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Melatonin metabolism

Ursing C, Wikner J, Brismar K, Rqjdmark S. Caffeine raises the serum melatonin level in healthy subjects an indication of melatonin metabolism by c3 chrome P450 (C YP) 1A2. J Endocrinol Invest (2003) 26, 403-6. [Pg.1265]

Circulating melatonin is metabolized mainly in the liver, where it is first hydroxylated in the C6-position by cytochrome P450 monooxygenases (isoenzymes... [Pg.286]

Melatonin can be metabolized non-enzymatically in all cells, and extra-cellularly by free radicals and a few other oxidants. It is converted into cyclic 3-hydroxymelatonin when it directly scavenges two hydroxyl radicals (Tan et al. 1998). In the brain, a substantial fraction of melatonin is metabolized to kynuramine derivatives (Hirata et al. 1974). AFMK is produced by numerous non-enzymatic and enzymatic mechanisms (Hardeland et al. 2006) its formation by myeloperoxidase appears to be important in quantitative terms (Ferry et al. 2005). [Pg.287]

Phase-shifting by melatonin is attributed to its action at MT2 receptors present in the SCN (Liu et al. 1997). The chronobiological effect of melatonin is due to its direct influence on the electrical and metabolic activity of the SCN, a finding that has been confirmed both in vivo and in vitro. The application of melatonin directly to the SCN significantly increases the amplitude of the melatonin peak, thereby suggesting that in addition to its phase-shifting effect melatonin directly acts on the amplitude of the oscillations (Pevet et al. 2002). However, this amplitude modulation seems to be unrelated to clock gene expression in the SCN (Poirel et al. 2003). [Pg.293]

Melatonin might be an indirect in vivo antioxidant, getting metabolized into a genuine free radical scavenger in some enzymatic processes. [Pg.890]

Ma X, Idle JR, Krausz KW, Gonzalez FJ. 2005. Metabolism of melatonin by human cytochromes P450. Drug Metab... [Pg.86]

HT is metabolized by the action of monoamine oxidase by a process of oxidative deamination to yield 5-hydroxyindoleacetic acid (5-HIAA). In the pineal gland, 5-HT is o-methylated to form melatonin. While the physiological importance of this transmitter in the regulation of the oestrus cycle in ferrets would appear to be established, its precise role in man is unknown. Nevertheless, it has been speculated that melatonin plays some... [Pg.71]

Trp metabolism is complex and leads to multiple products, including serotonin, melatonin, and NAD. ... [Pg.128]

Melatonin is promoted commercially as a sleep aid by the food supplement industry (see Chapter 64). Ramelteon is a selective MTi and MT2 agonist that is approved for the medical treatment of insomnia. This drug has no addiction liability (it is not a controlled substance), and it appears to be distinctly more efficacious than melatonin (but less efficacious than benzodiazepines) as a hypnotic. It is metabolized by P450 enzymes and should not be used in individuals taking CYP1A2 inhibitors. It has a half-life of... [Pg.358]

Barrenetxe J, Delagrange P, Martinez JA Physiologic and metabolic functions of melatonin. J Physiol Biochem 2004 60 61. [PMID 15352385]... [Pg.371]

Doses of melatonin as low as 3 mg (if given during the day) can produce increases in blood levels of melatonin that are 50 times higher than normal levels. Thus, megadose pills offered by some health food stores may cause melatonin concentrations that are vastly in excess of what is needed to affect sleep or biological rhythms. Melatonin is metabolized by the liver fairly quickly, so that half of the ingested melatonin is eliminated from the body within an hour of taking it, and an entire 3 mg dose is eliminated in 6 to 10 hours. [Pg.60]

Tryptophan is a metabolic precursor for many important biochemical compounds, such as nicotinic acid, kynurenic acid, serotonin, and melatonin (67). The tryptophan content of various food-... [Pg.66]

Melatonin (lV-acetyl-5-methoxytryptamine) is a neuro-hormone secreted by the pineal gland from the amino acid precursor [,-tryptophan. Its endogenous secretion is photosensitive and has a circadian rhythm—plasma melatonin concentrations are highest at night in both diurnal and nocturnal animals, and fall with age (1). The nocturnal melatonin peak coincides with a drop in body temperature and increased sleepiness in healthy humans. Oral melatonin has a short half-life (30-50 minutes) and extensive first-pass metabolism. Its clearance is reduced in severe liver disease (2). [Pg.495]

Lane EA, Moss HB. Pharmacokinetics of melatonin in man first pass hepatic metabolism. J Clin Endocrinol Metab 1985 61(6) 1214-6. [Pg.498]

Nishida S. Metabolic effects of melatonin on oxidative stress and diabetes mellitus. Endocrine. 2005 27 131-136. [Pg.617]

Experts are not sure how melatonin influences the development of cancer. A recent study published in 1999 in Cancer Research suggests that melatonin may help to starve cancer cells. Tumors use a type of fat called linoleic acid as a food source. Melatonin prevented the tumor cells in rats from being able to metabolize linoleic, but only when it was given to rats during the late afternoon. When it was given to the rats earlier in the day it did not have any effect. [Pg.303]

Have a history of liver disease. Melatonin is metabolized in the liver. Melatonin may remain within the body for a longer time and in larger amounts if the liver is not able to break down this hormone so that it can be excreted. [Pg.304]


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See also in sourсe #XX -- [ Pg.107 ]




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