Low-Level Cyclosarin (GF) Vapor Exposure in Rats: Effect of Exposure Concentration and Duration on Pupil Size

摘要

Probability of cyclosarin (GF) miosis (defined as post-exposure pupil diameter 50% or less of pre-exposure pupil diameter) was estimated in rats exposed to combinations of exposure concentration and duration. Groups of male and female rats were exposed to OF vapor for a single duration (10, 60, or 240 min) in a whole-body dynamic chamber. Pupil diameter was measured by infrared camera technique. For six combinations of gender and exposure duration, effective concentration for miosis in 50% of exposed population and common probit slope were determined. Contrary to Haber's rule, ECt50 values increased with exposure duration. Female rats were more sensitive to GF vapor toxicity than male rats. Miosis was the only clinical sign noted following GF vapor exposure. Mydriasis was not observed in the present study. Depression of blood esterase (acetylcholinesterase, butyrylcholinesterase, and carboxylesterase) activities due to low level range of GF vapor concentrations was also investigated. Cyclosarin was regenerated from blood samples of vapor-exposed rats by addition of fluoride ion at pH 4, and the samples were analyzed by GC- FPD and GC-MS. Levels of regenerated GF in red blood cell fraction of samples were 5 to 40 times lower than in plasma. All controls were negative for regenerated GF.