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Induced Hepatic Glutathione and Metabolomic Alterations Following Mixed Pesticide and Fertilizer Exposures in Juvenile Leopard Frogs (Lithobates sphenocephala)
Citation:
Van Meter, R., D. Glinski, Tom Purucker, AND Matt Henderson. Induced Hepatic Glutathione and Metabolomic Alterations Following Mixed Pesticide and Fertilizer Exposures in Juvenile Leopard Frogs (Lithobates sphenocephala). ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 41(1):122-133, (2022). https://doi.org/10.1002/etc.5245
Impact/Purpose:
In the United States, pesticides are licensed under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the statute that governs the registration, distribution, sale, and use of pesticides. As part of this registration process, the registrant must show that using the pesticide according to specifications “will not generally cause unreasonable adverse effects on the environment.” Currently, there is not an accepted regulatory amphibian assessment model for assessing pesticide risk in any country despite the fact that pesticide exposure is an established contributing factor in the decline of amphibians worldwide. A second federal law, the Endangered Species Act, is relevant for the over 50 listed endangered amphibian species in the United States and requires that the EPA consult with other federal agencies to conduct a thorough biological evaluation, including using ecological exposure and effects models, of the impact of the pesticides on these species. Since amphibian-specific exposure and effects data are lacking, amphibian assessments must resort to surrogate data extrapolated from other vertebrate orders. This product directly provides information towards developing sustainable pesticide regulation practices by providing fundamental exposure and biomarker data that can be used to protect non-targeted and endangered amphibian species.
Description:
The increasing use of agrochemicals, alone and in combination, has been implicated as a potential causative factor in the decline of amphibians worldwide. Fertilizers and pesticides are frequently combined into single-use tank mixtures for agricultural applications to decrease costs while meeting the food demands of a growing human population. Limited data are available on the effects of increased nitrogen levels in nontarget species, such as amphibians, and therefore investigating alterations in the nitrogen cycle and its impacts on amphibians needs to be considered in best management practices going forward. The objective of the present study was to elucidate the impact of fertilizer (urea) and herbicide (atrazine and/or alachlor) tank mixtures on the hepatic metabolome of juvenile leopard frogs as well as to investigate alterations in oxidative stress by relating these changes to glutathione (GSH) levels. Herbicide exposure only moderately increased this parameter in amphibians, however, urea alone and in combination with either atrazine or alachlor statistically elevated GSH levels. Interestingly, urea also inhibited pesticide uptake: calculated bioconcentration factors were greatly decreased for atrazine and alachlor when urea was present in the exposure mixture. Metabolomic profiling identified fluxes in hepatic metabolites that are involved in GSH and carbohydrate metabolic processes as well as altered intermediates in the urea cycle. Ultimately, understanding the biological impacts of nitrogenous fertilizers alone and in combination with pesticide exposure will inform best management practices to conserve declining amphibian populations worldwide.
URLs/Downloads:
DOI: Induced Hepatic Glutathione and Metabolomic Alterations Following Mixed Pesticide and Fertilizer Exposures in Juvenile Leopard Frogs (Lithobates sphenocephala)
PubMed Central Link to Manuscript