HIGH MELATONIN SOLUBILITY IN AQUEOUS-MEDIUM

The pineal hormone melatonin (5-methoxy-N-acetyltryptamine) has been r eported to participate in important physiological processes. Although some of its biological actions seem to depend on a protein receptor at the membrane surface, melatonin is known to interact with a large var iety of tissues and cells, suggesting that the molecule may not necess arily interact through a specific membrane receptor at a specific cell . Most discussions of melatonin activity have assumed that the molecul e is highly hydrophobic. Contrary to belief, the present work shows th at melatonin is soluble in a purely aqueous medium up to 5 x 10(-3) M and describes a new method of melatonin preparation which shows the hi gh hydrophilicity of the molecule. The results presented will affect t he current biological hypothesis on the need of a melatonin carrier in the blood stream or the mechanisms which allow the hormone to cross t he cell membrane and interact at the level of the nucleus.