Galván Ismael, Alonso-Alvarez Carlos, Negro Juan J
Department of Evolutionary Ecology, Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Científicas, José Gutiérrez Abascal 2, E-28006 Madrid, Spain.
Physiol Biochem Zool. 2012 Jul-Aug;85(4):332-47. doi: 10.1086/666606. Epub 2012 Jun 11.
The synthesis of melanins, which are the most common animal pigments, is influenced by glutathione (GSH), a key intracellular antioxidant. At high GSH levels, pheomelanin (the lightest melanin form) is produced, whereas production of eumelanin (the darkest melanin form) does not require GSH. Oxidative damage typically increases with age, and age-related decreases in GSH have accordingly been found in diverse organisms. Therefore, there should be positive associations between the capacity to produce eumelanic traits, GSH levels, and senescence, whereas there should be negative associations between the capacity to produce pheomelanic traits, GSH levels, and senescence. We explored this hypothesis in a free-ranging population of wild boars Sus scrofa of different ages. As expected from the fact that pheomelanogenesis consumes GSH, levels of this antioxidant in muscle tended to be negatively related to pheomelanization and positively related to eumelanization in pelage, and the degree of pelage pheomelanization was positively related to oxidative damage as reflected by levels of thiobarbituric-acid-reactive substances (TBARS), which is consistent with the hypothesis that pheomelanin synthesis has physiological costs. In our cross-sectional sample, GSH levels did not show senescence effects, and we did not detect senescence effects in pelage melanization. Prime body condition and low TBARS levels were also associated with hair graying, which is attributable to a loss of melanin produced by oxidative stress, thus raising the possibility that hair graying constitutes a signal of resistance to oxidative stress in wild boars. Our results suggest that the degree of melanization is linked to GSH levels in wild boars and that their antioxidant damage shows senescence effects.
黑色素是最常见的动物色素，其合成受细胞内关键抗氧化剂谷胱甘肽（GSH）的影响。在高GSH水平下，会产生褐黑素（最浅的黑色素形式），而真黑素（最深的黑色素形式）的产生则不需要GSH。氧化损伤通常会随着年龄增长而增加，相应地，在多种生物中都发现与年龄相关的GSH水平下降。因此，产生真黑素性状的能力、GSH水平和衰老之间应该存在正相关，而产生褐黑素性状的能力、GSH水平和衰老之间应该存在负相关。我们在不同年龄的自由放养野猪种群中探讨了这一假设。正如褐黑素生成消耗GSH这一事实所预期的那样，肌肉中这种抗氧化剂的水平往往与皮毛中的褐黑素化呈负相关，与真黑素化呈正相关，并且皮毛褐黑素化程度与硫代巴比妥酸反应性物质（TBARS）水平所反映的氧化损伤呈正相关，这与褐黑素合成具有生理成本的假设一致。在我们的横断面样本中，GSH水平未显示出衰老效应，并且我们在皮毛黑化中也未检测到衰老效应。良好的身体状况和低TBARS水平也与毛发变白有关，毛发变白是由于氧化应激导致黑色素流失，因此增加了毛发变白构成野猪抗氧化应激信号的可能性。我们的结果表明，黑化程度与野猪体内的GSH水平有关，并且它们的抗氧化损伤显示出衰老效应。
