Björnsson B T, Young G, Lin R J, Deftos L J, Bern H A
Department of Zoology and Cancer Research Laboratory, University of California, Berkeley 94720.
Gen Comp Endocrinol. 1989 Jun;74(3):346-54. doi: 10.1016/s0016-6480(89)80030-9.
In order to examine the dynamics of ion regulation, osmoregulation, and plasma calcitonin during the parr-smolt transformation (smoltification), blood and gill tissue were collected from yearling coho salmon, Oncorhynchus kisutch, from February to October. Fish were kept in fresh water (FW) throughout this period. In addition, fish were exposed to seawater (SW) at the peak of smoltification in mid-April, and samples from these fish were collected until July. Plasma osmolality, gill Na+,K+-ATPase activity, plasma levels of calcitonin, and free and total calcium and magnesium were measured. SW adaptability of FW fish was assessed throughout the study by measurements of plasma osmolality following a 24-hr exposure to seawater. The greatest hypoosmoregulatory ability occurred in April-May, although SW-adapted fish had higher plasma osmolality than FW-adapted fish at all times. Gill Na+,K+-ATPase activity in FW-adapted fish increased from April to June and increased rapidly following exposure of fish to SW, and remained elevated in SW-adapted fish. Free plasma calcium and magnesium levels increased following SW exposure, but returned to prior levels within 1 week. Netting and confinement stress during sampling caused an increase in plasma osmolality and free calcium and magnesium levels in both FW- and SW-adapted fish. Changes in hypoosmoregulatory ability during smoltification and SW adaptation were correlated with changes in gill Na+,K+-ATPase activity. A sharp transitory peak in plasma calcitonin levels occurred early in smoltification (March) and in SW-adapted fish in June. Plasma calcitonin levels gradually increased in FW-adapted fish during the period of desmoltification. However, no change in plasma calcitonin levels occurred during SW-induced hypercalcemia, suggesting that the hormone does not play a major role in short-term plasma calcium regulation in coho salmon.
为了研究银大麻哈鱼从幼鲑向稚鲑转变（即稚鲑化）过程中离子调节、渗透压调节及血浆降钙素的动态变化，于2月至10月从一岁的银大麻哈鱼（Oncorhynchus kisutch）采集血液和鳃组织样本。在此期间，鱼一直饲养在淡水（FW）中。此外，在4月中旬稚鲑化高峰期将鱼暴露于海水中（SW），并收集这些鱼的样本直至7月。测定了血浆渗透压、鳃Na⁺,K⁺-ATP酶活性、血浆降钙素水平以及游离钙和总钙、镁水平。在整个研究过程中，通过测定暴露于海水24小时后的血浆渗透压来评估淡水鱼对海水的适应性。尽管适应海水的鱼在任何时候血浆渗透压都高于适应淡水的鱼，但最大的低渗调节能力出现在4月至5月。适应淡水的鱼鳃Na⁺,K⁺-ATP酶活性从4月到6月增加，在鱼暴露于海水后迅速增加，并在适应海水的鱼中保持升高。暴露于海水后，血浆游离钙和镁水平升高，但在1周内恢复到先前水平。采样期间的捕捞和限制应激导致适应淡水和适应海水的鱼血浆渗透压以及游离钙和镁水平升高。稚鲑化和适应海水过程中低渗调节能力的变化与鳃Na⁺,K⁺-ATP酶活性的变化相关。血浆降钙素水平在稚鲑化早期（3月）和6月适应海水的鱼中出现急剧短暂的峰值。在脱稚鲑化期间，适应淡水的鱼血浆降钙素水平逐渐升高。然而，在海水诱导的高钙血症期间，血浆降钙素水平没有变化，这表明该激素在银大麻哈鱼短期血浆钙调节中不起主要作用。
