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

Abstract

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.