Protein digestion and absorption in rats with pancreatic duct occlusion

The effects of pancreatic duct ligation on the digestion and absorption of a randomly 14C-labeled protein meal has been investigated in the rat. Although there was a significant reduction in luminal digestion and absorption of the protein meal in the pancreatic duct-ligated animals compared with controls, 37% of administered protein was absorbed despite absence of luminal pancreatic proteolytic enzyme activity. To characterize further the digestive and absorptive processes that occur in the absence of luminal pancreatic proteolytic enzyme activity, whole protein meal (untreated) and protein preincubated with (1) pepsin and HCl, and (2) HCl alone (treated), was instilled into isolated loops of rat intestine containing no demonstrable pancreatic proteolytic enzyme activity. Thirty per cent absorption of the untreated protein meal occurred in 4 hr; significantly greater amounts of both treated forms of meal were absorbed. It is concluded that the small bowel has the capacity to hydrolyze and absorb nutritionally significant amounts of dietary large molecular weight protein in the absence of luminal pancreatic enzyme activity. Furthermore, this process may be enhanced by prior denaturation and proteolysis in the stomach.