410 IMMUNO-CATALYSIS 



note that the enzyme 1-histidine decarboxylase is inhibited by adren- 

 aline and arterenol (Werle, 1942) which exercise antihistamine effects. 

 Holtz, et ah (1938) reported the presence of 1-histidine decarboxylase 

 in the wall of the small intestine, but not that of the colon and rectum, 

 of the guinea pig. Since the fetal guinea pig intestine also formed 

 histamine from 1-histidine, the formation of histamine in the intestinal 

 wall of the adult animal is most likely not due to bacterial activity 

 (Holtz, Credner, and Reinhold, 1939). These observations strongly 

 suggest the presence of an 1-histidine decarboxylase in mammalian 

 tissues. The amounts of histamine formed, in in vitro experiments are 

 small. It has not been isolated, but rather characterized pharmacolog- 

 ically. On the isolated guinea pig small intestine, the extracts caused 

 contraction of the muscle which was not abolished by atropine; and 

 when the muscle had become specifically insensitive to histamine by 

 its administration in large doses the extracts were found to be inactive 

 (Werle and Hermann, 1937). This effect is considered typical for 

 histamine (Barsoum and Gaddum, 1935). 



The question of an exclusive source of total histamine in the animal 

 system cannot be answered. Both the 1-histidine decarboxylases of 

 animal tissues and of intestinal bacteria may be contributory in this 

 respect. Histamine can readily form from 1-histidine by the action of 

 micro-organisms normally present in the intestinal tract. This mecha- 

 nism could account for the formation of histamine in the intestine. 

 Ackermann (1910) reported that putrefactive bacteria could produce 

 histamine from histidine by a process of decarboxylation. And Mel- 

 lanby and Twort (1912) observed that normal organisms of the 

 intestinal tract of man and animals could likewise produce histamine, 

 and that the latter is a regular constituent of the intestinal content 

 and feces. Gale (1946) reported that E. coli and related organisms, 

 nine of 10 strains of CI. welchii type A, strains of CI. welchii types B, 

 C and D, and one of two strains of CI. fallax possessed histidine decar- 

 boxylases. He studied E. coli amino acid decarboxylases extensively. It 

 is therefore reasonable to suggest that histamine formed by intestinal 

 bacteria could readily diffuse through the intestinal wall and be 

 stored in various tissues, in a manner similar to the storage and utiliza- 

 tion by the animal system of essential vitamins synthesized by intestinal 

 Hora. 



