Ramsay R R, Dadgar J, Trevor A, Singer T P
Life Sci. 1986 Aug 18;39(7):581-8. doi: 10.1016/0024-3205(86)90037-8.
The oxidation of NAD+-linked substrates by rat brain mitochondria is completely inhibited by pre-incubation with 0.5 mM N-methyl-4-phenylpyridine (MPP+). The effect is dependent on the integrity of the mitochondria because far higher concentrations of MPP+ are required to inhibit NADH oxidation in inverted mitochondria or isolated inner membrane preparations. The reason for this difference in behavior has been traced to a novel system for the uptake of MPP+ into mitochondria against a concentration gradient. The uptake system is energized by the transmembrane potential, as shown by the fact that valinomycin plus K+, which collapses this gradient, abolishes MPP+ uptake, while agents which collapse the proton gradient have no effect on the process. If an uncoupler is added to mitochondria preloaded with MPP+, efflux of the latter occurs with the concentration gradient. The uptake system has been studied in liver, whole brain, cortex, and midbrain preparations from rats. It may be readily distinguished from the synaptic dopamine reuptake system, since the former is blocked by uncouplers and respiratory inhibitors, but not by dopamine or mazindol, whereas the synaptic system is blocked by mazindol and competitively inhibited by dopamine but is not affected by respiratory inhibitors or uncouplers. Energy-driven uptake of MPP+ by brain mitochondria may be a crucial step in the complex sequence of events leading to the neurotoxic actions of its precursor, MPTP.
大鼠脑线粒体对NAD⁺连接底物的氧化作用在与0.5 mM N-甲基-4-苯基吡啶（MPP⁺）预孵育后会被完全抑制。这种作用取决于线粒体的完整性，因为抑制倒置线粒体或分离的内膜制剂中的NADH氧化需要高得多浓度的MPP⁺。这种行为差异的原因已追溯到一种将MPP⁺逆浓度梯度摄取到线粒体中的新系统。摄取系统由跨膜电位提供能量，如下事实所示：缬氨霉素加钾离子会消除这种梯度，从而消除MPP⁺的摄取，而能消除质子梯度的试剂对该过程没有影响。如果将解偶联剂添加到预先加载有MPP⁺的线粒体中，MPP⁺会顺着浓度梯度流出。已经在大鼠的肝脏、全脑、皮层和中脑制剂中研究了摄取系统。它可以很容易地与突触多巴胺再摄取系统区分开来，因为前者被解偶联剂和呼吸抑制剂阻断，但不受多巴胺或吗茚酮的影响，而突触系统被吗茚酮阻断并被多巴胺竞争性抑制，但不受呼吸抑制剂或解偶联剂的影响。脑线粒体通过能量驱动摄取MPP⁺可能是导致其前体MPTP产生神经毒性作用的复杂事件序列中的关键一步。
