126 KINETIC HORMONES — II 



Digestive enzyrne secretion by the duodenum 



Mammalia. There is some evidence (Grossman, 1950) for 

 DUOCRININ being secreted like secretin, from the mucosa of the 

 duodenum in response to acid, but it acts upon Brunner's glands 

 in the wall of the duodenum itself and not upon the pancreas. It 

 appears with secretin in crude extracts of the mucosa, but is 

 separable from it. 



Digestive enzyme secretion by the intestine 



Mammalia. Certain peptones in contact with the intestinal 

 wall stimulate the secretion of enterocrinin, which increases the 

 succus entericus, both in volume and in enzyme content. The gland 

 cells that secrete the succus entericus are in the walls of the 

 jejunum and ileum. The cells that secrete enterocrinin are con- 

 fined to the same region of the intestine, but have not been identi- 

 fied histologically. 



4.112 Decrease in secretion by gut glands 



A number of hormones have been postulated as having an 

 inhibiting effect upon the exocrine glands of the mammalian gut ; 

 but such an action is difficult to prove because so many factors in 

 the experimental procedures are liable to reduce either the activity 

 of the gland or the sensitivity of the tissues at one point or another 

 in the chain between the gut surface, the endocrine cells and the 

 exocrine glands. 



Inhibition of acid secretion by stomach glands 



Mammalia. The most clearly established of the inhibiting 

 hormones is enterogastrone. Its source, like that of some stimu- 

 lating hormones, is in the duodenal mucosa; but its action is to 

 counteract that of gastrin and to inhibit the secretion of acid by 

 the gastric glands, thereby bringing to an end the gastric phase of 

 digestion and facilitating the neutralization of the gut contents 

 as they pass into the duodenum (Fig. 4-1). 



"Among the agents which inhibit gastric secretion when present 

 in the duodenum, fat is the only one which has been proven by 

 experiments with the transplanted pouch to act by release of 



