Björnsson B T, Yamauchi K, Nishioka R S, Deftos L J, Bern H A
Department of Zoology, University of California, Berkeley 94720.
Gen Comp Endocrinol. 1987 Dec;68(3):421-30. doi: 10.1016/0016-6480(87)90081-5.
This study investigates the effects of hypophysectomy and subsequent hormone replacement therapy upon the hormonal and osmoregulatory status of coho salmon, Oncorhynchus kisutch, in 7% seawater (SW) and SW. Following hypophysectomy, coho salmon were injected every 2 days for 8 days with thyroxine, growth hormone, and cortisol, alone or in combinations, and sampled 2 days after the final injection. Increased environmental salinity raises plasma sodium, calcium, and magnesium levels, as well as plasma osmolality. Cortisol is hypercalcemic and thyroxine is hypocalcemic in hypophysectomized salmon, but it is unclear whether these effects are due directly to calcium regulation or are the consequence of general effects on the plasma osmotic/ionic balance. Growth hormone and thyroxine together, but not separately, decrease and increase magnesium levels, at low and high environmental salinities, respectively, indicating a complex endocrine control of plasma magnesium. Gill Na+, K+-ATPase activity in hypophysectomized salmon is stimulated by growth hormone and cortisol, but inhibited by thyroxine and raised environmental salinity. This implies a complex endocrine control and indicates that hormonal support is needed to sustain or raise gill Na+, K+-ATPase activity in seawater. Increased environmental salinity induces elevation of plasma cortisol levels in apparent absence of pituitary control, indicating that the interrenals may respond to changes in external and/or internal environment, either directly or indirectly through extrapituitary hormonal or nervous control. Cortisol is a potent inhibitor of calcitonin secretion, as seen by the large decrease in plasma calcitonin levels in cortisol-treated hypophysectomized fish. The study was carried out at a time when thyroxine plasma levels were low. These basal levels were not affected by hypophysectomy, possibly indicating a basal release of thyroxine from the thyroid without stimulatory support of the pituitary gland.
本研究调查了垂体切除及随后的激素替代疗法对银大麻哈鱼（Oncorhynchus kisutch）在7%海水（SW）和海水环境下激素及渗透调节状态的影响。垂体切除后，银大麻哈鱼每隔2天注射甲状腺素、生长激素和皮质醇，单独注射或联合注射，持续8天，并在最后一次注射后2天进行取样。环境盐度升高会提高血浆钠、钙和镁水平以及血浆渗透压。在垂体切除的鲑鱼中，皮质醇具有升血钙作用，甲状腺素具有降血钙作用，但尚不清楚这些作用是直接由于钙调节，还是对血浆渗透/离子平衡的一般影响的结果。生长激素和甲状腺素共同作用（而非单独作用），分别在低环境盐度和高环境盐度下降低和升高镁水平，表明血浆镁存在复杂的内分泌控制。垂体切除的鲑鱼鳃中Na⁺,K⁺-ATP酶活性受生长激素和皮质醇刺激，但受甲状腺素和升高的环境盐度抑制。这意味着存在复杂的内分泌控制，并表明在海水中维持或提高鳃Na⁺,K⁺-ATP酶活性需要激素支持。在明显缺乏垂体控制的情况下，环境盐度升高会导致血浆皮质醇水平升高，这表明肾上腺可能直接或通过垂体外激素或神经控制对外部和/或内部环境变化作出反应。皮质醇是降钙素分泌的有效抑制剂，这在皮质醇处理的垂体切除鱼血浆降钙素水平大幅下降中可见。该研究是在血浆甲状腺素水平较低时进行的。这些基础水平不受垂体切除影响，这可能表明甲状腺在没有垂体刺激支持的情况下会基础释放甲状腺素。
