Toxicokinetics of the neonicotinoid insecticide imidacloprid in rainbow trout (Oncorhynchus mykiss)

John A. Frew, Jacob T. Brown, Patrick N. Fitzsimmons, Alex D. Hoffman, Martin Sadilek, Christian E. Grue, John W. Nichols

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3 Scopus citations


Studies were conducted to determine the distribution and elimination of imidacloprid (IMI) in rainbow trout. Animals were injected with a low (47.6 μg/kg), medium (117.5 μg/kg) or high (232.7 μg/kg) dose directly into the bloodstream and allowed to depurate. The fish were then sampled to characterize the loss of IMI from plasma and its appearance in expired water (all dose groups) and urine (medium dose only). In vitro biotransformation of IMI was evaluated using trout liver S9 fractions. Mean total clearance (CLT) values determined by non-compartmental analysis of plasma time-course data were 21.8, 27.0 and 19.5 mL/h/kg for the low, medium and high dose groups, respectively. Estimated half-lives for the same groups were 67.0, 68.4 and 68.1 h, while fitted values for the steady-state volume of distribution (VSS) were 1.72, 2.23 and 1.81 L/kg. Branchial elimination rates were much lower than expected, suggesting that IMI is highly bound in blood. Renal clearance rates were greater than measured rates of branchial clearance (60% of CLT in the medium dose group), possibly indicating a role for renal membrane transporters. There was no evidence for hepatic biotransformation of IMI. Collectively, these findings suggest that IMI would accumulate in trout in continuous waterborne exposures.

Original languageEnglish (US)
Pages (from-to)34-42
Number of pages9
JournalComparative Biochemistry and Physiology Part - C: Toxicology and Pharmacology
StatePublished - Feb 2018

Bibliographical note

Funding Information:
The authors would like to thank the School of Aquatic and Fishery Sciences , Washington Cooperative Fish and Wildlife Research Unit , and the Department of Chemistry at the UW , the U.S. EPA Mid-Continent Ecology Division , and the College of Pharmacy at the University of Minnesota for financial and/or in-kind support. The Washington Cooperative Research Unit is supported by the U.S. Geological Survey, the Washington State Departments of Ecology, Fish and Wildlife, and Natural Resources, and the UW and Washington State University. Part of the present study was conducted in partial fulfillment of a doctoral degree by the senior author at the UW. We thank Dr. Russell Erickson and 2 anonymous reviewers for their comments on earlier drafts of the manuscript, and Compliance Services International for providing access to statistical software. This document has been subjected to review by the U.S. EPA National Health and Effects Research Laboratory and approved for publication. Approval does not signify that the contents reflect the views of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

Publisher Copyright:
© 2018 Elsevier Inc.

Copyright 2020 Elsevier B.V., All rights reserved.


  • Bioaccumulation
  • Biotransformation
  • Fish
  • Imidacloprid
  • Neonicotinoids
  • Rainbow trout
  • Renal clearance
  • Toxicokinetics

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