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The functional set-up of a static inhalation device is described. The closed system consists of a reservoir for the circulating test gas, an inhalator for "nose-only" exposure of 10 rats, and analyzers for the test gas and CO2. It has an overall volume of 200 liters. The following LCt50 values for rats exposed to noxious vapors were determined: DFP 3629, sarin 191, and soman 211 mg X min X m-3. Pretreatment with atropine (10 mg/kg) together with the oximes Toxogonin or HJ6 (each 13 mg/kg) 10 min before the exposure raised the LCt50 of sarin by a factor of 2.5 and 14, respectively. In case of soman poisoning, only HJ6 (50 mg/kg) together with atropine was effective, which increased the LCt50 by a factor of 7.

The influence of 27 possible effectors, mostly bispyridinium salts, upon the dealkylation (aging) of soman-inhibited acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) was examined at pH 7.6 and 25 degrees C. In the absence of effectors, the rate constant of the aging process was 4.0. 10(-2) min-1. At 2 mM, the strongest inhibitor reduced the rate to 0.8. 10(-2) min-1, whereas it was raised to 8.2. 10(-2) min-1 by the most potent accelerator.

From human blood concentrates erythrocyte "ghosts" were prepared. These and an enzyme solution, obtained by Triton X 100 treatment of the ghosts, were reacted with 1.2.2-trimethylpropyl-methyl-phosphonylfluoridate (soman). The rate constants of inhibition of the membrane bound and solubilized acetylcholinesterase (AChE) were determined at 3 degrees C, pH 8 and 9 to be 2 X 10(7) and 1.4 X 10(7) mol-1 min-1, respectively. Ageing of the phosphonylated AChE occurred with rate constants of 3.5 X 10(-2) (ghost bound) and 1.3 X 10(-2) (solubilized) min-1 at 3 degrees C, pH 8. 5 X 10(-4) mol/l atropine decreased the ageing rate by 50%. Reactivation of the non aged phosphonyl-AChE by several pyridinium oximes was enhanced by atropine with the ghost-bound enzyme; the reactivation of the phosphonylated solubilized enzyme, however, was not affected by atropine.

The influence of pH and temperature upon the dealkylation (aging) of soman-inhibited acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) was investigated. The pH-rate profile, as measured at 5 degrees C, shows a maximum aging rate at pH 5.0 and indicates the involvement of two ionizable groups with pKa values of 6.0 and 4.5. The pH-rate profile was not changed essentially by the two effector compounds, semicarbazide and HH54. the activation energy of aging at pH 7.0 was determined as to 6.12 x 10(4) J/mol; it was lowered by the accelerator of aging semicarbazide to 5.28 x 10(4) J/mol and increased to 9.42 x 10(4) J/mol by the retarding compound HH54.