Role of mitochondrial lactate dehydrogenase and lactate oxidation in the intracellular lactate shuttle
Role of mitochondrial lactate dehydrogenase and lactate oxidation in the intracellular lactate shuttle
复制标题
DOI：
10.1073/pnas.96.3.1129
复制
发表时间：
1999-02-02
影响因子：
11.1
通讯作者：
Butz, CE
中科院分区：
文献类型：
--
作者：
Brooks, GA;Dubouchaud, H;Butz, CE
为了评估线粒体乳酸脱氢酶（LDH）在体内组织乳酸清除和氧化中的潜在作用，将分离的大鼠肝脏、心脏和骨骼肌线粒体与乳酸、丙酮酸、谷氨酸和琥珀酸盐孵育。此外，还使用了α -氰基-4-羟基肉桂酸（CINN），一种已知的单羧酸盐转运抑制剂和草酸酯，一种已知的LDH抑制剂。线粒体容易氧化丙酮酸和乳酸，具有相似的状态3和4呼吸速率，呼吸控制（状态3/状态4）和ADP/O比率。以乳酸或丙酮酸为底物时，α -氰基-4-羟基肉桂酸阻断对添加ADP的呼吸反应，但该阻断被添加谷氨酸（络合物i -连接）和琥珀酸（络合物ii -连接）底物所绕过。草酸酯增加了丙酮酸（约10-40%），但阻断了乳酸的氧化。凝胶电泳和电镜显示了LDH同工酶的分布模式，显示了组织特异性，但分离线粒体中的LDH同工酶模式与周围细胞区室中的LDH同工酶模式不同。在心脏中，LDH-1 （H4）集中在线粒体中，而LDH-5 （M4）同时存在于线粒体及其周围的细胞器和细胞器中。ldl -5在肝脏中占主导地位，但在线粒体中比在其他地方更丰富。由于乳酸盐浓度超过胞质丙酮酸浓度一个数量级，我们得出结论，乳酸盐是体内线粒体氧化的主要单羧酸盐。哺乳动物肝脏和横条肌线粒体可以氧化外源性乳酸，因为内部乳酸脱氢酶库促进乳酸氧化。
To evaluate the potential role of mitochondrial lactate dehydrogenase (LDH) in tissue lactate clearance and oxidation in vivo, isolated rat liver, cardiac, and skeletal muscle mitochondria were incubated with lactate, pyruvate, glutamate, and succinate. As well, alpha-cyano-4-hydroxycinnamate (CINN), a known monocarboxylate transport inhibitor, and oxamate, a known LDH inhibitor were used. Mitochondria readily oxidized pyruvate and lactate, with similar state 3 and 4 respiratory rates, respiratory control (state 3/state 4), and ADP/O ratios. With lactate or pyruvate as substrates, alpha-cyano-4-hydroxycinnamate blocked the respiratory response to added ADP, but the block was bypassed by addition of glutamate (complex I-linked) and succinate (complex II-linked) substrates. Oxamate increased pyruvate (approximate to 10-40%), but blocked lactate oxidation. Gel electrophoresis and electron microscopy indicated LDH isoenzyme distribution patterns to display tissue specificity, but the LDH isoenzyme patterns in isolated mitochondria were distinct from those in surrounding cell compartments. In heart, LDH-1 (H4) was concentrated in mitochondria whereas LDH-5 (M4) was present in both mitochondria and surrounding cytosol and organelles. LDH-5 predominated in liver but was more abundant in mitochondria than elsewhere. Because lactate exceeds cytosolic pyruvate concentration by an order of magnitude, we conclude that lactate is the predominant monocarboxylate oxidized by mitochondria in vivo. Mammalian liver and striated muscle mitochondria can oxidize exogenous lactate because of an internal LDH pool that facilitates lactate oxidation.