Dickman K G, Mandel L J
Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710.
Am J Physiol. 1990 Jun;258(6 Pt 2):F1608-15. doi: 10.1152/ajprenal.1990.258.6.F1608.
The effects of inhibition of mitochondrial energy production at various points along the respiratory chain on glycolytic lactate production and transport function were examined in a suspension of purified rabbit renal proximal tubules. Paradoxically, partial blockage at site 3 by hypoxia (1% O2) induced lactate production, whereas total site 3 blockage by anoxia (0% O2) failed to stimulate glycolysis. Compared with anoxia, hypoxic tubules exhibited greater preservation of ATP and K+ contents during O2 deprivation and more fully recovered oxidative metabolism and transport function during reoxygenation. The mitochondrial site 1 inhibitor rotenone and the uncoupler carbonyl cyanide-p-trifluorome-thoxyphenylhydrazone (FCCP) were equipotent stimuli for lactate production, whereas the site 2 inhibitor antimycin A failed to stimulate glycolysis despite a 90% inhibition of O2 consumption. Compared with antimycin A, treatment with rotenone or FCCP resulted in less cell injury [measured by lactate dehydrogenase (LDH) release] and greater preservation of cell K+ and ATP contents. 2-Deoxyglucose blocked lactate production by 50% in the presence of rotenone and increased LDH release, suggesting that glycolytic ATP is partially protective. Addition of ouabain during rotenone treatment reduced lactate production by 50%, indicating that glycolytic ATP can be used to fuel the Na pump when mitochondrial ATP production is inhibited. We conclude that 1) proximal tubules can generate lactate during inhibition of oxidative metabolism by hypoxia, rotenone, or FCCP; 2) mitochondrial inhibition is not obligatorily linked to activation of glycolysis, since neither anoxia nor antimycin A stimulate lactate production; 3) when ATP can be produced through anaerobic glycolysis it serves to protect cell viability and transport function during respiratory inhibition.
在纯化的兔肾近端小管悬浮液中，研究了沿呼吸链不同位点抑制线粒体能量产生对糖酵解乳酸生成和转运功能的影响。矛盾的是，低氧（1% O₂）在位点3处的部分阻断诱导了乳酸生成，而缺氧（0% O₂）在位点3处的完全阻断未能刺激糖酵解。与缺氧相比，低氧小管在缺氧期间表现出对ATP和K⁺含量的更好保存，并且在复氧期间更完全地恢复了氧化代谢和转运功能。线粒体位点1抑制剂鱼藤酮和解偶联剂羰基氰-对-三氟甲氧基苯腙（FCCP）是乳酸生成的等效刺激物，而位点2抑制剂抗霉素A尽管抑制了90%的氧气消耗，但未能刺激糖酵解。与抗霉素A相比，用鱼藤酮或FCCP处理导致细胞损伤更小[通过乳酸脱氢酶（LDH）释放来衡量]，并且细胞K⁺和ATP含量的保存更好。在鱼藤酮存在的情况下，2-脱氧葡萄糖使乳酸生成减少了50%，并增加了LDH释放，这表明糖酵解产生的ATP具有部分保护作用。在鱼藤酮处理期间添加哇巴因使乳酸生成减少了50%，表明当线粒体ATP生成受到抑制时，糖酵解产生的ATP可用于为钠泵提供能量。我们得出以下结论：1）近端小管在低氧、鱼藤酮或FCCP抑制氧化代谢期间可产生乳酸；2）线粒体抑制并非必然与糖酵解的激活相关，因为缺氧和抗霉素A均未刺激乳酸生成；3）当通过无氧糖酵解能够产生ATP时，它有助于在呼吸抑制期间保护细胞活力和转运功能。
