Fedorow C A, Churchill T A, Kneteman N M
Surgical-Medical Research Institute, University of Alberta, Edmonton, Canada.
J Comp Physiol B. 1998 Dec;168(8):555-61. doi: 10.1007/s003600050177.
Many lower vertebrates (reptilian and amphibian species) are capable of surviving natural episodes of hypoxia and hypothermia. It is by specific metabolic adaptations that anurans are able to tolerate prolonged exposure to harsh environmental stresses. In this study, it was hypothesized that livers from an aquatic frog would possess an inherent metabolic ability to sustain high levels of ATP in an isolated organ system, providing insight into a metabolic system that is well-adapted for low temperature in vitro organ storage. Frogs of the species, R. pipiens were acclimated at 20 degrees C and at 5 degrees C. Livers were preserved using a clinical preservation solution after flushing. Livers from 20 degrees C-acclimated frogs were stored at 20 degrees C and 5 degrees C and livers from 5 degrees C-acclimated frogs were stored at 5 degrees C. The results indicated that hepatic adenylate status was maintained for 96 h during 5 degrees C storage, but not longer than 4-10 h during 20 degrees C storage. In livers from 5 degrees C-acclimated animals subjected to 5 degrees C storage, ATP was maintained at 100% throughout the 96-h period. Warm acclimation (20 degrees C) and 20 degrees C storage resulted in poorer maintenance of ATP; energy charge values dropped to 0.50 within 2 h and by 24 h, only 24% of control ATP remained. Lactate levels remained less than 25 mumol/g dry weight in all 5 degrees C-stored livers; 20 degrees C-stored livers exhibited greater accumulation of this anaerobic endproduct (lactate reached 45-50 mumol/g by 10 h). The data imply that hepatic adenylate status is largely dependent on exposure to hypothermic hypoxia and although small amounts of ATP were accounted for by anaerobic glycolysis, there must have been either a substantial reduction in cellular energy-utilization or an efficient use of low oxygen tensions.
许多低等脊椎动物（爬行动物和两栖动物物种）能够在自然发生的缺氧和低温环境中存活。通过特定的代谢适应，无尾两栖类动物能够耐受长时间暴露于恶劣的环境压力之下。在本研究中，我们假设水生蛙的肝脏在离体器官系统中具有维持高水平三磷酸腺苷（ATP）的内在代谢能力，这有助于深入了解一种非常适合低温体外器官保存的代谢系统。将北美豹蛙（R. pipiens）分别在20℃和5℃下进行驯化。冲洗后，使用临床保存溶液保存肝脏。将20℃驯化的青蛙的肝脏分别在20℃和5℃下储存，将5℃驯化的青蛙的肝脏在5℃下储存。结果表明，在5℃储存期间，肝脏腺苷酸状态维持了96小时，但在20℃储存期间不超过4 - 10小时。在5℃驯化的动物的肝脏在5℃下储存时，在整个96小时内ATP维持在100%。温暖驯化（20℃）和20℃储存导致ATP维持较差；能量电荷值在2小时内降至0.50，到24小时时，仅剩余对照ATP的24%。在所有5℃储存的肝脏中，乳酸水平保持低于25μmol/g干重；20℃储存的肝脏中这种厌氧终产物积累更多（到10小时时乳酸达到45 - 50μmol/g）。数据表明肝脏腺苷酸状态在很大程度上取决于低温缺氧暴露，虽然无氧糖酵解产生了少量ATP，但细胞能量利用必定大幅减少或对低氧张力进行了有效利用。
