Deitch E J, Fletcher G L, Petersen L H, Costa I A S F, Shears M A, Driedzic W R, Gamperl A K
Ocean Sciences Centre, Memorial University of Newfoundland, St John's, Newfoundland A1C 5S7, Canada.
J Exp Biol. 2006 Apr;209(Pt 7):1310-25. doi: 10.1242/jeb.02105.
In recent years, there has been a great deal of interest in how growth hormone (GH) transgenesis affects fish physiology. However, the results of these studies are often difficult to interpret because the transgenic and non-transgenic fish had very different environmental/rearing histories. This study used a stable line of size-matched GH Atlantic salmon (Salmo salar) that were reared in a shared tank with controls (at 10 degrees C, for approximately 9 months) to perform a comprehensive examination of the cardiorespiratory physiology of GH transgenic salmon, and serves as a novel test of the theory of symmorphosis. The GH transgenic salmon had a 3.6x faster growth rate, and 21 and 25% higher values for mass-specific routine and standard oxygen consumption (M(O(2))), respectively. However, there was no concurrent increase in their maximum M(O(2)), which resulted in them having an 18% lower metabolic scope and a 9% reduction in critical swimming speed. This decreased metabolic capacity/performance was surprising given that the transgenics had a 29% larger heart with an 18% greater mass-specific maximum in situ cardiac output, a 14% greater post-stress blood haemoglobin concentration, 5-10% higher red muscle and heart aerobic enzyme (citrate synthase or cytochrome oxidase) activities, and twofold higher resting and 1.7x higher post-stress, catecholamine levels. However, gill surface area was the only cardiorespiratory parameter that was not enhanced, and our data suggest that gill oxygen transfer may have been limiting. Overall, this research: (1) shows that there are significant metabolic costs associated with GH transgenesis in this line of Atlantic salmon; (2) provides the first direct evidence that cardiac function is enhanced by GH transgenesis; (3) shows that a universal upregulation of post-smolt (adult) GH transgenic salmon cardiorespiratory physiology, as suggested by symmorphosis, does not occur; and (4) supports the idea that whereas differences in arterial oxygen transport (i.e. cardiac output and blood oxygen carrying capacity) are important determinants of inter-specific differences in aerobicity, diffusion-limited processes must be enhanced to achieve substantial intra-specific improvements in metabolic and swimming performance.
近年来，生长激素（GH）转基因如何影响鱼类生理受到了广泛关注。然而，这些研究结果往往难以解释，因为转基因鱼和非转基因鱼的环境/饲养历史差异很大。本研究使用了一组大小匹配的稳定品系GH大西洋鲑（Salmo salar），它们与对照组在同一个水箱中饲养（10摄氏度，约9个月），以全面检查GH转基因鲑鱼的心肺生理，并作为对协同适应理论的一种新测试。GH转基因鲑鱼的生长速度快3.6倍，质量特异性常规耗氧量和标准耗氧量（M（O₂））分别高出21%和25%。然而，它们的最大M（O₂）并没有同时增加，这导致它们的代谢范围降低了18%，临界游泳速度降低了9%。考虑到转基因鱼的心脏大29%，质量特异性最大原位心输出量高18%，应激后血红蛋白浓度高14%，红色肌肉和心脏有氧酶（柠檬酸合酶或细胞色素氧化酶）活性高5 - 10%，静息时儿茶酚胺水平高两倍，应激后高1.7倍，这种代谢能力/性能的下降令人惊讶。然而，鳃表面积是唯一没有增强的心肺参数，我们的数据表明鳃的氧气转移可能受到了限制。总体而言，本研究：（1）表明在这一品系的大西洋鲑中，GH转基因存在显著的代谢成本；（2）提供了首个直接证据，证明GH转基因可增强心脏功能；（3）表明如协同适应理论所暗示的，幼鲑后（成体）GH转基因鲑鱼心肺生理的普遍上调并未发生；（4）支持了这样一种观点，即虽然动脉氧运输的差异（即心输出量和血液携氧能力）是种间有氧能力差异的重要决定因素，但必须增强扩散受限过程，才能在种内实现代谢和游泳性能的显著改善。
