BODANSKY: CHOLINESTERASE 



535 



occurred at the higher exposures; at lower exposures, no symptoms ex- 

 cept miosis occurred. In most instances, the decrease in red blood cell 

 cholinesterase activity was greater than that in serum eholinesterase 

 activity. It will be recalled that in vitro rabbit red cell cholinesterase 

 is more sensitive than serum cholinesterase to inhibition by DFP. 

 When rhesus monkeys were exposed to DFP, the plasma cholinesterase 

 activity was decreased to only 1 to 5 per cent of normal, at almost all 

 exposures, whereas the red cell cholinesterase activity showed only 

 slight decreases at the lower exposures. This marked difference in the 

 extent of decrease paralleled the considerable in vitro difference be- 

 tween the sensitivities of monkey red cell and serum cholinesterases to 

 inhibition by DFP. 



The effect of intravenously injected DFP on cholinesterase activity, 

 in the rabbit, is shown in table 7. It can be seen that, in most in- 



Table 7 



The Effect of Intravenously Injected Diisopropyl-Fluorophosphate on Rabbit 

 Plasma, Red Cells, and Brain Cholinesterase Activity In Vivo 



* These values are per cent of the pre-exposure values. 



stances, the red cell cholinesterase activity is more markedly reduced 

 than that of the serum cholinesterase. This difference corresponds to 

 the in vitro difference in sensitivities. The brain cholinesterase activ- 

 ities were reduced to about the same extent as the serum cholinesterase 

 activities at the lower doses, and slightly less at the higher doses. This 

 finding did not correspond to the in vitro sensitivity of brain cholin- 

 esterase to inhibition by DFP. The brain cholinesterase activities, 

 corresponding to the appearance of symptoms, were less than about 60 

 per cent of normal. 



The effect of intravenous injections of DFP in the monkey are shown 

 in TABLE 8. A dose of 0.3 mg. per kg. was fatal in 10 minutes. The 

 serum, red blood cell, and brain cholinesterases were reduced to very 



