Action of nerve agents to cholinesterases

Changes of acetylcholinesterase activity in the blood and different organs of the rat following intoxication with sarin, soman, VX and 2-dimethylamino-ethyl-(dimethylamido)phosphonofluoridate (GV) in doses of approximately 2 x LD50 (i.m.) were obtained from literature data and by experiment. The time course of acetylcholinesterase inhibition in the blood, regions of brain and diaphragm and the occurrence of signs and symptoms of poisoning (none, salivation, disturbed ventilation and fasciculations, convulsions or death) were summarized and compared. When blood enzyme activities were 70-100% normal, no signs were seen; at 60-70%, salivation occurred; at less than 30-55%, disturbed ventilation and fasciculations were seen while at 15-30%, convulsions occurred. Less than 10% was fatal. In experiments with narcotized dogs, the blood acetylcholinesterase activity and its reactivatability with trimedoxime were determined following intoxication (i.m.) with the above mentioned four compounds. It can be concluded that acetylcholinesterase activity in the blood corresponds to that in the target organs and can be considered as an appropriate parameter for biological monitoring of nerve gas exposure. Moreover, determination of reactivatability of blood acetylcholinesterase indicates more information than simple enzyme activity determination.