Rowland R T, Meng X, Cleveland J C, Meldrum D R, Harken A H, Brown J M
Department of Surgery, University of Colorado Health Sciences Center, 4200 East Ninth Avenue (C305), Denver, Colorado 80262, USA.
J Surg Res. 1997 Aug;71(2):155-60. doi: 10.1006/jsre.1997.5142.
Repetitive episodes of brief ischemia induce myocardial adaptation to prolonged ischemia. To investigate whether this myocardial adaptive response involves gene transcription and de novo protein synthesis, this study examined the effects of actinomycin D (ActD) and cycloheximide (Chx) on the cardioprotection induced by repeated ischemic preconditioning. Isolated, perfused working rat hearts underwent cyclic ischemia (CI, four 5-min ischemic intervals, 37 degrees C) with and without pretreatment with Chx (1.0 mg/kg, ip; translation inhibition) or ActD (1.5 mg/kg, ip; transcription inhibition) 3 hr prior to heart isolation. All hearts were subjected to 20 min global ischemia (37 degrees C) and 40 min reperfusion (I/R). Coronary effluent was assayed for creatine kinase (CK) activity. Myocardial tissue was homogenized and crude protein content determined. CI preconditioning improved postischemic recovery of cardiac output (CO; 48 +/- 5.1% vs 73 +/- 2.8% for control and CI, respectively, P < 0.05) and reduced CK release (61 +/- 8.5 U/L vs 38 +/- 4.2 U/L for control and CI, respectively, P < 0.05). The beneficial effects of CI preconditioning on myocardial function and cellular integrity were abolished by Chx while ActD had no effect. Myocardial protein content was increased in CI preconditioned myocardium relative to control hearts (5082 +/- 89 microg/g vs. 4459 +/- 260 microg/g, respectively, P < 0.05). Similarly, pretreatment with Chx but not ActD prevented the increase in myocardial protein content (Chx + CI, 4020 +/- 254 microg/g; ActD + CI, 5049 +/- 68 microg/g, P < 0.05 Chx + CI vs CI or ActD + CI). Myocardial dry/wet weight ratios were not different between groups (P > 0.05). We conclude that CI preconditioning induces protein synthesis-dependent myocardial protection against I/R injuries. CI-induced de novo protein synthesis in the myocardium appears to be regulated at the translational level rather than by gene transcription.
短暂缺血的重复发作可诱导心肌适应延长的缺血。为研究这种心肌适应性反应是否涉及基因转录和从头合成蛋白质，本研究检测了放线菌素D（ActD）和环己酰亚胺（Chx）对重复缺血预处理诱导的心脏保护作用的影响。在心脏分离前3小时，对离体灌注的工作大鼠心脏进行循环缺血（CI，四个5分钟缺血间期，37℃），同时或不进行Chx（1.0mg/kg，腹腔注射；翻译抑制）或ActD（1.5mg/kg，腹腔注射；转录抑制）预处理。所有心脏均经历20分钟全心缺血（37℃）和40分钟再灌注（I/R）。检测冠状动脉流出液中的肌酸激酶（CK）活性。将心肌组织匀浆并测定粗蛋白含量。CI预处理改善了缺血后心输出量（CO）的恢复（对照组和CI组分别为48±5.1%和73±2.8%，P<0.05），并减少了CK释放（对照组和CI组分别为61±8.5U/L和38±4.2U/L，P<0.05）。Chx消除了CI预处理对心肌功能和细胞完整性的有益作用，而ActD则无影响。与对照心脏相比，CI预处理心肌中的心肌蛋白含量增加（分别为5082±89μg/g和4459±260μg/g，P<0.05）。同样，Chx预处理而非ActD预处理可阻止心肌蛋白含量的增加（Chx+CI，4020±254μg/g；ActD+CI，5049±68μg/g，Chx+CI与CI或ActD+CI相比，P<0.05）。各组间心肌干/湿重比无差异（P>0.05）。我们得出结论，CI预处理可诱导依赖蛋白质合成的心肌对I/R损伤的保护作用。CI诱导的心肌从头合成蛋白质似乎在翻译水平而非基因转录水平受到调控。
