44 II. DIGESTION AND ABSORPTION OF FATS 



had no effect on cholinestera.se, nor did they reverse the effect of any of the 

 inhibitors studied. Cysteine was found to be an anti-inhibitor for the 

 /3-chlorinated amines. 



Both arsenical and non-arsenical vesicants have been proved by Thomp- 

 son 251 to be inhibitors of brain cholinesterase. When mustard gas or either 

 of two other nitrogen-containing vesicants was applied to the skin of rats, 

 cholinesterase activity was inhibited in the injured skin area. Moreover, 

 a significant reduction in .s-cholinesterase was observed in guinea pigs after 

 heavy contamination with mustard gas. It is suggested that some of the 

 systematic effects produced by certain of the vesicants may be due to the 

 inhibition of cholinesterase at the cholinergic nerve endings. 



Alcohols effect the hydrolysis of acetylcholine by rat brain in two differ- 

 ent ways. Fellowes and co-workers 252 demonstrated that activation 

 occurred at low concentrations. However, above the optimum concentra- 

 tion, the activation fell off rapidly, until complete inactivation occurred. 

 A maximal degree of activation resulted from n-butanol. Hydrolysis of 

 acetylcholine by serum cholinesterase (s-type) was found to be inhibited 

 bybutanol. 



(e) Cell Permeability in Relation to Cholinesterases. In addition to their 

 main function of destroying acetylcholine, cholinesterases bring about cer- 

 tain related reactions which are of importance. One of these, which has 

 been widely investigated, is the effect on cell permeability. Greig and 

 Holland 253 first pointed out that changes in the permeability of erythro- 

 cytes were produced by inhibition of the cholinesterase system, situated in 

 the cell membrane. Thus, it was shown that both methadon and eserine 

 produced changes in the permeability of dog erythrocytes. The effect of 

 drugs was shown to be influenced by the Na + and K + content of the me- 

 dium, by the pH, and by the presence of acetylcholine. Thus, according to 

 Holland and Greig, 254 when acetylcholine was added to a suspension of dog 

 erythrocytes in a medium containing potassium, there was a decrease in the 

 rate of swelling and in the permeability of the red blood cell to potassium. 

 The addition of eserine in an amount sufficient to inhibit the activity of 

 cholinesterase 60 to 80% resulted in a reversal of the permeability produced 

 by acetylcholine. A number of esters were shown to be effective in main- 

 taining the integrity of the red blood cell; these were, in decreasing order of 

 activity, the following: acetylcholine, triacetin, acetyl-(S-methylcholine, 



251 R. H. S. Thompson, J. Physiol, 105, 370-381 (1947). 



252 K. P. Fellowes, J. P. Rutland, and A. Todrick, Biochem. J., 47, xx (1950). 



253 M. E. Greig and W. C. Holland, Arch. Biochem., 28, 370-384 (1949). 

 »« W. C. Holland and M. E. Greig, Arch. Biochem., 26, 151-155 (1950). 



