Toxicological Sciences, Vol 49, 78-85, Copyright © 1999 by Society of Toxicology
SL Davis, D Tanaka Jr, RJ Aulerich and SJ Bursian
Abou-Donia et al. (in Toxicologist, Vol. 30, 1996) have reported that
repeated oral administration of the organo-phosphorus compound triphenyl
phosphine (TPPn) to the domestic chicken results in neuropathological
changes in the spinal cord and peripheral nerves, accompanied by ataxia and
paralysis. This study also noted that single doses of TPPn resulted in no
inhibition of the enzymes neuropathy target esterase (NTE) and
acetylcholinesterase (AChE). We undertook the present study to determine
the biochemical, neuropathological, and clinical effects of single doses of
TPPn in the European ferret, a mammalian species shown to be susceptible to
organophosphorus-induced neurotoxicity. Eight 12-week-old ferrets were each
injected subcutaneously with either 250 mg TPPn/kg bw or 500 mg TPPn/kg bw,
or with the peanut oil/ethyl ether vehicle. Twenty-four h after dosing, the
brains of 5 animals from each dose group were examined for NTE and AChE
activities. The remaining 3 animals in each group were observed for 6 days
for the development of clinical signs, after which their brains were
processed for the presence of axonal degeneration using the Fink-Heimer
silver impregnation method. Single injections of TPPn had no effect on the
activities of whole-brain NTE or AChE 24 h after injection. The animals
observed for clinical signs showed increasing trunk and hindlimb ataxia
beginning 4 days after injection, culminating in fore-and hindlimb
paralysis 6 days after injection. All brains exposed to either dose of TPPn
showed widespread axonal degeneration extending from the brainstem and
cerebellum into midbrain and forebrain areas. The results of this study
support the hypothesis that TPPn- induced neurotoxicity is a separate and
distinct form of organophosphorus-induced neurotoxicity not dependent on
NTE inhibition, and therefore not a variant of organophosphorus-induced
delayed neurotoxicity (OPIDN).
ARTICLES
Organophosphorus-induced neurotoxicity in the absence of neuropathy target esterase inhibition: the effects of triphenyl phosphine in the European ferret
Department of Animal Science, Michigan State University, East Lansing 48824, USA.
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