Membrane potential generation coupled to oxidation of external NADH in liver mitochondria

FEBS Letters

Bodrova, M.E.¹  Dedukhova, V.I.¹  Skulachev, V.P.¹  Mokhova, E.N.¹ 

[1]Department of Bioenergetics, A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia

关键词: Exogenous NADH;    Cytochrome c;    Membrane potential;    Liver mitochondrion;    Apoptosis;    Superoxide;    ΔΨ;    transmembrane electric potential difference;    BSA;    bovine serum albumin;    DNP;    2;    4-p-dinitrophenol;    ROS;    reactive oxygen species;    TMPD;    N;    N;    N′;    N′-tetramethyl p-phenylene diamine;    TPP+;    tetraphenylphosphonium;   

DOI  :  10.1016/S0014-5793(98)01072-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Oxidation of added NADH by rat liver mitochondria has been studied. It is found that exogenous NADH, when oxidized by rat liver mitochondria in sucrose hypotonic medium supplemented with Mg²⁺ and EGTA, generates a membrane potential (ΔΨ) even in the absence of added cytochrome c. ADP and phosphate decrease ΔΨ, the effect being reversed by oligomycin. Rotenone and myxothiazol do not inhibit ΔΨ generated by oxidation of exogenous NADH. Added cytochrome c increases the rate of the exogenous NADH oxidation and coupled ΔΨ formation. In sucrose isotonic medium, or in hypotonic medium without Mg²⁺, exogenous NADH fails to stimulate respiration and to form a membrane potential. In the presence of Mg²⁺, exogenous NADH appears to be effective in ΔΨ generation in isotonic sucrose medium if mitochondria were treated with digitonin. In isotonic KCl without Mg²⁺, oxidation of exogenous NADH is coupled to the ΔΨ formation and MgCl₂ addition before mitochondria prevents this effect. In hypotonic (but not in isotonic) sucrose medium, Mg²⁺ makes a portion of the cytochrome c pool reducible by exogenous NADH or ascorbate. It is assumed that (i) hypotonic treatment or digitonin causes disruption of the outer mitochondrial membrane, and, as a consequence, desorption of the membrane-bound cytochrome c in a Mg²⁺-dependent fashion; (ii) incubation in isotonic KCl without Mg²⁺ results in swelling of mitochondrial matrix, disruption of the outer membrane and cytochrome c desorption whereas Mg²⁺ lowers the K⁺ permeability of the inner membrane and, hence, prevents swelling; (iii) desorbed cytochrome c is reduced by added NADH via NADH-cytochrome b ₅ reductase and cytochrome b ₅ or by ascorbate and is oxidized by cytochrome oxidase. The role of desorbed cytochrome c in oxidation of superoxide and cytoplasmic NADH as well as possible relations of these events to apoptosis are discussed.

【 授权许可】

Unknown