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

Comp Biochem Physiol C Toxicol Pharmacol. 2018 Feb;205:34-42. doi: 10.1016/j.cbpc.2018.01.002. Epub 2018 Feb 3.

Abstract

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.

Keywords: Bioaccumulation; Biotransformation; Fish; Imidacloprid; Neonicotinoids; Rainbow trout; Renal clearance; Toxicokinetics.

MeSH terms

  • Animals
  • Aquaculture
  • Bile / metabolism
  • Biotransformation
  • Cholinergic Agents / administration & dosage
  • Cholinergic Agents / blood
  • Cholinergic Agents / metabolism
  • Cholinergic Agents / toxicity*
  • Dose-Response Relationship, Drug
  • Female
  • Half-Life
  • Hepatobiliary Elimination
  • Injections, Intravenous
  • Insecticides / administration & dosage
  • Insecticides / blood
  • Insecticides / metabolism
  • Insecticides / toxicity*
  • Male
  • Metabolic Clearance Rate
  • Microsomes, Liver / drug effects
  • Microsomes, Liver / enzymology
  • Microsomes, Liver / metabolism
  • Neonicotinoids / administration & dosage
  • Neonicotinoids / blood
  • Neonicotinoids / metabolism
  • Neonicotinoids / toxicity*
  • Nitro Compounds / administration & dosage
  • Nitro Compounds / blood
  • Nitro Compounds / metabolism
  • Nitro Compounds / toxicity*
  • Oncorhynchus mykiss / blood
  • Oncorhynchus mykiss / metabolism*
  • Oncorhynchus mykiss / urine
  • Pulmonary Elimination
  • Renal Elimination
  • Sex Factors
  • Tissue Distribution
  • Toxicokinetics
  • Water Pollutants, Chemical / administration & dosage
  • Water Pollutants, Chemical / blood
  • Water Pollutants, Chemical / metabolism
  • Water Pollutants, Chemical / toxicity

Substances

  • Cholinergic Agents
  • Insecticides
  • Neonicotinoids
  • Nitro Compounds
  • Water Pollutants, Chemical
  • imidacloprid