Krumschnabel G, Biasi C, Schwarzbaum P J, Wieser W
Abteilung für Okophysiologie, Universität Innsbruck, Austria.
J Comp Physiol B. 1997 May;167(4):280-6. doi: 10.1007/s003600050075.
Short- and long-term effects of temperature on ion flux and energy turnover were studied in hepatocytes from thermally acclimated trout and roach. In trout hepatocytes K+ efflux was insensitive towards acute exposure to low temperature but was downregulated during cold acclimation of the fish so as to balance the uncompensated decreased K+ (Rb+) uptake of the cells. In contrast, both K+ (Rb+) uptake and K+ efflux of roach hepatocytes were temperature sensitive in the short term. These acute effects, however, were offset during cold acclimation by a near perfect compensation of both fluxes leading to re-establishment of ion flux homeostasis at the original level. Our findings, based on a new method permitting the simultaneous monitoring of K+ efflux and uptake in the same cell population, provide experimental verification of two of the three possible strategies, recently discussed by Cossins et al. (1995), by which the ionic steady state of fish cells may adjust to acute and chronic temperature change. By comparing hepatocytes from two groups of trout, one kept on a maintenance diet (ration I), the other fed ad libitum (ration II), we discovered striking effects of nutritional state on the absolute levels as well as on the temperature relationships of K+ uptake and protein synthetic activity. Both of these functions in the hepatocytes increased in the ration II fed as compared to the ration I fed trouts, but the increase of protein synthetic activity was greater and more uniform at the three experimental temperatures than that of K+ uptake. Moreover, protein synthetic activity proved to be considerably more temperature sensitive than K+ uptake and, in contrast to the latter, showed a compensatory response after cold acclimation.
研究了温度对经热适应的鳟鱼和拟鲤肝细胞离子通量和能量转换的短期和长期影响。在鳟鱼肝细胞中，钾离子外流对急性低温暴露不敏感，但在鱼的冷适应过程中会下调，以平衡细胞中未补偿的钾离子（铷离子）摄取减少。相比之下，拟鲤肝细胞的钾离子（铷离子）摄取和钾离子外流在短期内对温度敏感。然而，在冷适应过程中，这些急性影响被两种通量几乎完美的补偿所抵消，导致离子通量稳态在原始水平重新建立。我们的研究结果基于一种新方法，该方法允许在同一细胞群体中同时监测钾离子外流和摄取，为最近Cossins等人（1995年）讨论的三种可能策略中的两种提供了实验验证，通过这些策略，鱼细胞的离子稳态可以适应急性和慢性温度变化。通过比较两组鳟鱼的肝细胞，一组维持定量喂食（日粮I），另一组自由采食（日粮II），我们发现营养状态对钾离子摄取和蛋白质合成活性的绝对水平以及温度关系有显著影响。与喂食日粮I的鳟鱼相比，喂食日粮II的鳟鱼肝细胞中的这两种功能都有所增加，但在三个实验温度下，蛋白质合成活性的增加比钾离子摄取的增加更大且更均匀。此外，蛋白质合成活性被证明比钾离子摄取对温度更敏感，与后者不同的是，在冷适应后表现出补偿反应。
