USE OF C1300 NEUROBLASTOMA-CELLS TO EVALUATE THE PROTECTIVE VALUE OF HEXAMETHONIUM, TRIMETHAPHAN, HEMICHOLINIUM, AND TRIETHYLCHOLINE AGAINST DIISOPROPYL PHOSPHOROFLUORIDATE TOXICITY

Our intent was to evaluate the C1300 neuroblastoma cell as an in vitro system for studying the mode of action and efficacy of drugs used to treat or prevent organophosphate intoxication. The anticholinergic dru gs hexamethonium, trimethaphan, and hemocholinium and the triethylchol ine and cholinesterase/reactivator 2-pyridine aldoxime methochloride ( 2-PAM) have been shown to be effective in preventing intoxication by d iisopropyl phosphorofluoridate (also known as diisopropyl fluorophosph ate, DFP) in vivo. We determined their efficacy in preventing cell dea th (as measured by trypan blue exclusion) of neuroblastoma cells alone or in combination. We also determined their efficacy in reversing the cytotoxic effects of DFP on cell DNA synthesis (as measured by [H-3]- thymidine incorporation), cell RNA synthesis (as measured by [H-3]urid ine incorporation), and on cell protein synthesis (as measured by [H-3 ]leucine incorporation), The maximal nontoxic doses of the drugs in vi tro were determined. All anticholinergic agents studied reduced the cy totoxicity of DFP using one or more parameters. 2-PAM, the cholinester ase reactivator, enhanced the cytotoxicity of DFP on cultured cells at a high concentration (1 mg/mL) and reduced it at a lower concentratio n (0.3 mg/mL). All four anticholinergic agents were capable of enhanci ng the uptake of [H-3]thymidine. Only hexamethonium and hemicholinium reversed DFP inhibition of DNA synthesis. RNA synthesis was not affect ed by any anticholinergic agent and no agent reversed DFP inhibition o f RNA synthesis. Protein synthesis was enhanced by every anticholinerg ic agent except hemicholinium; the inhibition of protein synthesis by DFP was reversed by trimethaphan and triethylcholine. The results indi cated that the prophylactory effects of anticholinergics against organ ophosphate intoxication, observed in vivo, can be observed using an in vitro cell culture system. Our data suggest that in vitro systems can be used to evaluate the efficacy and toxicity of drugs used to protec t against organophosphate intoxication.