中文摘要：

钙网蛋白（calreticulin，CRT）和caspase-12是重要的内质网（endoplasmic reticulum，ER）应激分子，本实验在心肌细胞低氧／复氧（hypoxia／reoxygenation，H／R）模型上观察低氧预处理（hypoxic preconditioning，HPC）对CRT和caspase-12表达及活化的影响，探讨内质网应激（endoplasmic reticulum stress，ERS）在HPC保护机制中的意义及其细胞信号转导机制。原代培养的Sprague-Dawley乳鼠心肌细胞随机分为6组：H／R组、HPC＋H／R组、SB203580＋HPC＋H／R组、SP600125＋HPC＋H／R组、HPC组和对照组。以细胞存活率、乳酸脱氢酶（lactate dehydrogenase，LDH）活性及流式细胞术检测细胞损伤情况：Western blot方法检测CRT和caspase-12表达、活化及p38丝裂素活化蛋白激酶（mitogen—activated protein kinases，MAPK）、cJun N-terminal kinase（JNK）磷酸化水平。结果表明：（1）HPC具有细胞保护作用，与H／R组比较，HPC＋H／R组细胞凋亡率和LDH漏出分别降低6．6％和70．0％，存活率增高6．4％：HPC前以特异性p38MAPK抑制剂SB203580预孵育消除HPC的保护作用，与HPC＋H／R组相比，细胞凋亡率和LDH漏出分别增高5．4％和2．1倍，存活率降低5．4％，JNK特异性抑制剂SP600125预孵育对HPC的保护作用无明显影响。（2）H／R明显上调CRT表达（较对照组高8．1倍）和caspase-12活性（较对照组高33．2倍）；单独HPC可诱导CRT表达增多（较对照组高2．6倍），但上调程度较H／R组低60％。H／R前进行HPC降低CRT过表达程度（降低72．4％）及caspase-12活化水平（降低59．6％）。（3）HPC前应用p38MAPK抑制剂，抑制CRT表达上调（分别较HPC＋H／R组和HPC组低63．9％和71．9％），并消除HPC减轻H／R上调caspase-12活性的作用（较HPC＋H／R组高7．1倍）；HPC前抑制JNK活性对CRT、caspase-12表达和活化均无明显影响。上述结果提示：HPC可激发适当的ERS，抑制H／R诱导的过度ERS，?

英文摘要：

Calreticulin （CRT）, an important Ca^2＋-binding molecular chaperone in the endoplasmic reticulum （ER）, and caspase- 12, a pivotal molecule mediating ER-initiated apoptosis, are involved in the ER stress （ERS）. Using primary cultured neonatal cardiomyocytes, CRT and caspase-12 expression and activation during hypoxic preconditioning （HPC） and hypoxia/reoxygenation （H/R） were studied to explore the role of ERS in cardioprotection by HPC. And by using SB203580 and SP600125 [the specific inhibitors of p38 mitogenactivated protein kinase （MAPK） and c-Jun N-terminal kinase （JNK） ] separately, the role of p38 MAPK in HPC-induced ERS was also detected. Neonatal cardiomyocytes were prepared from Sprague-Dawley rats aged 24 h, and cultured in DMEM medium containing 10% fetal bovine serum, and then randomly divided into six groups as follows： H/R, HPC＋H/R, SB203580＋HPC＋H/R,SP600125＋HPC＋H/R, HPC and control groups. H/R was produced by 2-hour hypoxia/14-hour reoxygenation, and HPC by 20-minute hypoxia/24-hour reoxygenation. Morphological studies, estimation of lactate dehydrogenase （LDH） leakage and flow cytometry were employed to assess cell apoptosis and necrosis. CRT and caspase-12 expression and activation, levels of phospho-p38 MAPK and phospho-JNK were detected by Western blot. All experiments were repeated at least four separate times. The results obtained are as follows： （1） HPC relieved the cell injury caused by H/R. Compared with that in H/R group, cells＇ survival rate in HPC＋H/R group increased by 6.4%, and the apoptosis rate and LDH leakage in the cell culture medium decreased by 6.6% and 70.0%, respectively. （2） H/R induced caspase-12 activation （33.2-fold increase in comparison with control） and CRT expression （8.1-fold increase in comparison with control）. HPC itself resulted in mild CRT up-regulation （2.6-fold increase in comparison with control）, but the extent of up-regulation was lower than that induced by H/R. HPC before H/R was found t