Menadione (2-methyl-1,4-naphthoquinone)-induced Ca2+ release from rat-liver mitochondria is caused by NAD(P)H oxidation.

Incubation of rat-liver mitochondria with menadione in the presence of succinate and rotenone resulted in rapid glutathione and NAD(P)H oxidation followed by Ca2+ release and mitochondrial swelling. Ca2+ release, NAD(P)H oxidation and mitochondrial swelling, were also observed in mitochondria from selenium-deficient rats. Glutathione was only slowly oxidized, suggesting that glutathione oxidation, and subsequent NAD(P)H oxidation via the glutathione peroxidase-glutathione reductase system were not required for Ca2+ release by menadione. Isocitrate prevented and reversed Ca2+ release dose-dependently but dicoumarol had no effect indicating that NADH-ubiquinone oxidoreductase and not DT-diaphorase was responsible for NAD(P)H oxidation. Superoxide anion radical was formed by cyanide-resistant respiration, suggesting that menadione undergoes a one-electron reduction to an autoxidizable semiquinone radical by NADH-ubiquinone oxidoreductase. The inability of menadione to oxidize glutathione in selenium-deficient mitochondria indicates that the metabolism of the superoxide dismutation product, H2O2, by glutathione peroxidase was probably responsible for the glutathione oxidation in selenium-replete mitochondria.