Alpha-MSH causes a small rise in cAMP but has no effect on basal or ultraviolet-stimulated melanogenesis in human melanocytes.
The effects of alpha-melanocyte stimulating hormone (alpha-MSH) were studied on levels of cyclic adenosine 3',5'-monophosphate (cAMP), melanin content and response to ultraviolet radiation (UVR) in cultured human melanocytes (HuMC). Foreskin HuMC were cultured in a hormone-supplemented system not dependent on the presence of phorbol esters. Following addition of alpha-MSH (10(-6) M) there was a rise in cAMP levels maximal between 5 and 15 min to 9.4 +/- 3.2 pM/10(5) cells, while control levels were 3.6 +/- 0.7 pM/10(5) cells. After 7 days' culture in the presence of alpha-MSH (10(-8) -10(-6) M) the melanin content increased by only 35%, whereas Forskolin (10(-5) M) induced a 9.5-fold rise in cAMP after 5 min and a 10.9-fold rise in melanin content after 7 days. When HuMC were irradiated daily for 6 days with UVR (Helarium fluorescent lamps emitting 20% UVB, 80% UVA) melanin content rose 2.7-fold (SE 0.3). This was unchanged or slightly reduced in the presence of alpha-MSH (10(-8)-10(-6) M). Parallel observations on Cloudman S91 melanoma cells showed that alpha-MSH caused only an 80% increase in melanin content after 4 days. The rise in melanin content induced by three daily UV-irradiations (2.4-fold, SE 0.5) was unchanged by alpha-MSH (10(-8)-10(-6) M). Although alpha-MSH induces a small rise in cAMP in HuMC this does not result in melanogenesis, and the response to UVR is not affected by alpha-MSH in either HuMC or S91 cells.
Department of Dermatology, Royal Victoria Infirmary, Newcastle upon Tyne, U.K.
P S
PS
Friedmann
F
F
Wren
J
J
Buffey
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S
Macneil
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis*; D006801:Humans; D008297:Male; D008543:Melanins / Q000096:biosynthesis*; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D008544:Melanocytes / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D008545:Melanoma / Q000378:metabolism; D012878:Skin Neoplasms / Q000378:metabolism; D013997:Time Factors; D014466:Ultraviolet Rays
D008543:Melanins; D005576:Colforsin; D009074:Melanocyte-Stimulating Hormones; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine