Sardella Brian A, Kültz Dietmar
Department of Animal Science, University of California, Davis, CA 95616, USA.
J Comp Physiol B. 2009 Apr;179(3):383-90. doi: 10.1007/s00360-008-0321-5. Epub 2008 Dec 10.
The green sturgeon is a long-lived, highly migratory species with populations that are currently listed as threatened. Their anadromous life history requires that they make osmo- and ionoregulatory adjustments in order to maintain a consistent internal milieu as they move between fresh-, brackish-, and seawater. We acclimated juvenile green sturgeon (121 +/- 10.0 g) to 0 (freshwater; FW), 15 (estuarine; EST), and 24 g/l (SF Bay water; BAY) at 18 degrees C for 2 weeks and measured the physiological and biochemical responses with respect to osmo- and ionoregulatory mechanisms. Plasma osmolality in EST- and BAY-acclimated sturgeon was elevated relative to FW-acclimated sturgeon (P < 0.01), but there was no difference in muscle water content or abundance of stress proteins. Branchial Na(+), K(+)-ATPase (NKA) activity was also unchanged, but abundance within mitochondrion-rich cells (MRC) was greater in BAY-acclimated sturgeon (P < 0.01). FW-acclimated sturgeon had the greatest NKA abundance when assessed at the level of the entire tissue (P < 0.01), but there were no differences in v-type H(+)ATPase (VHA) activity or abundance between salinities. The Na(+), K(+), 2Cl(-) co-transporter (NKCC) was present in FW-acclimated sturgeon gills, but the overall abundance was lower relative to sturgeon in EST or BAY water (P < 0.01) where this enzyme is crucial to hypoosmoregulation. Branchial caspase 3/7 activity was significantly affected by acclimation salinity (P < 0.05) where the overall trend was for activity to increase with salinity as has been commonly observed in teleosts. Sturgeon of this age/size class were able to survive and acclimate following a salinity transfer with minimal signs of osmotic stress. The presence of the NKCC in FW-acclimated sturgeon may indicate the development of SW-readiness at this age/size.
绿鲟是一种寿命长、洄游性强的物种，其种群目前被列为受威胁物种。它们的溯河洄游生活史要求它们进行渗透压和离子调节调整，以便在淡水、咸淡水和海水中移动时维持一致的内部环境。我们将幼年绿鲟（121±10.0克）在18摄氏度下分别适应0（淡水；FW）、15（河口；EST）和24克/升（旧金山湾水；BAY）的盐度2周，并测量了与渗透压和离子调节机制相关的生理和生化反应。与适应FW的绿鲟相比，适应EST和BAY的绿鲟血浆渗透压升高（P<0.01），但肌肉含水量或应激蛋白丰度没有差异。鳃部Na(+)、K(+)-ATP酶（NKA）活性也没有变化，但适应BAY的绿鲟富含线粒体的细胞（MRC）中的NKA丰度更高（P<0.01）。在整个组织水平评估时，适应FW的绿鲟NKA丰度最高（P<0.01），但不同盐度之间v型H(+)ATP酶（VHA）活性或丰度没有差异。适应FW的绿鲟鳃中存在Na(+)、K(+)、2Cl(-)协同转运蛋白（NKCC），但其总体丰度相对于EST或BAY水中的绿鲟较低（P<0.01），而该酶对低渗调节至关重要。鳃部半胱天冬酶3/7活性受适应盐度的显著影响（P<0.05），总体趋势是活性随盐度增加，这在硬骨鱼中很常见。这个年龄/大小级别的绿鲟在盐度转移后能够存活并适应，渗透压应激迹象最小。适应FW的绿鲟中NKCC的存在可能表明该年龄/大小的绿鲟已具备适应海水的能力。
