Toxicological Sciences, Vol 47, 16-22, Copyright © 1999 by Society of Toxicology
D Barber, L Correll and M Ehrich
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.
ARTICLES
Comparison of two in vitro activation systems for protoxicant organophosphorous esterase inhibitors
Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg 24061, USA.
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