title: Topical retinoic acid augments ultraviolet light-induced melanogenesis.
abstract: Melanin, the natural pigment found in human skin, absorbs and protects against the ultraviolet (UV) components of sunlight. Melanin production (melanogenesis) is increased by exposure to sunlight, causing a darker skin colour which is regarded as aesthetically pleasing by many humans, who therefore expose themselves to large amounts of potentially damaging sunlight. We have found that topically applied all-trans retinoic acid, a metabolic derivative of vitamin A, greatly enhances UV light-induced melanogenesis: the same preparation on its own had no effect on skin pigmentation. An orally administered retinoid, temarotene, did not have this effect. These observations were made using a lightly pigmented mouse strain, HRA: Skh-2, and confirmed in 2 human volunteers. This is the first time that metabolic derivatives of vitamin A have been shown to augment UV light-induced melanogenesis, suggesting a role for vitamin A in this process.
authors.affiliation: Department of Medicine (Dermatology), University of Sydney, Royal Prince Alfred Hospital, Camperdown, NSW, Australia.
authors.forename: K K
authors.initials: KK
authors.lastname: Ho
authors.forename: G M
authors.initials: GM
authors.lastname: Halliday
authors.forename: R S
authors.initials: RS
authors.lastname: Barnetson
mesh_terms: D000818:Animals; D006801:Humans; D008543:Melanins / Q000096:biosynthesis*; D051379:Mice; D008812:Mice, Hairless; D012176:Retinoids / Q000494:pharmacology*; D012880:Skin Pigmentation / Q000187:drug effects* / Q000528:radiation effects; D014212:Tretinoin / Q000494:pharmacology*; D014466:Ultraviolet Rays
chemical_list: D008543:Melanins; D012176:Retinoids; D014212:Tretinoin; C053595:temarotene