Department of Physiology, Faculty of Medicine, University of Manitoba, Institute of Cardiovascular Sciences, St Boniface General Hospital Research Centre, Winnipeg, MB R2H 2A6, Canada.
Can J Physiol Pharmacol. 2010 Mar;88(3):388-97. doi: 10.1139/Y10-012.
Depression in cardiac performance due to ischemia-reperfusion (I/R) injury is associated with the development of oxidative stress and decreased sarcolemmal (SL) Na+/K+-ATPase activity. Since both I/R and oxidative stress have been reported to promote the occurrence of intracellular Ca2+ overload and activate proteases such as calpain, this study was undertaken to investigate whether the activation of calpain in I/R hearts is associated with alterations in the SL Na+/K+-ATPase activity and its isoform content. For this purpose, isolated rat hearts treated with and without 2 different calpain inhibitors (leupeptin and MDL28170) were subjected to 30 min ischemia followed by 60 min of reperfusion, and the cardiac function, SL Na+/K+-ATPase activity, Na+/K+-ATPase isoform protein content, and calpain activity were measured. The I/R-induced depressions in cardiac function, Na+/K+-ATPase activity, and protein content of Na+/K+-ATPase isoforms were associated with an increase in calpain activity , but were prevented by treatment of hearts with leupeptin. Incubation of SL membranes with calpain decreased the Na+/K+-ATPase activity and protein content of its isoforms; these changes were also attenuated by leupeptin. The I/R-induced alterations in cardiac function and the activity of SL Na+/K+-ATPase and calpain were Ca2+-dependent and were prevented by MDL28170, a specific inhibitor of calpain. The I/R-induced translocation of calpain isoforms (I and II) from the cytosol to SL and the changes in distribution of calpastatin were also attenuated by treatment with calpain inhibitors. These results suggest that the depression in cardiac function and SL Na+/K+-ATPase activity in I/R hearts may be due to changes in the activity and translocation of calpain.
由于缺血再灌注（I/R）损伤导致的心脏功能障碍与氧化应激的发展和肌浆网（SL）Na+/K+-ATP 酶活性的降低有关。由于 I/R 和氧化应激都被报道会促进细胞内 Ca2+超载的发生，并激活钙蛋白酶等蛋白酶，因此本研究旨在探讨 I/R 心脏中钙蛋白酶的激活是否与 SL Na+/K+-ATP 酶活性及其同工型含量的变化有关。为此，用 2 种不同的钙蛋白酶抑制剂（亮肽素和 MDL28170）处理分离的大鼠心脏，然后进行 30min 缺血，再灌注 60min，并测量心脏功能、SL Na+/K+-ATP 酶活性、Na+/K+-ATP 同工型蛋白含量和钙蛋白酶活性。I/R 引起的心脏功能、Na+/K+-ATP 酶活性和 Na+/K+-ATP 同工型蛋白含量的降低与钙蛋白酶活性的增加有关，但用亮肽素处理心脏可预防这种降低。钙蛋白酶孵育 SL 膜会降低 Na+/K+-ATP 酶活性及其同工型的蛋白含量；亮肽素也能减弱这些变化。I/R 引起的心脏功能、SL Na+/K+-ATP 酶和钙蛋白酶活性的改变是 Ca2+依赖性的，可以通过 MDL28170（钙蛋白酶的特异性抑制剂）预防。钙蛋白酶同工型（I 和 II）从细胞质向 SL 的易位以及钙蛋白酶抑制素分布的变化也被钙蛋白酶抑制剂的处理所减弱。这些结果表明，I/R 心脏中心脏功能和 SL Na+/K+-ATP 酶活性的降低可能是由于钙蛋白酶活性和易位的改变所致。
