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