Effect of dicumarol, a Nad(P)h: quinone acceptor oxidoreductase 1 (DT-diaphorase) inhibitor on ubiquinone redox cycling in cultured rat hepatocytes.

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Kishi T, Takahashi T, Mizobuchi S, Mori K, Okamoto T

Effect of dicumarol, a Nad(P)h: quinone acceptor oxidoreductase 1 (DT-diaphorase) inhibitor on ubiquinone redox cycling in cultured rat hepatocytes.

Free Radic Res. 2002 Apr;36(4):413-9.

PubMed ID

12069105 [ View in PubMed

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Abstract

Ubiquinol is considered to serve as an endogenous antioxidant. However, the mechanism by which the redox state of intracellular ubiquinone (UQ) is maintained is not well established. The effect of dicumarol, an inhibitor of NAD(P)H: quinone acceptor oxidoreductase 1 (NQO1 = DT-diaphorase, EC 1.6.99.2), on the reduction of UQ in cultured rat hepatocytes was investigated in order to clarify whether or not NQO1 is involved in reducing intracellular UQ. A concentration of 5 microM dicumarol, which does not inhibit cytosolic NADPH-dependent UQ reductase in vitro, was observed to almost completely inhibit NQO1 and thereby to stimulate cytotoxicity of 2-methyl-1,4-naphthoquinone (menadione) in cultured rat hepatocytes. However, 5 microM dicumarol did not inhibit reduction of endogenous UQ-9, as well as exogenous UQ-10 added to the hepatocytes. In addition, it did not stimulate the formation of thiobarbituric acid reactive substances (TBARS) in the hepatocytes. These results suggested that NQO1 is not involved in maintaining UQ in the reduced state in the intact liver cells.

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Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Menadione	NAD(P)H dehydrogenase [quinone] 1	Protein	Humans	Unknown	Not Available	Details