Autofluorescence of melanins induced by ultraviolet radiation and near ultraviolet light. A histochemical and biochemical study
Autofluorescence of melanins induced by ultraviolet radiation and near ultraviolet light. A histochemical and biochemical study
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DOI：
10.1023/a:1017925023408
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发表时间：
2001-05-01
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影响因子：
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通讯作者：
Borovansky, J
中科院分区：
文献类型：
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作者：
Elleder, M;Borovansky, J
使用三种市售封固剂在组织切片中研究了紫外线辐射 (330-380 nm) 和近紫外线 (400-440 nm) 光（统称为紫外线）诱导黑色素的自发荧光。只有 Immu-Mount (Shandon) 适合此用途。无论聚合物的类型如何（真黑素、神经黑色素、褐黑素和卵黄色素），对安装在该介质中的切片中的黑色素进行紫外线照射都会引起强烈的黄色自发荧光。用分离的天然和体外制备的黑色素也观察到自发荧光诱导现象。它被无水条件、叠氮化钠和过氧化氢酶抑制。在平行实验中，在安装在人工富含过氧化氢的介质中或直接安装在 H2O2、Na2O2 或 HIO4 水溶液中的紫外线照射切片中，实现了具有中间荧光阶段的黑色素的快速降解。与紫外线无关的氧化导致黑色素的非荧光分解。这些观察结果表明，共同的机制可能是过氧化氢和紫外线的协同作用导致的氧化攻击，通过强荧光中间体导致黑色素和黑色素样聚合物的完全漂白和氧化分解。活性氧（包括臭氧）被认为是这些实验中的重要反应物。脂类色素与类黑色素色素的不同之处在于其主要的自发荧光，在连续长时间的照射下大部分会褪色。唯一常见的例外是黑变病大肠杆菌色素，其自发荧光在紫外线照射下显着增强。我们的结果证明了自发荧光色素组织化学中的一种新型荧光剂。特别是考虑到脂色素中可能存在基于黑色素的荧光剂，讨论了结果的含义。
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 auto-fluorescence irrespective of the type of the polymer (eumelanin, neuromelanin, pheomelanin and ochronotic pigment). The phenomenon of auto-fluorescence 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 auto-fluorescence, which mostly faded during continuous prolonged irradiation. The only regular exception was melanosis coli pigment, the auto-fluorescence of which was considerably augmented by UV irradiation. Our results demonstrate a novel type of fluorogen in auto-fluorescent pigment histochemistry. The implications of the results are discussed especially in the light of the possible presence of melanin-based fluorogens in lipopigments.