Avian whole-brain spheroid cultures: applications in pesticide toxicity

The adult hen is the species of choice when assessing the potential of orga nophosphate compounds (OPs) to evoke OF-induced delayed neuropathy (OPIDN), OPIDN has been shown to depend on the irreversible covalent binding of cer tain OPs to the enzyme neuropathy target esterase (NTE). Levels of this enz yme in human brain are similar to those in avian species. We have previousl y shown that the hen embryo whole brain spheroids are histotypically simila r to adult brain and express measurable levels of acetylcholine esterase (A ChE) and NTE, the key enzymes in mechanisms of OF toxicity. Single-cell suspensions were prepared from meninges-free 7 day in ovo hen b rains. Cells were grown in serum-free media and incubated on an orbital sha ker at 37 degrees C in 5% carbon dioxide humidified air, Spheroids can be m aintained long-term in culture and allow the effects of repeated dose and r ecovery studies to be conducted. Hen embryo brain spheroids were exposed to varying concentrations of tri-o-cresyl phosphate, leptophos and its metabo lite leptophos oxon at day 14 in vitro and the effects on the activity of A ChE and NTE measured. Whilst current legislation regarding toxicity testing of OPs requires the use of animals, our in vitro model provides a potentia l pre-screen for novel chemical entities and commercial OP mixture variants . Such an approach should refine and reduce the number of animals used in d evelopment of new materials. (C) 2000 Society of Chemical Industry.