Breves Jason P, Fujimoto Chelsea K, Phipps-Costin Silas K, Einarsdottir Ingibjörg E, Björnsson Björn Thrandur, McCormick Stephen D
Department of Biology, Skidmore College, 815 N Broadway, Saratoga Springs, 12866, NY, USA.
Fish Endocrinology Laboratory, Department of Biological and Environmental Sciences, University of Gothenburg, Box 463, SE-40530, Gothenburg, Sweden.
BMC Physiol. 2017 Jan 18;17(1):2. doi: 10.1186/s12899-017-0028-5.
In preparation for migration from freshwater to marine habitats, Atlantic salmon (Salmo salar L.) undergo smoltification, a transformation that includes the acquisition of hyposmoregulatory capacity. The growth hormone (Gh)/insulin-like growth-factor (Igf) axis promotes the development of branchial ionoregulatory functions that underlie ion secretion. Igfs interact with a suite of Igf binding proteins (Igfbps) that modulate hormone activity. In Atlantic salmon smolts, igfbp4,-5a,-5b1,-5b2,-6b1 and-6b2 transcripts are highly expressed in gill. We measured mRNA levels of branchial and hepatic igfbps during smoltification (March, April, and May), desmoltification (July) and following seawater (SW) exposure in March and May. We also characterized parallel changes in a broad suite of osmoregulatory (branchial Na/K-ATPase (Nka) activity, Na /K /2Cl cotransporter 1 (nkcc1) and cystic fibrosis transmembrane regulator 1 (cftr1) transcription) and endocrine (plasma Gh and Igf1) parameters.
Indicative of smoltification, we observed increased branchial Nka activity, nkcc1 and cftr1 transcription in May. Branchial igfbp6b1 and -6b2 expression increased coincidentally with smoltification. Following a SW challenge in March, igfbp6b1 showed increased expression while igfbp6b2 exhibited diminished expression. igfbp5a,-5b1 and-5b2 mRNA levels did not change during smolting, but each had lower levels following a SW exposure in March.
Salmonids express an especially large suite of igfbps. Our data suggest that dynamic expression of particular igfbps accompanies smoltification and SW challenges; thus, transcriptional control of igfbps may provide a mechanism for the local modulation of Igf activity in salmon gill.
为了准备从淡水栖息地迁移到海洋栖息地，大西洋鲑（Salmo salar L.）经历了幼鲑化过程，这一转变包括获得低渗调节能力。生长激素（Gh）/胰岛素样生长因子（Igf）轴促进鳃离子调节功能的发育，而离子调节功能是离子分泌的基础。Igfs与一系列调节激素活性的Igf结合蛋白（Igfbps）相互作用。在大西洋鲑幼鲑中，igfbp4、-5a、-5b1、-5b2、-6b1和-6b2转录本在鳃中高度表达。我们测量了幼鲑化期间（3月、4月和5月）、逆幼鲑化期间（7月）以及3月和5月海水（SW）暴露后鳃和肝脏中igfbps的mRNA水平。我们还对一系列渗透调节（鳃钠钾ATP酶（Nka）活性、钠/钾/2氯共转运蛋白1（nkcc1）和囊性纤维化跨膜调节因子1（cftr1）转录）和内分泌（血浆Gh和Igf1）参数的平行变化进行了表征。
作为幼鲑化的指标，我们观察到5月鳃Nka活性、nkcc1和cftr1转录增加。鳃igfbp6b1和-6b2表达与幼鲑化同时增加。3月海水挑战后，igfbp6b1表达增加，而igfbp6b2表达减少。igfbp5a、-5b1和-5b2 mRNA水平在幼鲑化期间没有变化，但在3月海水暴露后均较低。
鲑科鱼类表达了特别大量的igfbps。我们的数据表明，特定igfbps的动态表达伴随着幼鲑化和海水挑战；因此，igfbps的转录控制可能为鲑鱼鳃中Igf活性的局部调节提供一种机制。
