The induction of autofluorescence of melanins by UV radiation (330-380 nm) and near UV (400-440 nm) light (jointly called UV light) was studied in tissue sections using three commercially available mounting media. Only Immu-Mount (Shandon) was found suitable for this purpose. UV irradiation of melanins in sections mounted in this medium induced strong yellow autofluorescence irrespective of the type of the polymer (eumelanin, neuromelanin, pheomelanin and ochronotic pigment). The phenomenon of autofluorescence induction was also observed with isolated natural and in vitro prepared melanins. It was inhibited by anhydrous conditions, sodium azide and catalase. In parallel experiments, rapid degradation of melanins with an intermediate fluorescent stage was achieved in UV-irradiated sections mounted in media artificially enriched with hydrogen peroxide, or directly in aqueous solutions of H2O2, Na2O2 or HIO4. Oxidations not associated with UV light led to nonfluorogenic breakdown of melanins. These observations indicate that the common mechanism may be an oxidative attack resulting from a concerted action of hydrogen peroxide and UV light leading, through strongly fluorescent intermediates, to a complete bleaching and oxidative breakdown of melanin and melanin-like polymers. Reactive oxygen species (including ozone) are considered to be important reactants in these experiments. Lipopigments differ from melanin-like pigments by their primary autofluorescence, which mostly faded during continuous prolonged irradiation. The only regular exception was melanosis coli pigment, the autofluorescence of which was considerably augmented by UV irradiation. Our results demonstrate a novel type of fluorogen in autofluorescent pigment histochemistry. The implications of the results are discussed especially in the light of the possible presence of melanin-based fluorogens in lipopigments.

Institute of Inherited Metabolic Disorders Prague Czech Republic

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Graefes Arch Clin Exp Ophthalmol. 1999 Oct;237(10):830-9 PubMed

Arch Biochem Biophys. 1999 Nov 1;371(1):63-9 PubMed

Cell Mol Biol (Noisy-le-grand). 1999 Nov;45(7):1119-29 PubMed

Folia Biol (Praha). 1999;45(2):47-52 PubMed

J Neurochem. 2000 Apr;74(4):1758-65 PubMed

Toxicology. 2000 Apr 14;145(2-3):85-101 PubMed

Acc Chem Res. 2000 May;33(5):307-13 PubMed

Invest Ophthalmol Vis Sci. 2001 Jan;42(1):241-6 PubMed

Ann N Y Acad Sci. 1963 Feb 15;100:497-533 PubMed

Science. 1965 Jul 23;149(3682):439-40 PubMed

Pigment Cell Res. 1991 Oct;4(4):172-9 PubMed

Biochem Biophys Res Commun. 1978 Sep 29;84(2):335-41 PubMed

J Biol Chem. 1990 Jul 25;265(21):12410-6 PubMed

Vision Res. 1990;30(9):1291-303 PubMed

Am J Clin Pathol. 1986 Oct;86(4):556-7 PubMed

Arch Dermatol Res. 1986;279(1):54-8 PubMed

Vopr Med Khim. 1989 May-Jun;35(3):139-43 PubMed

Biokhimiia. 1989 Jun;54(6):992-8 PubMed

Arch Biochem Biophys. 1985 May 15;239(1):226-33 PubMed

Biochem Biophys Res Commun. 1985 Sep 16;131(2):659-65 PubMed

Pigment Cell Res. 1987;1(3):171-5 PubMed

Am J Pathol. 1988 Jun;131(3):465-76 PubMed

Invest Radiol. 1988 Aug;23(8):609-15 PubMed

Anal Biochem. 1986 Dec;159(2):249-52 PubMed

Comp Biochem Physiol B. 1976;53(4):521-3 PubMed

Anal Biochem. 1973 Nov;56(1):91-9 PubMed

J Neuropathol Exp Neurol. 1969 Jul;28(3):419-41 PubMed

Invest Ophthalmol Vis Sci. 1978 Jul;17(7):583-600 PubMed

Photochem Photobiol. 1982 Jun;35(6):881-5 PubMed

Photochem Photobiol. 1982 Aug;36(2):251-4 PubMed

Physiol Chem Phys. 1982;14(4):363-74 PubMed

Arch Int Physiol Biochim Biophys. 1994 May-Jun;102(3):175-81 PubMed

Cell Tissue Res. 1994 May;276(2):273-9 PubMed

Nature. 1993 Feb 25;361(6414):724-6 PubMed

Sb Lek. 1996;97(1):49-70 PubMed