Response of large intestinal mucosa in rats to dietary protein and fat
Lin, Hsi-chiang
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Permalink
https://hdl.handle.net/2142/20904
Description
Title
Response of large intestinal mucosa in rats to dietary protein and fat
Author(s)
Lin, Hsi-chiang
Issue Date
1990
Doctoral Committee Chair(s)
Baker, David H.
Department of Study
Nutritional Sciences
Discipline
Nutritional Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Biology, Animal Physiology
Agriculture, Animal Culture and Nutrition
Language
eng
Abstract
Epidemiological studies show that colon cancer incidence is correlated with meat consumption, and high fecal pH. Reported here are studies which examine the hypothesis that ammonia is produced in greater quantities in the large intestine of rats when high protein diets are fed and that increased rates of cell proliferation of the colon mucosa are associated with the diets high in protein and fat. The objectives of this research were: (1) to determine the pH and ammonia concentrations of the contents in the cecum and different segments of colon in rats fed defined semi-purified diets and (2) to determine if the pH and ammonia concentrations of the cecal and colon contents are associated with differences in mucosal cell proliferation of the cecum and colon.
Results of these studies showed the following: (1) Regional differences in dietary effects on intraluminal pH, ammonia concentration, water content and mucosal cell proliferation in the large intestine of rats. (2) High dietary protein significantly increased ammonia concentration along the large intestine, in vivo. (3) High dietary fat calories increased luminal pH in the colon of rats, in vivo. (4) Perfusion with ammonia containing solutions increased losses of mucus from the mucosal cells, increased DNA and carbohydrate losses into the perfusates, and produced damage to the mucosal epithelial cells. (5) Higher cell proliferative activities as measured by thymidine incorporation and ornithine decarboxylase (ODC) activity of mucosal cells in the distal colon were observed in rats consuming diets high in protein and fat calories.
It is concluded that ammonia arising from high protein intakes causes damage to mucosal cells which is followed by enhanced cell proliferation. Increased ODC activity and thymidine incorporation in the distal colon of rats fed high fat and protein diets is likely to result from high concentrations of unionized ammonia. Reassessment of the role of diet in colon cancer etiology should consider luminal pH, which influences ionization and concentration of the compounds in the colonic lumen which come into contact with mucosal cells.
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