| 1: Indian J Exp Biol. 1996 May;34(5):391-402.
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Melatonin: a master hormone and a candidate for universal
panacea.
Kumar V.
Department of Zoology, University of Lucknow, India.
The molecule of melatonin seems to have been evolutionarily conserved. Its
presence has been demonstrated in almost all groups of organisms, from plants,
protozoa to people. During evolution, melatonin is claimed to have mediated
dark adaptation. The universal presence of melatonin may be because it is
lipophilic in nature which enables it to cross all biological (lipid membrane)
barriers and to diffuse into every compartment of the cell, and because it
serves as an antioxidant and is used as a free radical scavenger. In
vertebrates, the pineal gland is the single largest source of melatonin
production although, especially in non-mammalian vertebrates, other organs
(e.g. retina, harderian gland etc.) may contribute significantly to the blood
melatonin levels. In invertebrates, on the other hand, the pineal gland is
absent and, therefore, melatonin secretion is clearly derived from another
source(s). Regardless of the site of synthesis and the nature of organisms (diurnal,
nocturnal or crepuscular), melatonin is secreted in the night and melatonin
biosynthetic pathway remains essentially the same. Tryptophan, an amino acid
derived from dietary sources, undergoes a series of enzymatic reactions to
produce melatonin. The rhythm in melatonin secretion is generated endogenously
by the circadian pacemaker(s) in the suprachiasmatic nuclei (SCN), and
regulated by environmental light:dark cycle. Melatonin through its action on
the SCN synchronizes disrupted or free-running circadian rhythms, and
regulates a variety of daily and seasonal changes in the physiology and
behaviour of animals. Emerging scientific evidence for the role of melatonin
as therapeutic agent in the treatment of circadian rhythm-associated sleep
disorders in persons having normal social working hours and shift workers, in
jet lag, in immunological functions etc. have considerably increased interest
in this hormone molecule. The role of melatonin in organisms physiology has
now been widely recognized, and the wealth of information accumulated in the
past two decades indicate it to be the best hormone candidate to be
investigated for a universal panacea.
Publication Types:
PMID: 9063071 [PubMed - indexed for MEDLINE]