Bolli R, Jeroudi M O, Patel B S, DuBose C M, Lai E K, Roberts R, McCay P B
Department of Medicine, Baylor College of Medicine, Houston, TX 77030.
Proc Natl Acad Sci U S A. 1989 Jun;86(12):4695-9. doi: 10.1073/pnas.86.12.4695.
Electron paramagnetic resonance (EPR) spectroscopy was used to investigate whether (i) the free radicals produced in the "stunned" myocardium (myocardium with postischemic contractile dysfunction) are derived from O2, (ii) inhibition of radical reactions improves function, and (iii) i.v. spin traps are effective. Open-chest dogs undergoing a 15-min coronary occlusion received an i.v. infusion of the spin trap, alpha-phenyl N-tert-butylnitrone (PBN) (50 mg/kg). In group I (n = 6), EPR signals characteristic of radical adducts of PBN appeared in the coronary venous blood during ischemia and increased dramatically after reperfusion. In group II (n = 6), which received PBN and i.v. superoxide dismutase (SOD; 16,000 units/kg) plus catalase (12,000 units/kg), myocardial production of PBN adducts was undetectable during ischemia (delta = -100%, P less than 0.01 vs. group I) and markedly inhibited after reperfusion (delta = -86%, P less than 0.001). This effect was seen at all levels of ischemic zone flow but was relatively greater in the low-flow range. In group III (n = 8), the same dosages of SOD and catalase without PBN markedly enhanced contractile recovery (measured as systolic wall thickening) after reperfusion [P less than 0.01 at 3 hr vs. controls (group IV, n = 7)]. Systemic plasma activity of SOD and catalase averaged 127 +/- 24 and 123 +/- 82 units/ml, respectively, 2 min after reperfusion. PBN produced no apparent adverse effects and actually improved postischemic contractile recovery in group I (P less than 0.05 at 3 hr vs. controls). This study shows that (i) SOD and catalase are highly effective in blocking free radical reactions in vivo, (ii) the radicals generated in the "stunned" myocardium are derived from univalent reduction of O2, and (iii) inhibition of radical reactions improves functional recovery. The results provide direct, in vivo evidence to support the hypothesis that reactive oxygen metabolites play a causal role in the myocardial "stunning" seen after brief ischemia.
采用电子顺磁共振（EPR）光谱法研究：（i）“顿抑”心肌（具有缺血后收缩功能障碍的心肌）中产生的自由基是否源自O2；（ii）自由基反应的抑制是否能改善功能；以及（iii）静脉注射自旋捕捉剂是否有效。对开胸犬进行15分钟的冠状动脉闭塞，并静脉输注自旋捕捉剂α-苯基N-叔丁基硝酮（PBN，50mg/kg）。在I组（n = 6）中，缺血期间冠状动脉静脉血中出现了PBN自由基加合物的特征性EPR信号，再灌注后显著增加。在II组（n = 6）中，给予PBN以及静脉注射超氧化物歧化酶（SOD，16000单位/kg）加过氧化氢酶（12000单位/kg），缺血期间未检测到心肌产生PBN加合物（Δ = -100%，与I组相比P < 0.01），再灌注后显著受抑制（Δ = -86%，P < 0.001）。在缺血区血流的所有水平均可见此效应，但在低血流范围内相对更明显。在III组（n = 8）中，给予相同剂量的SOD和过氧化氢酶但未给予PBN，再灌注后收缩功能恢复（以收缩期室壁增厚衡量）显著增强[与对照组（IV组，n = 7）相比，3小时时P < 0.01]。再灌注2分钟后，全身血浆中SOD和过氧化氢酶活性平均分别为127±24和123±82单位/ml。PBN未产生明显不良反应，实际上还改善了I组缺血后的收缩功能恢复（与对照组相比，3小时时P < 0.05）。本研究表明：（i）SOD和过氧化氢酶在体内阻断自由基反应非常有效；（ii）“顿抑”心肌中产生的自由基源自O2的单价还原；以及（iii）自由基反应的抑制可改善功能恢复。这些结果提供了直接的体内证据，支持活性氧代谢产物在短暂缺血后出现的心肌“顿抑”中起因果作用这一假说。
