Kiilerich Pia, Kristiansen Karsten, Madsen Steffen S
Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Gen Comp Endocrinol. 2007 Jun-Jul;152(2-3):295-303. doi: 10.1016/j.ygcen.2006.12.018. Epub 2006 Dec 30.
This is the first study to report concurrent dynamics in mRNA expression of growth hormone receptor (GHR), prolactin receptor (PRLR), gluco- and mineralocorticoid receptor (GR and MR) and the 11beta-hydroxysteroid dehydrogenase type-2 enzyme (11beta-HSD2) in Atlantic salmon (Salmo salar) gill during smoltification. Transcript levels were analysed by quantitative PCR in fresh water (FW) fish and after a 24-h salt water (SW) challenge. GHR transcript levels increased concurrent with gill Na(+),K(+)-ATPase activity in FW fish consistent with the SW-adaptive role of GH. SW-transfer induced an increased GHR expression levels in the early stages of smoltification but a decrease in expression at the peak of smoltification. PRLR transcript levels decreased steadily during smoltification in agreement with the recognized hyper-osmoregulatory role of PRL. Surprisingly, PRLR levels increased after SW transfer during the course of smoltification. GR mRNA levels were low early on during smoltification but increased at the peak of smoltification and remained high during de-smoltification, indicative of increased cortisol signalling at this point. Coherently, SW transfer increased GR levels to smolt levels prior to the smoltification peak. 11beta-HSD2 levels increased at the smoltification peak and MR levels increased during de-smoltification, suggesting a need for protection of MR from cortisol signalling during smoltification. This is supported by the fact that SW-transfer results in a profound up-regulation of 11beta-HSD2, whereas SW transfer down-regulates MR levels. The study concludes that GR and MR may have distinctive roles in developing hypo- and hyper-osmoregulatory mechanisms during smoltification and de-smoltification, respectively.
这是第一项报告大西洋鲑（Salmo salar）在洄游期间鳃中生长激素受体（GHR）、催乳素受体（PRLR）、糖皮质激素和盐皮质激素受体（GR和MR）以及11β-羟基类固醇脱氢酶2型（11β-HSD2）mRNA表达同步动态变化的研究。通过定量PCR分析了淡水（FW）鱼和经过24小时盐水（SW）刺激后的转录水平。GHR转录水平在FW鱼中与鳃Na(+)，K(+)-ATP酶活性同时增加，这与GH的SW适应性作用一致。SW转移在洄游早期诱导GHR表达水平增加，但在洄游高峰期表达下降。PRLR转录水平在洄游期间稳步下降，这与PRL公认的高渗调节作用一致。令人惊讶的是，在洄游过程中SW转移后PRLR水平增加。GR mRNA水平在洄游早期较低，但在洄游高峰期增加，并在去洄游期间保持较高水平，表明此时皮质醇信号增加。连贯地，SW转移在洄游高峰之前将GR水平提高到洄游水平。11β-HSD2水平在洄游高峰期增加，MR水平在去洄游期间增加，这表明在洄游期间需要保护MR免受皮质醇信号的影响。SW转移导致11β-HSD2显著上调，而SW转移下调MR水平，这一事实支持了这一点。该研究得出结论，GR和MR可能分别在洄游和去洄游过程中发展低渗和高渗调节机制中发挥独特作用。
