A therapeutic method is provided comprising treating a mammal subject to hypoxia with an amount of 2(R,S)-D-ribo-(1′,2′,3′,4′-tetrahydroxybutyl)thiazolidine-4(R)-carboxylic acid (RibCys) or a pharmaceutically acceptable salt thereof effective to both maintain, restore or increase both the ATP levels and the glutathione (GSH) levels in said tissue.