MELATONIN STIMULATES BRAIN GLUTATHIONE-PEROXIDASE ACTIVITY

Exogenously administered melatonin causes a 2-fold rise in glutathione peroxidase activity within 30 min in the brain of the rat. Furthermor e, brain glutathione peroxidase activity is higher at night than durin g the day and is correlated with high night-time tissue melatonin leve ls. Glutathione peroxidase is thought to be the principal enzyme elimi nating peroxides in the brain. This antioxidative enzyme reduces the f ormation of hydroxyl hydroxyl radicals formed via iron-catalyzed Fento n-type reactions from hydrogen peroxide by reducing this oxidant to wa ter. Since the hydroxyl radical is the most noxious oxygen radical kno wn, induction of brain glutathione peroxidase might be an important me chanism by which melatonin exerts its potent neuroprotective effects.