MELATONIN - ITS INTRACELLULAR AND GENOMIC ACTIONS

Besides its actions via membrane receptors on cells in specific areas of the brain and peripheral tissues, melatonin also has direct intrace llular actions. The neurohormone melatonin is a potent free radical sc avenger in vitro and a powerful antioxidant in vivo. Studies to date i ndicate that it is a better scavenger of the highly toxic hydroxyl and peroxyl radicals than some other known compounds. Melatonin also prev ents the toxicity of singlet oxygen and stimulates the antioxidative e nzyme, glutathione peroxidase. Considering its varied and potent antio xidant capability, it is possible that melatonin is an essential eleme nt of the antioxidant defense system of organisms. Besides these direc t intracellular actions of melatonin, it was recently discovered that the indole also has binding sites in the nucleus of many cells. Melato nin genomic actions are believed to follow its binding to these nuclea r loci.