Worek_1996_Arch.Toxicol_70_497

The new bispyridinium oximes HI 6 and HL 7 are promising antidotes against poisoning by highly toxic organophosphorus compounds, i.e. nerve agents. Until now, their ability to reactivate pesticide inhibited human acetylcholinesterase (AChE) has not been elucidated. For this purpose human erythrocyte AChE (EC 3.1.1.7) was inhibited (30 min) by chlorfenvinphos, dichlorvos, dicrotophos, heptenophos, mevinphos, monocrotophos, paraoxon, phosphamidon, trichlorfon, malaoxon, omethoate, oxydemeton-methyl or methamidophos by 85-98% of control. After removal of excess inhibitor, obidoxime, pralidoxime (2-PAM), HI 6 or HL 7 (10, 30 or 100 mumol/l) were added and the AChE activity was measured spectrophotometrically at various times thereafter (5-60 min). The oximes significantly, but not completely, reactivated organophosphate inhibited AChE. The velocity and extent of reactivation were dependent on the oxime and its concentration. In all cases obidoxime was superior to the three other oximes, followed by HL 7, 2-PAM and HI 6. In most cases obidoxime and HL 7 were most effective at 10 or 30 mumol/l while 2-PAM and HI 6 needed 100 mumol/l. These data suggest that 2-PAM HI 6 and HL 7 are less patent than obidoxime in reactivating human AChE inhibited by organophosphate pesticides.