Fish Endocrinology Laboratory, Department of Zoology/Zoophysiology, University of Gothenburg, Box 463, SE 40530 Gothenburg, Sweden.
Gen Comp Endocrinol. 2010 May 15;167(1):77-85. doi: 10.1016/j.ygcen.2010.02.011. Epub 2010 Feb 18.
Growth hormone in fish regulates many important physiological processes including growth, metabolism and potentially reproduction. In salmonid fish, GH secretion is episodic with irregularly spaced GH peaks. Plasma GH reflects secretion episodes as well as the clearance rate of the hormone, and plasma levels may thus not always reflect the level of activation of the GH axis. This study measured the production dynamics of GH over a 17-month period in sexually maturing female Atlantic salmon which included final maturation and spawning. For the first time, the level of pituitary GH mRNA, pituitary GH protein and plasma GH protein were analyzed concurrently in the same individuals. mRNA and protein were extracted in parallel from the same samples with subsequent real time quantitative PCR to measure mRNA transcripts and radioimmunoassay to measure pituitary and plasma GH protein. Further, the effects of photoperiod manipulation on these parameters were studied. The results show no correlation between mRNA and protein levels except at some time points, and indicate that it is inappropriate to correlate pooled temporal data and averages in time series unless the relationship among the variables is stable over time. The results indicate complex and shifting relationships between pituitary GH mRNA expression, pituitary GH content and plasma GH levels, which could result from changes in clearance rather than secretion rate at different times and its episodic secretion. The study also suggests that there is a functionally important activation of the GH system during spring leading up to maturation and spawning.
生长激素在鱼类中调节许多重要的生理过程，包括生长、代谢和潜在的繁殖。在鲑鱼中，GH 的分泌是间歇性的，具有不规律的 GH 峰间隔。血浆 GH 反映了激素的分泌情况和清除率，因此血浆水平并不总是反映 GH 轴的激活水平。本研究在性成熟的雌性大西洋鲑鱼中测量了 17 个月内 GH 的产生动态，包括最终成熟和产卵。这是首次同时在同一批个体中分析垂体 GH mRNA、垂体 GH 蛋白和血浆 GH 蛋白的水平。从相同的样本中同时提取 mRNA 和蛋白质，随后进行实时定量 PCR 以测量 mRNA 转录物，以及放射免疫测定法测量垂体和血浆 GH 蛋白。此外，还研究了光周期操纵对这些参数的影响。结果表明，mRNA 和蛋白质水平之间没有相关性，除非在某些时间点，这表明除非变量之间的关系在时间上是稳定的，否则将时间序列中的时间数据和平均值进行平均是不合适的。结果表明，垂体 GH mRNA 表达、垂体 GH 含量和血浆 GH 水平之间存在复杂且不断变化的关系，这可能是由于不同时间清除率而不是分泌率的变化以及其间歇性分泌所致。该研究还表明，在成熟和产卵之前的春季，GH 系统存在功能上重要的激活。
