Sheridan M A
Gen Comp Endocrinol. 1986 Nov;64(2):220-38. doi: 10.1016/0016-6480(86)90007-9.
Juvenile coho salmon, Oncorhynchus kisutch, were either immersed in thyroxin-containing water (T4; 20 micrograms/ml) or implanted with cortisol (5 mg), bovine growth hormone (GH; 1.5 microgram/g body wt), or ovine prolactin (PRL; 1.5 microgram/g body wt), both early and late in smoltification. T4 and cortisol treatment stimulated lipid mobilization in parr. T4-stimulated lipid mobilization was indicated by decreased total lipids, primarily as triacylglycerols, and increased lipolytic enzyme (triacylglycerol lipase) activity in the liver and dark muscle. T4-stimulated lipid mobilization from mesenteric fat was indicated by decreased total tissue mass and by increased lipase activity. Cortisol caused significant reductions in total lipid concentration and triacylglycerol content of the liver and dark muscle; these effects were accompanied by increased lipase activity. Cortisol treatment did not affect mesenteric fat total lipid concentration, total tissue mass, or triacylglycerol content. However, cortisol implantation did enhance mesenteric fat lipase activity. Thyroxin and cortisol treatment failed to elicit alterations in the pattern of tissue lipid mobilization of smolts. GH stimulated lipid mobilization from coho salmon parr. Depletion of liver total lipids was accompanied by increased lipolytic enzyme (triacylglycerol lipase) activity. GH had limited effects on dark muscle and mesenteric fat. In smolts, GH had virtually no effect on lipid mobilization. PRL strongly stimulated lipid mobilization in parr; this effect was evident in all depots studied (liver, dark muscle, mesenteric fat). Decreases in total lipid concentration, or in total tissue mass (mesenteric fat), were accompanied by increased lipase activity and generally resulted in reduced tissue triacylglycerol content. Smolts appeared refractory to PRL treatment. Smolts (characteristically possessing elevated liver lipase activity) that were hypophysectomized exhibited low levels of liver lipase activity. Cortisol replacement restored enzyme activity to approximately the same levels as those observed in sham-operated controls. GH replacement restored lipase activity, but not to the levels observed in sham-operated controls. These results indicate that T4, cortisol, GH, and PRL all stimulate lipid mobilization in developing salmon by enhancement of lipolysis and suggest that T4, cortisol, GH, and PRL are among the factors which contribute to smoltification-associated lipid depletion.
将幼年银大麻哈鱼（Oncorhynchus kisutch）在银化前期和后期分别浸入含甲状腺素的水中（T4；20微克/毫升），或植入皮质醇（5毫克）、牛生长激素（GH；1.5微克/克体重）或绵羊催乳素（PRL；1.5微克/克体重）。T4和皮质醇处理刺激了幼鲑的脂质动员。T4刺激的脂质动员表现为总脂质减少，主要是三酰甘油减少，以及肝脏和暗色肌肉中脂解酶（三酰甘油脂肪酶）活性增加。T4刺激肠系膜脂肪的脂质动员表现为组织总质量减少和脂肪酶活性增加。皮质醇导致肝脏和暗色肌肉的总脂质浓度和三酰甘油含量显著降低；这些效应伴随着脂肪酶活性增加。皮质醇处理不影响肠系膜脂肪的总脂质浓度、总组织质量或三酰甘油含量。然而，植入皮质醇确实增强了肠系膜脂肪的脂肪酶活性。甲状腺素和皮质醇处理未能引起银化幼鱼组织脂质动员模式的改变。GH刺激银大麻哈鱼幼鲑的脂质动员。肝脏总脂质的消耗伴随着脂解酶（三酰甘油脂肪酶）活性增加。GH对暗色肌肉和肠系膜脂肪的影响有限。在银化幼鱼中，GH对脂质动员几乎没有影响。PRL强烈刺激幼鲑的脂质动员；这种效应在所有研究的储存部位（肝脏、暗色肌肉、肠系膜脂肪）都很明显。总脂质浓度或总组织质量（肠系膜脂肪）的降低伴随着脂肪酶活性增加，通常导致组织三酰甘油含量减少。银化幼鱼似乎对PRL处理不敏感。垂体切除的银化幼鱼（其肝脏脂肪酶活性通常较高）表现出低水平的肝脏脂肪酶活性。补充皮质醇可使酶活性恢复到与假手术对照组大致相同的水平。补充GH可恢复脂肪酶活性，但未恢复到假手术对照组观察到的水平。这些结果表明，T4、皮质醇、GH和PRL均通过增强脂解作用刺激发育中鲑鱼的脂质动员，并表明T4、皮质醇、GH和PRL是导致与银化相关的脂质消耗的因素之一。
