Grime reactivation of RBC acetylcholinesterases for biomonitoring

A low-variability method to reactivate blood cholinesterases (ChEs) after p rior exposure of mammals, including humans, to ChE-inhibiting organophospha te esters (OPs) is presented. A concentration of 10 mM pyridine 2-aldoxime methochloride (2-PAM CI) was incubated with intact red blood cells (RBCs) a nd assayed virtually free of interfering oxime and hemoglobin (Hb). Variabi lity was decreased by reducing the number of washing steps and sedimenting RBC ghosts through a 7% sucrose cushion. Statistically significant detectio ns of reactivations as low as 5% with average "false positives" of 3.8% wer e achieved. Relative rates and extent of reactivation after GP treatment of rabbit RBC AChE in vitro were of the order dimethyl- (DDVP) > diethyl- (et hyl paraoxon) >, diisopropyI-substituted (diisopropyl fluorophosphate; DFP) OFs. Rabbit RBC AChE was reactivatable for up to 60 h following dermal exp osure to ethyl parathion and reactivatable for only 12 to 24 h following ex posure to methyl parathion. Reactivation of plasma ChEs with 0.1 mM 2-PAM C l in the same animals was achievable for only 12 to 24 h after ethyl parath ion and for only 1 to 4 h after methyl parathion.