌松弛作用，增加了弗兰克-斯塔林反应的敏感性（Garofalo 等人，2009 年）。本研究使用分离的工作心脏制剂，研究了 NO 对弗兰克-斯塔林反应的调制与鳗鱼体温挑战之间的关系。结果表明，虽然在长期适应环境的鱼类（春季动物在 20°C 下灌注，冬季动物在 10°C 下灌注）中，L-N5（1-亚氨基乙基）鸟氨酸（L-NIO）抑制 NO 产生显著降低了弗兰克-斯塔林反应，但在热冲击条件下（春季动物在 10°C 或 15°C 下灌注，冬季动物在 15°C 或 20°C 下灌注），L-NIO 处理没有效果。Western blot 分析显示，热冲击样品中 peNOS 和 pAkt 的表达减少。此外，在热应激下观察到 Hsp90 蛋白水平的增加。这些数据表明，鱼类中 NO 合酶/NO 依赖性弗兰克-斯塔林机制的调制对热应激敏感。
