Analysis of earthworm sublethal toxic responses to atrazine exposure using 1 H nuclear magnetic resonance (NMR)-based metabolomics.

Abstract

Atrazine toxicity to earthworms is still not fully understood, particularly at sublethal concentrations. Because of the ubiquity of atrazine in the environment, it is imperative to understand the impacts of atrazine presence to soil-dwelling organisms. To examine this in detail, we used 1 H nuclear magnetic resonance (NMR)-based metabolomics to elucidate earthworm (Eisenia fetida) responses after 48 h of atrazine exposure in contact tests. Earthworms were exposed to 4 sublethal concentrations of 362.4, 181.2, 90.6, and 45.3 ng/cm2 , which correspond to 1/8th, 1/16th, 1/32nd, and 1/64th of the median lethal concentration (LC50) values, respectively. After exposure, polar metabolites were isolated from earthworm tissues and analyzed using 1 H NMR spectroscopy. Sublethal atrazine exposure induced a nonmonotonic response with respect to exposure concentration and caused an overall suppression in earthworm metabolism. Maltose, fumarate, malate, threonine/lactate, adenosine-5'-triphosphate (ATP), betaine, scyllo-inositol, glutamate, arginine, and glutamine were the metabolites identified as most sensitive to atrazine exposure. These observed fluctuations in the metabolic profile suggest that atrazine reduced ATP synthesis and negatively impacted the health of earthworms after acute sublethal exposure. Our study also demonstrates the utility of NMR-based metabolomics for the basic assessment of sublethal toxicity, which can then be used for more targeted approaches with other molecular techniques. Environ Toxicol Chem 2018;37:473-480. © 2017 SETAC.