Zuo Li, Pasniciuc Silviu, Wright Valerie P, Merola A John, Clanton Thomas L
The Ohio State University Medical Centre, Department of Internal Medicine, Dorothy M. Davis Heart & Lung Research Institute, Division of Pulmonary and Critical Care Medicine, Columbus, OH 43210, USA.
Antioxid Redox Signal. 2003 Oct;5(5):667-75. doi: 10.1089/152308603770310347.
Isolated diaphragm releases low levels of superoxide (O2*-) at rest and much higher levels during heat stress. The molecular source is unknown. The hypothesis was tested that heat stress stimulates mitochondrial complex activity or NADPH oxidases, resulting in increased O2*- release. The mitochondria within intact rat diaphragm were inhibited at complex I (amobarbital or rotenone) or complex I and II (rotenone plus thenoyltrifluoroacetone). NADPH oxidases were blocked by diphenyliodonium. None of these treatments inhibited O2*- release. Conversely, most blockers stimulated O2*- release. As intracellular O2*- generators require a mechanism for O2*- transport across the membrane, anion channel blockers, probenecid and 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid, were also tested. Neither blocker had any inhibitory effect on O2*- release. These results suggest that O2*- released from diaphragm is not directly dependent on mitochondrial complex activity and that it is not a reflection of passive diffusion of O2*- through anion channels. Although the molecular source for extracellular O2*- remains elusive, it is clearly sensitive to temperature and conditions of "chemical hypoxia" induced by partial or complete mitochondrial inhibition.
离体膈肌在静息状态下释放低水平的超氧阴离子（O2*-），在热应激期间释放水平则高得多。其分子来源尚不清楚。我们检验了这样一个假说：热应激会刺激线粒体复合物活性或NADPH氧化酶，从而导致O2*-释放增加。完整大鼠膈肌内的线粒体在复合物I（异戊巴比妥或鱼藤酮）或复合物I和II（鱼藤酮加噻吩甲酰三氟丙酮）处受到抑制。NADPH氧化酶被二苯基碘鎓阻断。这些处理均未抑制O2*-释放。相反，大多数阻断剂刺激了O2*-释放。由于细胞内O2*-生成器需要一种O2*-跨膜转运机制，因此还测试了阴离子通道阻断剂丙磺舒和4,4'-二异硫氰酸根合芪-2,2'-二磺酸。两种阻断剂对O2*-释放均无抑制作用。这些结果表明，膈肌释放的O2*-并不直接依赖于线粒体复合物活性，也不是O2*-通过阴离子通道被动扩散的反映。尽管细胞外O2*-的分子来源仍然难以捉摸，但它显然对温度和由部分或完全线粒体抑制引起的“化学性缺氧”条件敏感。
