Gonzalez-Cabrera P J, Dowd F, Pedibhotla V K, Rosario R, Stanley-Samuelson D, Petzel D
Department of Pharmacology, School of Medicine, Creighton University, Omaha, NE 68178, USA.
J Exp Biol. 1995 Nov;198(Pt 11):2279-91. doi: 10.1242/jeb.198.11.2279.
Serum osmolality and serum inorganic ion concentrations were studied in two antarctic fish species, Trematomus bernacchii and T. newnesi, during 5 weeks of acclimation to 4 degrees C and compared with control values for groups acclimated to -1.5 degrees C. Acclimation to 4 degrees C significantly decreased the serum osmolality of both species, thereby increasing their seawater-to-extracellular fluid (ECF) osmotic gradient. The decline in osmolality with acclimation to 4 degrees C was accompanied by significant and rapid losses of Na+ and Cl- during the first 14 days of acclimation and was maintained throughout the study period. At day 35 of acclimation, the lipid composition and microsomal Na+/K(+)-ATPase specific activities at 4 degrees C and 37 degrees C were determined in membranes from gill, kidney, liver and muscle tissues. No warm-induced decrease in fatty acid unsaturation was found in the tissues of either species. In the gills and kidneys of both species, the Na+/K(+)-ATPase activities assayed at 4 degrees C were increased after acclimation to 4 degrees C. The Na+/K(+)-ATPase activities at 37 degrees C increased at the higher acclimation temperature in T. newnesi kidneys and T. bernacchii gills, but in both species there was no compensation to temperature in the liver, regardless of assay temperature. Muscle Na+/K(+)-ATPase activity decreased in response to warm-acclimation in T. bernacchii and T. newnesi assayed at 4 degrees C and 37 degrees C, respectively. During acclimation to 4 degrees C, the discontinuity in the Arrhenius plot of the Na+/K(+)-ATPase activities of T. newnesi gill moved to a lower temperature, whereas that of kidney remained unchanged. The results indicate that acclimation to 4 degrees C induced a decrease in serum osmolality which resulted from the positive compensation of Na+/K(+)-ATPase in osmoregulatory tissues. The enhancement in Na+/K(+)-ATPase activity at 4 degrees C suggests that energy expenditure in antarctic fish may be lessened, in part, by maintaining a reduced seawater-to-ECF osmotic gradient.
在将两种南极鱼类——伯氏南极鱼（Trematomus bernacchii）和纽氏南极鱼（T. newnesi）驯化至4℃的5周时间内，对其血清渗透压和血清无机离子浓度进行了研究，并与驯化至-1.5℃的对照组数值进行了比较。驯化至4℃显著降低了两种鱼类的血清渗透压，从而增大了它们海水与细胞外液（ECF）的渗透梯度。在驯化的前14天，随着驯化至4℃，渗透压下降，同时伴随着Na⁺和Cl⁻的显著快速流失，且在整个研究期间一直保持。在驯化的第35天，测定了4℃和37℃时鳃、肾、肝和肌肉组织膜中的脂质组成以及微粒体Na⁺/K⁺-ATP酶的比活性。在这两种鱼类的组织中均未发现因温度升高导致的脂肪酸不饱和度降低。在两种鱼类的鳃和肾中，4℃下测定的Na⁺/K⁺-ATP酶活性在驯化至4℃后有所增加。在较高的驯化温度下，纽氏南极鱼肾和伯氏南极鱼鳃中37℃时的Na⁺/K⁺-ATP酶活性增加，但在这两种鱼类中，无论测定温度如何，肝脏中的酶活性均未随温度而发生补偿性变化。在4℃和37℃下测定时，伯氏南极鱼和纽氏南极鱼的肌肉Na⁺/K⁺-ATP酶活性分别因暖驯化而降低。在驯化至4℃期间，纽氏南极鱼鳃的Na⁺/K⁺-ATP酶活性Arrhenius图中的不连续点移至较低温度，而肾的不连续点保持不变。结果表明，驯化至4℃导致血清渗透压降低，这是由于渗透调节组织中Na⁺/K⁺-ATP酶的正向补偿作用。4℃时Na⁺/K⁺-ATP酶活性的增强表明，南极鱼类的能量消耗可能部分通过维持降低的海水与ECF渗透梯度而减少。
