Studies have shown that olfactory-mediated behaviors that are critical to survival can be disrupted by exposure to certain metals. Polluted waterways often contain elevated levels of metals, yet only a subset have been characterized for their potential to cause olfactory toxicity. A larval zebrafish behavioral assay was developed to characterize concentration-response curves for zinc (Zn), hexavalent chromium (Cr), and arsenate (As) olfaction inhibition. Cadmium (Cd), an established olfactory toxicant, was used as a positive control. As expected, following a 24-hour exposure to Cd, we observed a reduced response to taurocholic acid (TCA), a substrate for ciliated olfactory sensory neurons (OSNs), thus validating the behavioral assay. Zn exposure similarly decreased the olfactory response toward TCA, (IC₅₀: 36 μg/L and 76 μg/L, for Cd and Zn, respectively). The response towards a secondary odorant L-cysteine (Cys), a substrate for ciliated and microvillous OSNs, was significantly altered by both Cd and Zn exposure, although the response to Cys was not completely removed in Zn treated larvae, suggesting preferential toxicity towards ciliated OSNs. No significant changes in olfactory responses were observed following Cr and As exposures. Exposures to binary mixtures of Cd and Zn indicated that Zn had a protective effect against Cd toxicity at low Zn concentrations. QuantiGene (QDP) RNA analysis revealed Cd to be a potent inducer of metallothionein 2 (mt2) mRNA in zebrafish larvae, and Zn to be a weak mt2 inducer, suggesting a protective role of mt2 in Cd and Zn olfactory injury. By contrast, QDP analysis of eight other genes important in mitigating the effects of oxidative stress suggested an antioxidant response to Cd, but not Zn, As, and Cr suggesting that oxidative stress was not a primary mechanism of Zn-induced olfactory dysfunction. In summary, our study indicates that Zn inhibits zebrafish olfaction at environmental concentrations and may potentially mitigate Cd induced olfactory dysfunction when present in mixtures. The zebrafish behavioral trough assay incorporating the odorants L-cysteine and TCA is an effective assay to assess the effects of metals on olfactory function.

研究表明，对生存至关重要的嗅觉介导行为可以通过暴露于某些金属而破坏。受污染的水道通常含有较高水平的金属，但只有一部分因其可能引起嗅觉毒性而被表征。进行了幼虫斑马鱼行为测定，以表征锌（Zn），六价铬（Cr）和砷酸盐（As）嗅觉抑制的浓度-响应曲线。确立的嗅觉有毒物质镉（Cd）被用作阳性对照。正如预期的那样，在24小时暴露于Cd之后，我们观察到对牛磺胆酸（TCA）（纤毛嗅觉感觉神经元（OSNs）的底物）的反应减少，从而验证了行为分析。锌暴露同样降低了对三氯乙酸的嗅觉反应（IC ₅₀：Cd和Zn分别为36μg/ L和76μg/ L）。镉和锌暴露均显着改变了对次级气味L-半胱氨酸（Cys）（纤毛和微毛OSNs的底物）的响应，尽管在Zn处理的幼虫中对Cys的响应并未完全消除，这表明对纤毛的优先毒性OSN。铬和砷暴露后，没有观察到嗅觉反应的显着变化。暴露于Cd和Zn的二元混合物中表明，Zn在低Zn浓度下对Cd毒性具有保护作用。QuantiGene（QDP）RNA分析显示，Cd是斑马鱼幼虫中金属硫蛋白2（mt2）mRNA的有效诱导剂，而Zn是弱mt2诱导剂，表明mt2在Cd和Zn嗅觉损伤中具有保护作用。相比之下，QDP分析了另外8个对减轻氧化应激的影响很重要的基因，表明对Cd的抗氧化反应，但对Zn，As和Cr的抗氧化反应却不高，这表明氧化应激不是Zn诱导的嗅觉功能障碍的主要机制。总而言之，我们的研究表明，Zn在环境浓度下会抑制斑马鱼的嗅觉，并且当混合物中存在Zn时，可能会缓解Cd诱导的嗅觉功能障碍。结合了L-半胱氨酸和TCA气味的斑马鱼行为谷分析是评估金属对嗅觉功能影响的有效分析方法。我们的研究表明，锌在环境浓度下会抑制斑马鱼的嗅觉，并且当存在于混合物中时，可能会缓解镉诱导的嗅觉功能障碍。结合了L-半胱氨酸和TCA气味的斑马鱼行为谷分析是评估金属对嗅觉功能影响的有效分析方法。我们的研究表明，锌在环境浓度下会抑制斑马鱼的嗅觉，并且当存在于混合物中时，可能会缓解镉诱导的嗅觉功能障碍。结合了L-半胱氨酸和TCA气味的斑马鱼行为谷分析是评估金属对嗅觉功能影响的有效分析方法。