Comparison of two in vitro activation systems for protoxicant organophosphorous esterase inhibitors.

In order to perform in vitro testing of esterase inhibition caused by organophosphorous (OP) protoxicants, simple, reliable methods are needed to convert protoxicants to their esterase-inhibiting forms. Incubation of parathion or chlorpyrifos with 0.05% bromine solution or uninduced rat liver microsomes (RLM) resulted in production of the corresponding oxygen analogs of these OP compounds and markedly increased esterase inhibition in SH-SY5Y human neuroblastoma cells. Neither activation system affected cell viability or the activity of AChE or NTE in the absence of OP compounds. Although parathion and chlorpyrifos were activated by RLM, bromine activation required fewer steps and produced more esterase inhibition for a given concentration of chlorpyrifos. However, RLM activation of OP protoxicants produced metabolites other than oxygen analogs and may, therefore, be more relevant as a surrogate for OP biotransformation in vivo. This methodology makes the use of intact cells for in vitro testing of esterase inhibition caused by protoxicant organophosphate compounds a viable alternative to in vivo tests.
AuthorsD Barber, L Correll, M Ehrich
JournalToxicological sciences : an official journal of the Society of Toxicology (Toxicol Sci) Vol. 47 Issue 1 Pg. 16-22 (Jan 1999) ISSN: 1096-6080 [Print] UNITED STATES
PMID10048149 (Publication Type: Comparative Study, Journal Article)
Chemical References
  • Cholinesterase Inhibitors
  • Enzyme Inhibitors
  • Organophosphorus Compounds
  • Parathion
  • Esterases
  • Carboxylic Ester Hydrolases
  • neurotoxic esterase
  • Chlorpyrifos
  • Bromine
  • Animals
  • Bromine (toxicity)
  • Carboxylic Ester Hydrolases (antagonists & inhibitors)
  • Chlorpyrifos (toxicity)
  • Cholinesterase Inhibitors (metabolism, toxicity)
  • Chromatography, High Pressure Liquid
  • Enzyme Inhibitors (metabolism, toxicity)
  • Esterases (antagonists & inhibitors)
  • Humans
  • Male
  • Microsomes, Liver (drug effects)
  • Neuroblastoma
  • Organophosphorus Compounds (metabolism, toxicity)
  • Parathion (toxicity)
  • Rats
  • Rats, Sprague-Dawley
  • Tumor Cells, Cultured

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