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Neuroendocrinology Letters Vol. 20 No. 5 Contents
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Neuroendocrinology Letters incl. Psychoneuroimmunology & Chronobiology. Review Papers.
ISSN 0172–780X Copyright © 1999 Neuroendocrinology Letters

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NEL VOL. 20  No. 5
INVITED NEL REVIEW
Full text pdf (363kb)
1999; 20:265–282
pii: NEL200599R01
The actions of melanin and melanocyte stimulating hormone (MSH)
by Natalie Rasmussen, Francine Nelson, Piyarat Govitrapong & Manuchair Ebadi

Key words:
melanocyte; keratin; tyrosinase; melanin; eumelanins; pheomelanins; melanocyte stimulating hormone; pigmentation; albinism; ultraviolet radiation; solar radiation; dermatotherapeutics

Abstract
The skin, the largest organ of the body, plays an important role in the total metabolism of several hormones.
Melanin, the major product of the melanocyte, is largely responsible for the coloring of skin. Melanin is a complex of insoluble, polyquinone, brown or red pigment and protein, formed by the oxidation of tyrosine and 3,4-dihydroxyphenylalanine in the presence of tyrosinase. There exists two main groups of melanin: the black to dark-brown insoluble eumelanins and the yellow to reddish brown, alkali-soluble pheomelanins. MSH, ACTH and b-lipoprotein are able to influence skin pigmentation. The functions attributed to melanins are acting as a barrier against ionizing radiation; participating in developmental processes, serving as a cosmetic entity, and scavenging cytotoxic radicals and intermediates. Melanocytes express numerous receptors that allow interaction with other cells in their microenvironment, including keratinocytes and the immune component of the skin Langerhans cells. Albinism represents a group of inherited abnormalities that present with congenital hypopigmentation that can involve the skin, hair, and eyes (oculocutaneous albinism) or be limited primarily to the eyes (ocular albinism). The inherited disorders of keratin include epidermolysis bullosu simplex causing cell degeneration within the basal layer. Sunlight and ultraviolet radiation from artificial light sources could be tonic or toxic to human skin. The harmful effects of solar radiation are skin cancer, photosensitivity diseases, sunburn, photoallergy, photoimmunologic alterations, cataracts, mutations, skin aging and phototoxicity. Sunscreen chemicals protect the skin against ultraviolet radiation.

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Copyright © Neuroendocrinology Letters 1999
All rights reserved. No part may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or ortherwise, without prior written permission from the Editor-in-Chief.