Modification of the rate of aging of diisopropylfluorophosphate-inhibited neuropathy target esterase of hen brain.

This study was aimed to investigate the possibility of modifying the rate of aging of diisopropylfluorophosphate-inhibited neuropathy target esterase (NTE) of hen brain. This reaction on NTE occurs with a half-time of 7.4 min. Atropine was effective in decreasing the rate of aging on DFP-inhibited NTE and this effect was time- and concentration-dependent. Atropine was also a weak but progressive inhibitor of NTE activity (I50 = 80 mM) and this reaction appears to be reversible at lower atropine concentrations. Among compounds containing oxime functional groups only OPAB, having longer methylene chain and being more lipophylic than other oximes usually used in acetylcholinesterase (AChE) reactivation studies, was effective in decreasing the rate of aging on DFP-inhibited NTE. However, when atropine and oximes were used together we have obtained a potentiating and/or synergistic effect which was most significant with combination of atropine and TMB-4 giving up to a 15-fold decrease in the rate of aging reaction. The efficacy of this particular combination was concentration-dependent. We have also discussed similarities and differences in aging reaction occurring on NTE and AChE.