Pottinger T G, Balm P H, Pickering A D
Institute of Freshwater Ecology, Windermere Laboratory, Far Sawrey, Ambleside, United Kingdom.
Gen Comp Endocrinol. 1995 Jun;98(3):311-20. doi: 10.1006/gcen.1995.1073.
A significant reduction in stress-induced plasma cortisol levels is apparent in mature male rainbow trout compared to immature fish of both sexes and of the same age and strain. Mean plasma cortisol levels in groups of immature fish subjected to a standard 1-hr confinement stress were consistently higher (range 93.9 +/- 4.9-114.8 +/- 4.1 ng ml-1) than mean levels in mature males exposed to the same procedure (range 47.0 +/- 4.3-71.7 +/- 5.7 ng ml-1), throughout the 4-month period around spawning (P < 0.001). Body weight was not found to be a significant determinant of poststress cortisol level. The dissimilarity in plasma cortisol levels between mature and immature fish following confinement does not stem from differences in the dynamics of the response; during a 24-hr period of confinement the rate of elevation of plasma cortisol levels was similar for both mature male and immature fish, but mature male fish attained a significantly lower peak cortisol level (51.6 +/- 5.2 ng ml-1) than immature fish (89.5 +/- 7.7 ng ml-1), a disparity which was maintained throughout the period of stress (P < 0.05-P < 0.001). The reduced responsiveness of the interrenal tissue of mature male fish during stress appears to be modulated by the hypothalamus/pituitary. Plasma ACTH levels in mature male trout (44 +/- 9 pg ml-1) are significantly lower than those in immature fish (71 +/- 9 pg ml-1, P < 0.01) within 30 min of the onset of confinement and remain so during a 3-hr period of confinement. These data suggest that the cortisol/ACTH feedback equilibrium has been modified in mature fish to a lower "set point." Furthermore, although stress caused a significant decline of plasma alpha-MSH levels in both immature fish and mature males, N-acetyl-beta-endorphin levels were reduced only in mature male fish during confinement stress.
与同龄同品系的未成熟雌雄虹鳟鱼相比，成熟雄性虹鳟鱼应激诱导的血浆皮质醇水平显著降低。在产卵前后的4个月期间，接受标准1小时限制应激的未成熟鱼组的平均血浆皮质醇水平（范围93.9±4.9 - 114.8±4.1 ng/ml）始终高于接受相同程序的成熟雄性虹鳟鱼的平均水平（范围47.0±4.3 - 71.7±5.7 ng/ml）（P<0.001）。未发现体重是应激后皮质醇水平的重要决定因素。限制后成熟鱼和未成熟鱼血浆皮质醇水平的差异并非源于反应动态的不同；在24小时的限制期间，成熟雄性虹鳟鱼和未成熟鱼血浆皮质醇水平的升高速率相似，但成熟雄性虹鳟鱼达到的皮质醇峰值水平（51.6±5.2 ng/ml）显著低于未成熟鱼（89.5±7.7 ng/ml），这种差异在整个应激期间持续存在（P<0.05 - P<0.001）。成熟雄性虹鳟鱼在应激期间肾间组织反应性降低似乎受下丘脑/垂体调节。在限制开始后30分钟内，成熟雄性虹鳟鱼的血浆促肾上腺皮质激素（ACTH）水平（44±9 pg/ml）显著低于未成熟鱼（71±9 pg/ml，P<0.01），并在3小时的限制期间一直保持较低水平。这些数据表明，成熟鱼中皮质醇/ACTH反馈平衡已调整到较低的“设定点”。此外，尽管应激导致未成熟鱼和成熟雄性虹鳟鱼的血浆α-促黑素细胞激素（α-MSH）水平均显著下降，但在限制应激期间，只有成熟雄性虹鳟鱼的N-乙酰-β-内啡肽水平降低。
