Melatonin Concentrations in the Gastrointestinal Tissues of Fetal Bovids

Bubenik, George A.; Brown, Gregory M.; Hacker, R. R.; Bartoš, Luděk

doi:10.2754/avb200069030177

Cited by 3 publications

(4 citation statements)

References 23 publications

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“…Using RIA, melatonin was detected in all segments of the GIT of cow fetuses in concentrations that exceed by several folds the levels found in the maternal blood [48]. Postnatally, melatonin was detected immunohistologically in several GI segments of 2-days-old rat pups [49].…”

Section: Ontogeny and Phylogenymentioning

confidence: 99%

Localization, Physiological Significance and Possible Clinical Implication of Gastrointestinal Melatonin

2001

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The gastrointestinal tract (GIT) is a major source of extrapineal melatonin. In some animals, tissue concentrations of melatonin in the GIT surpass blood levels by 10–100 times and the digestive tract contributes significantly to melatonin concentrations in the peripheral blood, particularly during the day. Some melatonin found in the GIT may originate from the pineal gland, as the organs of the digestive system contain binding sites, which in some species exhibit circadian variation. Unlike the production of pineal melatonin, which is under the photoperiodic control, release of GI melatonin seems to be related to periodicity of food intake. Melatonin and melatonin binding sites were localized in all GI tissues of mammalian and avian embryos. Postnatally, melatonin was localized in the GIT of newborn mice and rats. Phylogenetically, melatonin and melatonin binding sites were detected in GIT of numerous mammals, birds and lower vertebrates. Melatonin is probably produced in the serotonin-rich enterochromaffin cells (EC) of the GI mucosa and can be released into the portal vein postprandially. In addition, melatonin can act as an autocrine or a paracrine hormone affecting the function of GI epithelium, lymphatic tissues of the immune system and the smooth muscles of the digestive tube. Finally, melatonin may act as a luminal hormone, synchronizing the sequential digestive processes. Higher peripheral and tissue levels of melatonin were observed not only after food intake but also after a long-term food deprivation. Such melatonin release may have a direct effect on the various GI tissues but may also act indirectly via the CNS; such action might be mediated by sympathetic or parasympathetic nerves. Melatonin can protect GI mucosa from ulceration by its antioxidant action, stimulation of the immune system and by fostering microcirculation and epithelial regeneration. Melatonin may reduce the secretion of pepsin and the hydrochloric acid and influence the activity of the myoelectric complexes of the gut via its action in the CNS. Tissue or blood levels of melatonin may serve as a marker of GI lesions or tumors. Clinically, melatonin has a potential for a prevention or treatment of colorectal cancer, ulcerative colitis, irritable bowel syndrome, children colic and diarrhea.

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Section: Ontogeny and Phylogenymentioning

confidence: 99%

Localization, Physiological Significance and Possible Clinical Implication of Gastrointestinal Melatonin

2001

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“…Around the same time MT was further identified in rat retina, pineal, and Harderian gland by IMHC and radioimmunoassay (RIA) (4,28,29), Rat GIT MT showed no diurnal variation and no decrease following pinealectomy (30). GIT MT consistently shows higher levels than in the circulation (31)(32)(33) and total GIT MT content in the rat was calculated by Huether and coworkers as exceeding pineal content by some 400 times (34). Based on the foregoing it became readily apparent that GIT MT was not dependent on MT from the pineal and warrants the title "extrapineal".…”

Section: Extrapineal Mtmentioning

confidence: 99%

Low melatonin as a contributor to SARS-CoV-2 disease

Pandi‐Perumal¹,

Cardinali²,

Reíter³

et al. 2020

Melatonin Res.

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That the pineal gland is a source of melatonin is widely known; however, by comparison, few know of the much larger pool of extrapineal melatonin. That pool is widely distributed in all animals, including those that do not have a pineal gland, e.g., insects. Extrapineal melatonin is not released into the blood but is used locally to function as an antioxidant, anti-inflammatory agent, etc. A major site of action of peripherally-produced melatonin is the mitochondria where it neutralizes reactive oxygen species (ROS) that are generated during oxidative phosphorylation. Its role also includes major actions as an immune modulator reducing overreactions to foreign agents while simultaneously boosting immune processes. During a pandemic such as coronavirus disease 2019 (COVID-19), caused by the virus SARS-CoV-2, melatonin is capable of suppressing the damage inflicted by the cytokine storm. The implications of melatonin in susceptibility and treatment of COVID-19 disease are discussed.

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“…References the melatonin levels detected in the mucosa and muscularis of the bovine GIT substantially exceeded the levels observed in the peripheral blood. Melatonin was also detected in the gut of bovine fetuses using the same methodology 86 Bubenik and colleagues conducted several studies on gut melatonin in pigs. 85,87,88 The melatonin content was measured by their RIA and varied from 25 to 875 pg/g across studies and tissues.…”

Section: Authorsmentioning

confidence: 99%

“…They concluded that the melatonin levels detected in the mucosa and muscularis of the bovine GIT substantially exceeded the levels observed in the peripheral blood. Melatonin was also detected in the gut of bovine fetuses using the same methodology 86 …”

Section: Git Melatonin Content In Ratsmentioning

confidence: 99%

The mammalian gastro‐intestinal tract is a NOT a major extra‐pineal source of melatonin

Kennaway

2023

Journal of Pineal Research

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In 1992, a paper reported that the melatonin content of the rat duodenum was 24 000 ± 2000 pg/g tissue (range: 4000–100 000 pg/g) while the pineal melatonin content was 580 000 ± 36 000 pg/g. The data has been used for the last 30 years to infer that the gut produces 400 hundred times more melatonin than the pineal gland and that it is the source of plasma melatonin during the daytime. No‐one has ever challenged the statement. In this review, evidence is summarised from the literature that pinealectomy eliminates melatonin from the circulation and that studies to the contrary have relied upon poorly validated immunoassays that overstate the levels. Similarly studies that have reported increases in plasma melatonin following tryptophan administration failed to account for cross reactivity of tryptophan and its metabolites in immunoassays. The most extraordinary observation from the literature is that in those studies that have measured melatonin in the gut since 1992, the tissue content is vastly lower than the original report, even when the methodology used could be overestimating the melatonin content due to cross reactivity. Using the more contemporary results we can calculate that rather than a 400:1 ratio of duodenum: pineal melatonin, a ratio of 0.05–0.19: 1 is likely. The gut is not a major extra‐pineal source of melatonin; indeed it may well not produce any.

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Melatonin Concentrations in the Gastrointestinal Tissues of Fetal Bovids

Cited by 3 publications

References 23 publications

Localization, Physiological Significance and Possible Clinical Implication of Gastrointestinal Melatonin

Localization, Physiological Significance and Possible Clinical Implication of Gastrointestinal Melatonin

Low melatonin as a contributor to SARS-CoV-2 disease

The mammalian gastro‐intestinal tract is a NOT a major extra‐pineal source of melatonin

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