Pancreas exocrine, proteins

Pancreatic secretion for many, if not most, species is regulated in order to insure adequate protein digestion. Correspondingly, protease inhibitors have a greater impact on pancreatic secretion than do inhibitors of amylase and lipase (Toskes, 1986). The secretory response of the exocrine pancreas to protease inhibitors can be rapid (< 10 min), does not involve parallel increases in the secretion of all enzymes (Holm et al., 1992), and is probably mediated by a signaling pathway (see below). 

As patients lose exocrine function of the pancreas, they have decreased ability to absorb lipids and protein ingested with normal dietary intake. Weight loss from nutritional malabsorption is a common symptom of chronic pancreatitis not often seen in acute pancreatitis. Fatty- or protein-containing stools are also common carbohydrate absorption is usually unaffected. Even though patients with chronic pancreatitis have decreased ability to absorb lipid from the gastrointestinal tract, there does not appear to be an increased incidence of fat-soluble vitamin deficiency in these patients.34... 

Denker SP, McCaffery JM, Palade GE, Insel PA, Farquhar MG (1996) Differential distribution of alpha subunits and beta gamma subunits of heterotrimeric G proteins on Golgi membranes of the exocrine pancreas. J Cell Biol 133 1027-1040... 

Exocrine pancreatic insufficiency is most commonly caused by cystic fibrosis, chronic pancreatitis, or pancreatic resection. When secretion of pancreatic enzymes falls below 10% of normal, fat and protein digestion is impaired and can lead to steatorrhea, azotorrhea, vitamin malabsorption, and weight loss. Pancreatic enzyme supplements, which contain a mixture of amylase, lipase, and proteases, are the mainstay of treatment for pancreatic enzyme insufficiency. Two major types of preparations in use are pancreatin and pancrelipase. Pancreatin is an alcohol-derived extract of hog pancreas with relatively low concentrations of lipase and proteolytic enzymes, whereas pancrelipase is an enriched preparation. On a per-weight basis, pancrelipase has approximately 12 times the lipolytic activity and more than 4 times the proteolytic activity of pancreatin. Consequently, pancreatin is no longer in common clinical use. Only pancrelipase is discussed here. 

Why this elaborate mechanism for getting active digestive enzymes into the gastrointestinal tract Synthesis of the enzymes as inactive precursors protects the exocrine cells from destructive proteolytic attack. The pancreas further protects itself against self-digestion by making a specific inhibitor, a protein called pancreatic trypsin inhibitor (p. 231), that effectively prevents... 

III. Recent Advances in the Chemical Characterization of Some Proteins of Exocrine Pancreas. 153... 

Although the whole problem of the stimulation of the exocrine pancreas is not discussed here for obvious reasons, it will be pointed out that it induces a relatively large protein output to which must correspond a very active protein biosynthesis. Cannulated steer pancreas for instance excretes... 

The acinar cells of pancreas synthesize, not only structural proteins and enzymes for their own metabolism, but also exocrine or exportable enzymes which are carried into the duodenum for digestive purposes. To this dual function corresponds a rather complicated system involving, besides biosynthesis itself, segregation, transport, storage, and final excretion. 

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