melanocyte-stimulating hormone
American Heritage Dictionary:
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mel·a·no·cyte-stim·u·lat·ing hormone
(mĕl'ə-nō-sīt'stĭm'yə-lā'tĭng, mə-lăn'ə-) 
n. (Abbr. MSH)
A hormone secreted by the pituitary gland that regulates skin color in humans and other vertebrates by stimulating melanin synthesis in melanocytes and melanin granule dispersal in melanophores. Also called intermedin.
n. (Abbr. MSH)
A hormone secreted by the pituitary gland that regulates skin color in humans and other vertebrates by stimulating melanin synthesis in melanocytes and melanin granule dispersal in melanophores. Also called intermedin.
Oxford Dictionary of Biochemistry:
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melanocyte-stimulating hormone
abbr.: MSH; any of three peptide hormones, α-MSH, β-MSH, and γ-MSH, produced primarily by the intermediate lobe of the pituitary gland, that cause dispersal of melanosomes in melanophores of poikilothermic vertebrates, but whose physiological function in mammals is not understood. Their sequences are all contained within that of proopiomelanocortin (the common precursor of corticotropin and β lipotropin). α-MSH is a tridecapeptide amide (usually acetylated on the N-terminal serine residue) that corresponds to residues 1 — 13 of corticotropin and has the same sequence in almost all animals studied. β-MSH (formerly called intermedin), not believed to be present in humans, corresponds to residues 41 — 58 of β lipotropin and shows greater structural variability. γ-MSH, a putative hormone, is a peptide of variable length that corresponds to part of the so-called cryptic region of proopiomelanocortin. See also melanotropin.
Mosby's Dental Dictionary:
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melanocyte-stimulating hormones
n
MSH, intermedin
A hormone of the middle lobe of the pituitary gland that increases melanin deposition by the melanocytes of the skin.
Wikipedia on Answers.com:
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Melanocyte-stimulating hormone
| Identifiers | |
|---|---|
| Symbol | POMC |
| Entrez | 5443 |
| HUGO | 9201 |
| OMIM | 176830 |
| RefSeq | NM_000939 |
| UniProt | P01189 |
| Other data | |
| Locus | Chr. 2 p23 |
| Clinical data | |
|---|---|
| Pregnancy cat. | ? |
| Legal status | ? |
| Identifiers | |
| ATC code | ? |
| ChEMBL | CHEMBL214332  |
| Chemical data | |
| Formula | ? |
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The melanocyte-stimulating hormones (collectively referred to as MSH or intermedins) are a class of peptide hormones that are produced by cells in the intermediate lobe of the pituitary gland. Synthetic analogs of these naturally occurring hormones have also been developed and researched.
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Contents
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Function
They stimulate the production and release of melanin (melanogenesis) by melanocytes in skin and hair. MSH signals to the brain have effects on appetite and sexual arousal.
In amphibians
In some animals (such as the claw-toed frog Xenopus laevis) production of MSH is increased when the animal is in a dark location. This causes pigment to be dispersed in pigment cells in the toad's skin, making it become darker, and harder for predators to spot. The pigment cells are called melanophores and therefore, in amphibians, the hormone is often called melanophore-stimulating hormone.
In humans
An increase in MSH will cause a darkening in humans too. Melanocyte-stimulating hormone increases in humans during pregnancy. This, along with increased estrogens, causes increased pigmentation in pregnant women. Cushing's syndrome due to excess adrenocorticotropic hormone (ACTH) may also result in hyperpigmentation, such as acanthosis nigricans in the axilla. Most people with primary Addison's have darkening (hyperpigmentation) of the skin, including areas not exposed to the sun; characteristic sites are skin creases (e.g. of the hands), nipple, and the inside of the cheek (buccal mucosa), also old scars may darken. This occurs because melanocyte-stimulating hormone (MSH) and adrenocorticotropic hormone (ACTH) share the same precursor molecule, Pro-opiomelanocortin (POMC).
Different levels of MSH are not the major cause of racial variation in skin colour. However, in many red headed people, and other people who do not tan well, there are variations in their hormone receptors, causing them to not respond to MSH in the blood.
See melanocortin receptor for more information.
Structure of MSH
| proopiomelanocortin derivatives | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| POMC | |||||||||
| γ-MSH | ACTH | β-lipotropin | |||||||
| α-MSH | CLIP | γ-lipotropin | β-endorphin | ||||||
| β-MSH | |||||||||
Melanocyte-stimulating hormone belongs to a group called the melanocortins. This group includes ACTH, alpha-melanocyte-stimulating hormone (α-MSH), beta-melanocyte-stimulating hormone (β-MSH) and gamma-melanocyte-stimulating hormone (γ-MSH); these peptides are all cleavage products of a large precursor peptide called pro-opiomelanocortin (POMC). α-MSH is the most important melanocortin for pigmentation.
The different melanocyte-stimulating hormones have the following amino acid sequences:
| α-MSH: | Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val |
| β-MSH (human): | Ala-Glu-Lys-Lys-Asp-Glu-Gly-Pro-Tyr-Arg-Met-Glu-His-Phe-Arg-Trp-Gly-Ser-Pro-Pro-Lys-Asp |
| β-MSH (porcine): | Asp-Glu-Gly-Pro-Tyr-Lys-Met-Glu-His-Phe-Arg-Trp-Gly-Ser-Pro-Pro-Lys-Asp |
| γ-MSH: | Tyr-Val-Met-Gly-His-Phe-Arg-Trp-Asp-Arg-Phe-Gly |
Synthetic MSH
Synthetic analogs of α-MSH have been developed for human use. Two of the better known are afamelanotide (melanotan-1) in testing by Clinuvel Pharmaceuticals in Australia and bremelanotide by Palatin Technologies, a New Jersey company.
- Afamelanotide (formerly CUV1647) is being investigated as a method of photoprotection in patients with erythropoietic protoporphyria, polymorphous light eruption, actinic keratosis and squamous cell carcinoma (a form of skin cancer).[1]
- An additional analog called Melanotan II causes enhanced libido and erections in most male test subject and arousal with corresponding genital involvement in most female test subjects.[2] Bremelanotide (formerly PT-141) which stemmed from Melanotan II research was previously under development by the New Jersey company for its aphrodisiac effects. These effects are mediated by actions in the hypothalamus on neurons that express MC3 MC3R and MC4 MC4R receptors.
See also
References
- ^ Clinuvel FAQs
- ^ Hadley ME (Oct 2005). "Discovery that a melanocortin regulates sexual functions in male and female humans". Peptides 26 (10): 1687–9. doi:10.1016/j.peptides.2005.01.023. PMID 15996790.
Further reading
- Millington GW (May 2006). "Proopiomelanocortin (POMC): the cutaneous roles of its melanocortin products and receptors". Clin. Exp. Dermatol. 31 (3): 407–12. doi:10.1111/j.1365-2230.2006.02128.x. PMID 16681590.
- Millington GW (2007). "The role of proopiomelanocortin (POMC) neurones in feeding behaviour". Nutr Metab (Lond) 4: 18. doi:10.1186/1743-7075-4-18. PMC 2018708. PMID 17764572. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2018708.
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American Heritage Dictionary
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
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Oxford Dictionary of Biochemistry
Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved.
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Saunders Veterinary Dictionary
Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.
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