Richman N H, Zaugg W S
Gen Comp Endocrinol. 1987 Feb;65(2):189-98. doi: 10.1016/0016-6480(87)90165-1.
Salmonid species which undergo smoltification show a concurrent enhancement in saltwater (SW) osmoregulatory ability. This developmental change is marked by an increase in SW tolerance and gill Na+,K+-ATPase activity which appears to result, in part, from an increase in gill chloride cell density. Previous studies have suggested that cortisol and growth hormone (GH) may stimulate SW osmoregulatory mechanisms in salmonids. In this study, these hormones were examined for their ability to induce smoltification-associated osmoregulatory changes in pre- and desmoltified coho salmon (Oncorhynchus kisutch). Cortisol treatment for 12 days increased gill Na+,K+-ATPase activity in presmolts and gill residual (Na+,K+-independent) ATPase activity in both groups. Chloride cell density in presmolt primary and secondary lamellae and in desmolt secondary lamellae was increased as well. The rise in plasma sodium levels in fish transferred to SW was reduced only in desmolts. Treatment with bovine GH for 12-13 days increased gill Na+,K+-ATPase activity in presmolts and in desmolts. However, GH treatment in either group did not increase gill residual ATPase activity or alter plasma sodium levels in SW-transferred animals. Gill chloride cell density in presmolts also was unaffected (desmolts were not examined). Thus, both cortisol and GH are partially able to produce changes similar to those observed during smoltification. The contrasting effects of these hormones on gill chloride cell density and gill residual ATPase activity suggest that cortisol may stimulate chloride cell proliferation and/or differentiation, whereas GH may act specifically to increase gill Na+,K+-ATPase activity.
经历了变态的鲑科鱼类在海水渗透调节能力方面同时得到增强。这种发育变化的标志是海水耐受性和鳃Na⁺,K⁺-ATP酶活性增加，这似乎部分是由于鳃氯细胞密度增加所致。先前的研究表明，皮质醇和生长激素（GH）可能刺激鲑科鱼类的海水渗透调节机制。在本研究中，检测了这些激素在未变态和变态后的银大麻哈鱼（Oncorhynchus kisutch）中诱导与变态相关的渗透调节变化的能力。皮质醇处理12天增加了未变态幼鱼的鳃Na⁺,K⁺-ATP酶活性以及两组鱼鳃的残余（不依赖Na⁺,K⁺）ATP酶活性。未变态幼鱼初级和次级鳃小片以及变态后次级鳃小片的氯细胞密度也增加了。转移到海水中的鱼血浆钠水平的升高仅在变态后幼鱼中有所降低。用牛生长激素处理12 - 13天增加了未变态幼鱼和变态后幼鱼的鳃Na⁺,K⁺-ATP酶活性。然而，两组中的生长激素处理均未增加鳃残余ATP酶活性，也未改变转移到海水中的动物的血浆钠水平。未变态幼鱼的鳃氯细胞密度也未受影响（未检测变态后幼鱼）。因此，皮质醇和生长激素都部分能够产生与变态过程中观察到的类似变化。这些激素对鳃氯细胞密度和鳃残余ATP酶活性的不同影响表明，皮质醇可能刺激氯细胞增殖和/或分化，而生长激素可能专门作用于增加鳃Na⁺,K⁺-ATP酶活性。
