Nonnutritive sweeteners used in food and beverage products are widespread, persistent aquatic pollutants. Despite this, their impact on aquatic organisms, particularly vertebrates, is not well-studied. Recent findings in rodents suggest sucralose, a chlorinated disaccharide, alters thyroid hormone (TH) metabolism. Because amphibian tadpole metamorphosis is TH-dependent, we hypothesized sucralose may alter signaling for this postembryonic developmental process. The present study used the American bullfrog, Rana (Lithobates) catesbeiana, as a sensitive, environmentally relevant model for testing TH disruption in the absence and presence of thyroxine (T₄), a hormone that induces metamorphosis. Premetamorphic R. catesbeiana tadpoles were immersed in 1-, 15-, and 32-mg/L sucralose solutions ± 5 nM (3.9 µg/L) thyroxine (T₄) for 48 h. RNA transcripts encoding thyroid hormone receptors alpha and beta (thra and thrb) and TH-induced basic region leucine zipper protein (thibz) were analyzed in four tissues: back skin, liver, olfactory epithelium, and tail fin, using reverse transcription quantitative real-time PCR (RT-qPCR). We found that sucralose altered the expression of fundamental TH-response genes involved in anuran metamorphosis in a tissue- and TH-status dependent manner. As organochlorines induce xenobiotic metabolism, we isolated and characterized three novel R. catesbeiana gene transcripts involved in xenobiotic metabolism: pregnane X receptor (nr1i2), constitutive androstane receptor (nr1i3), and cytochrome p450 3a4 (cyp3a4). We analyzed their expression using RT-qPCR and found evidence of their modulation by sucralose. To our knowledge, these data are the first to show xenobiotic and thyroid-disrupting activities in amphibians and further investigations into cumulative effects of environmental sucralose exposure are warranted.

食品和饮料产品中使用的非营养性甜味剂是广泛存在的持久性水污染物。尽管如此，尚未充分研究它们对水生生物，特别是脊椎动物的影响。啮齿动物的最新发现表明，三氯蔗糖是一种氯化二糖，可改变甲状腺激素（TH）的代谢。因为两栖动物的meta变态是TH依赖的，所以我们假设三氯蔗糖可能会改变这种胚胎后发育过程的信号传导。本研究使用美国牛蛙Rana（Lithobates）catesbeiana作为敏感且与环境相关的模型，在缺乏和存在甲状腺素（T ₄）的情况下测试TH破坏，甲状腺素（T ₄）会诱发变态。前变态的R. catesbeiana将浸入1、15和32 mg / L三氯蔗糖溶液±5 nM（3.9 µg / L）甲状腺素（T ₄）中48小时。使用逆转录定量实时荧光定量分析技术，在四个组织中分析了编码甲状腺激素受体α和β（thra和thrb）以及TH诱导的碱性区域亮氨酸拉链蛋白（thibz）的RNA转录本。时间PCR（RT-qPCR）。我们发现三氯蔗糖以组织和TH状态依赖的方式改变了参与anuran变态的基本TH反应基因的表达。由于有机氯诱导异种生物代谢，我们分离并鉴定了三种新颖的R. catesbeiana涉及异种生物代谢的基因转录物：孕烷X受体（nr1i2），组成型雄烷受体（nr1i3）和细胞色素p450 3a4（cyp3a4）。我们使用RT-qPCR分析了它们的表达，并发现了三氯蔗糖对其调节的证据。据我们所知，这些数据是第一个显示两栖动物异生物和破坏甲状腺活性的数据，因此有必要对环境中三氯蔗糖暴露的累积影响进行进一步研究。