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Neurally-mediated and neurally-independent beneficial actions of melatonin in the gastrointestinal tract

100%

Reiter R. J., Tan D-X., Mayo J. C., Sainz R. M., Leon J., Bandyopadhyay D.

Journal of Physiology and Pharmacology. Supplement

2003

tom 54

nr 4

113-125

Melatonin (N-acetyl-5-methoxytryptamine), originally discovered in the pineal gland, is now known also to be present in the gastrointestinal tract from the stomach to the colon. It is localized and likely synthesized in the enterochromaffin cells of the mucosal lining. Its functions in the gut generally seem to be protective of the mucosa from erosion and ulcer formation and to possibly influence movement of the gastrointestinal contents through the digestive system. In this brief review, we summarize the work documenting the function of melatonin in influencing bicarbonate secretion in the stomach and its role in preventing and repairing ulcers in the stomach and duodenum. Melatonin’s actions in the control of bicarbonate secretion involve the central and peripheral sympathetic nervous systems and the actions are receptor mediated. Conversely, melatonin’s actions in reducing ulcer formation also seemingly involve the ability of the indole to directly scavenge toxic oxygen-based reactants, e.g., the hydroxyl radical, and possibly to promote antioxidative enzyme activities. These same processes may be involved in the mechanisms by which melatonin promotes ulcer healing. Additionally, however, melatonin’s effects on the healing of ulcers includes actions of blood flow in the margins of the ulcer and also on the sensory nerves. All indications are that melatonin has a variety of beneficial effects in the gastrointestinal tract. It is likely, however, that additional actions of melatonin on the digestive system will be uncovered.

Melatonin as an antioxidant: biochemical mechanisms and pathophysiological implications in humans

100%

Reiter R. J., Tan D., Mayo J. C., Sainz R. M., Leon J., Czarnocki Z.

Acta Biochimica Polonica

2003

tom 50

nr 4

This brief resume enumerates the multiple actions of melatonin as an antioxidant. This indoleamine is produced in the vertebrate pineal gland, the retina and possibly some other organs. Additionally, however, it is found in invertebrates, bacteria, unicellular organisms as well as in plants, all of which do not have a pineal gland. Melatonin's functions as an antioxidant include: a), direct free radical scavenging, b), stimulation of antioxidative enzymes, c), increasing the efficiency of mitochondrial oxidative phosphorylation and reducing electron leakage (thereby lowering free radical generation), and 3), augmenting the efficiency of other antioxidants. There may be other functions of melatonin, yet undiscovered, which enhance its ability to protect against molecular damage by oxygen and nitrogen-based toxic reac- tants. Numerous in vitro and in vivo studies have documented the ability of both physiological and pharmacological concentrations to melatonin to protect against free radical destruction. Furthermore, clinical tests utilizing melatonin have proven highly successful; because of the positive outcomes of these studies, melatonin's use in disease states and processes where free radical damage is involved should be increased.

Ograniczanie wyników

1 Acta Biochimica Polonica

1 Journal of Physiology and Pharmacology. Supplement

2 Leon J.

2 Mayo J. C.

2 Reiter R. J.

2 Sainz R. M.

1 Bandyopadhyay D.

1 Czarnocki Z.

1 Tan D-X.

1 Tan D.

2 2003

Wyniki wyszukiwania

Neurally-mediated and neurally-independent beneficial actions of melatonin in the gastrointestinal tract

Melatonin as an antioxidant: biochemical mechanisms and pathophysiological implications in humans