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 drugs hexamethonium, trimethaphan, and hemocholinium and the triethylcholine and cholinesterase/reactivator 2-pyridine aldoxime methochloride (2-PAM) have been shown to be effective in preventing intoxication by diisopropyl phosphorofluoridate (also known as diisopropyl fluorophosphate, DFP) in vivo. We determined their efficacy in preventing cell death (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]uridine incorporation), and on cell protein synthesis (as measured by [H-3]leucine incorporation), The maximal nontoxic doses of the drugs in vitro were determined. All anticholinergic agents studied reduced the cytotoxicity of DFP using one or more parameters. 2-PAM, the cholinesterase reactivator, enhanced the cytotoxicity of DFP on cultured cells at a high concentration (1 mg/mL) and reduced it at a lower concentration (0.3 mg/mL). All four anticholinergic agents were capable of enhancing the uptake of [H-3]thymidine. Only hexamethonium and hemicholinium reversed DFP inhibition of DNA synthesis. RNA synthesis was not affected by any anticholinergic agent and no agent reversed DFP inhibition of RNA synthesis. Protein synthesis was enhanced by every anticholinergic agent except hemicholinium; the inhibition of protein synthesis by DFP was reversed by trimethaphan and triethylcholine. The results indicated that the prophylactory effects of anticholinergics against organophosphate 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 protect against organophosphate intoxication.