Haddad P, Thalhammer T, Graf J
Institute of General and Experimental Pathology, University of Vienna, Austria.
Am J Physiol. 1989 Mar;256(3 Pt 1):G563-9. doi: 10.1152/ajpgi.1989.256.3.G563.
Net hepatic uptake and release of K+ were studied in the isolated-perfused rat liver subjected to a 10-min period of hyperosmotic stress by addition of 80 mM mannitol or sucrose to the perfusing solution. Bile flow and effluent Na+, K+, and Ca2+ activities were monitored throughout. Upon initiation of hypertonic stress, a sharp transient dilution of effluent ion activities indicated hepatic water losses that were larger and occurred more rapidly with sucrose than with mannitol. During continuous hyperosmotic perfusion, portocaval differences in K+ uncovered a steady net influx of the ion into the liver that reached a higher maximum and led to a greater accumulation in experiments with sucrose compared with mannitol. This hepatic K+ uptake was completely blocked by 1 mM ouabain. Upon return to isotonic conditions, a sharp transient concentration of effluent ion activities suggested hepatic water uptake that was again more rapid and pronounced in sucrose- than mannitol-treated livers. This was followed by a transient phase of net hepatic K+ release whose magnitude and duration were proportional to the water movements induced by the removal of each carbohydrate. Administration of 2 mM Ba2+ abolished this K+ efflux. These results indicate that mannitol equilibrates between extra- and intracellular compartments, whereas sucrose apparently does not. The data also suggest that net movements of K+ may be involved in the regulatory volume responses induced by hyperosmotic stress and return to normal tonicity, respectively.
通过向灌注溶液中添加80 mM甘露醇或蔗糖，对经受10分钟高渗应激的离体灌注大鼠肝脏中钾离子（K⁺）的净肝摄取和释放进行了研究。在整个过程中监测胆汁流量以及流出液中钠离子（Na⁺）、钾离子和钙离子（Ca²⁺）的活性。在高渗应激开始时，流出液离子活性的急剧短暂稀释表明肝脏失水，与甘露醇相比，蔗糖引起的失水更大且发生得更快。在持续高渗灌注期间，门静脉与腔静脉之间钾离子的差异揭示了该离子持续稳定地净流入肝脏，与甘露醇相比，在蔗糖实验中达到更高的最大值并导致更大的积累。这种肝脏对钾离子的摄取被1 mM哇巴因完全阻断。回到等渗条件后，流出液离子活性的急剧短暂浓缩表明肝脏吸水，在蔗糖处理的肝脏中再次比甘露醇处理的肝脏更快且更明显。随后是肝脏钾离子净释放的短暂阶段，其幅度和持续时间与每种碳水化合物去除所引起的水移动成比例。给予2 mM钡离子（Ba²⁺）消除了这种钾离子外流。这些结果表明，甘露醇可在细胞外和细胞内区室之间达到平衡，而蔗糖显然不能。数据还表明，钾离子的净移动可能分别参与了高渗应激诱导的调节性容积反应以及恢复到正常张力的过程。
