Melanophores are pigmented cells that change the distribution of melanosomes, enabling animals to appear lighter or darker for camouflage, thermoregulation, and protection from ultraviolet radiation. A complex series of hormonal and neural mechanisms regulates melanophore pigment distribution, making these dynamic cells a valuable tool to screen toxicants as they rapidly respond to changes in the environment. We found that maltol, a naturally occurring flavor enhancer and fragrance agent, induces melanophore pigment aggregation in a dose-dependent manner in Xenopus laevis tadpoles. To determine if maltol affects camouflage adaptation, we placed tadpoles into maltol baths situated over either a white or a black background. Maltol induced pigment aggregation in a similar dose-dependent pattern regardless of background color. We also tested how maltol treatment compares to melatonin treatment and found that the degree of pigment aggregation induced by maltol is similar to treatment with melatonin but that maltol induces over a much longer time course. Last, maltol had no effect on mRNA expression in the brain of genes that regulate camouflage-related pigment aggregation. The present results suggest that maltol does not exert its effects via the camouflage adaptation mechanism or via melatonin-related mechanisms. These results are the first to identify a putative toxicological effect of maltol exposure in vivo and rule out several mechanisms by which maltol may exert its effects on pigment aggregation. Environ Toxicol Chem 2020;39:381-395. © 2019 SETAC.

中文翻译：

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增味剂麦芽酚可增加非洲爪蟾（Xenopus laevis Tadpoles）皮肤和神经黑素细胞中色素的聚集。

黑素细胞是色素细胞，可改变黑素体的分布，使动物在伪装，体温调节和免受紫外线辐射时显得更黑或更暗。一系列复杂的激素和神经机制调节黑色素的色素分布，使这些动态细胞成为筛选有毒物质的有价值的工具，因为它们能够快速响应环境变化。我们发现麦芽酚，一种天然存在的增味剂和芳香剂，在非洲爪蟾t中以剂量依赖的方式诱导黑色素色素的聚集。为了确定麦芽酚是否会影响迷彩的适应性，我们将t放入了白色或黑色背景下的麦芽酚浴中。麦芽酚以相似的剂量依赖性模式诱导色素聚集，而不管背景色如何。我们还测试了麦芽酚处理与褪黑激素处理的比较情况，发现麦芽酚诱导的色素聚集程度与褪黑素处理相似，但麦芽酚的诱导时间要长得多。最后，麦芽酚对调节伪装相关色素聚集的基因在脑中的mRNA表达没有影响。目前的结果表明，麦芽酚不会通过迷彩适应机制或褪黑激素相关机制发挥作用。这些结果是首次确定麦芽酚在体内暴露的假定毒理学作用，并排除了麦芽酚可能通过其对色素聚集发挥作用的几种机制。Environ Toxicol Chem 2020； 39：381-395。©2019 SETAC。