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Characterization of deltamethrin metabolism by rat plasma and liver microsomes.

Publication ,  Journal Article
Anand, SS; Bruckner, JV; Haines, WT; Muralidhara, S; Fisher, JW; Padilla, S
Published in: Toxicology and applied pharmacology
April 2006

Deltamethrin, a widely used type II pyrethroid insecticide, is a relatively potent neurotoxicant. While the toxicity has been extensively examined, toxicokinetic studies of deltamethrin and most other pyrethroids are very limited. The aims of this study were to identify, characterize, and assess the relative contributions of esterases and cytochrome P450s (CYP450s) responsible for deltamethrin metabolism by measuring deltamethrin disappearance following incubation of various concentrations (2 to 400 microM) in plasma (esterases) and liver microsomes (esterases and CYP450s) prepared from adult male rats. While the carboxylesterase metabolism in plasma and liver was characterized using an inhibitor, tetra isopropyl pyrophosphoramide (isoOMPA), CYP450 metabolism was characterized using the cofactor, NADPH. Michaelis-Menten rate constants were calculated using linear and nonlinear regression as applicable. The metabolic efficiency of these pathways was estimated by calculating intrinsic clearance (Vmax/Km). In plasma, isoOMPA completely inhibited deltamethrin biotransformation at concentrations (2 and 20 microM of deltamethrin) that are 2- to 10-fold higher than previously reported peak blood levels in deltamethrin-poisoned rats. For carboxylesterase-mediated deltamethrin metabolism in plasma, Vmax=325.3+/-53.4 nmol/h/ml and Km=165.4+/-41.9 microM. Calcium chelation by EGTA did not inhibit deltamethrin metabolism in plasma or liver microsomes, indicating that A-esterases do not metabolize deltamethrin. In liver microsomes, esterase-mediated deltamethrin metabolism was completely inhibited by isoOMPA, confirming the role of carboxylesterases. The rate constants for liver carboxylesterases were Vmax=1981.8+/-132.3 nmol/h/g liver and Km=172.5+/-22.5 microM. Liver microsomal CYP450-mediated biotransformation of deltamethrin was a higher capacity (Vmax=2611.3+/-134.1 nmol/h/g liver) and higher affinity (Km=74.9+/-5.9 microM) process than carboxylesterase (plasma or liver) detoxification. Genetically engineered individual rat CYP450s (Supersomes) were used to identify specific CYP450 isozyme(s) involved in the deltamethrin metabolism. CYP1A2, CYP1A1, and CYP2C11 in decreasing order of importance quantitatively, metabolized deltamethrin. Intrinsic clearance by liver CYP450s (35.5) was more efficient than that by liver (12.0) or plasma carboxylesterases (2.4).

Duke Scholars

Published In

Toxicology and applied pharmacology

DOI

EISSN

1096-0333

ISSN

0041-008X

Publication Date

April 2006

Volume

212

Issue

2

Start / End Page

156 / 166

Related Subject Headings

  • Toxicology
  • Rats, Sprague-Dawley
  • Rats
  • Pyrethrins
  • Nitriles
  • Microsomes, Liver
  • Male
  • Insecticides
  • In Vitro Techniques
  • Esterases
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Anand, S. S., Bruckner, J. V., Haines, W. T., Muralidhara, S., Fisher, J. W., & Padilla, S. (2006). Characterization of deltamethrin metabolism by rat plasma and liver microsomes. Toxicology and Applied Pharmacology, 212(2), 156–166. https://doi.org/10.1016/j.taap.2005.07.021
Anand, Sathanandam S., James V. Bruckner, Wendy T. Haines, Srinivasa Muralidhara, Jeffrey W. Fisher, and Stephanie Padilla. “Characterization of deltamethrin metabolism by rat plasma and liver microsomes.Toxicology and Applied Pharmacology 212, no. 2 (April 2006): 156–66. https://doi.org/10.1016/j.taap.2005.07.021.
Anand SS, Bruckner JV, Haines WT, Muralidhara S, Fisher JW, Padilla S. Characterization of deltamethrin metabolism by rat plasma and liver microsomes. Toxicology and applied pharmacology. 2006 Apr;212(2):156–66.
Anand, Sathanandam S., et al. “Characterization of deltamethrin metabolism by rat plasma and liver microsomes.Toxicology and Applied Pharmacology, vol. 212, no. 2, Apr. 2006, pp. 156–66. Epmc, doi:10.1016/j.taap.2005.07.021.
Anand SS, Bruckner JV, Haines WT, Muralidhara S, Fisher JW, Padilla S. Characterization of deltamethrin metabolism by rat plasma and liver microsomes. Toxicology and applied pharmacology. 2006 Apr;212(2):156–166.
Journal cover image

Published In

Toxicology and applied pharmacology

DOI

EISSN

1096-0333

ISSN

0041-008X

Publication Date

April 2006

Volume

212

Issue

2

Start / End Page

156 / 166

Related Subject Headings

  • Toxicology
  • Rats, Sprague-Dawley
  • Rats
  • Pyrethrins
  • Nitriles
  • Microsomes, Liver
  • Male
  • Insecticides
  • In Vitro Techniques
  • Esterases