Effect of acid secretory capacity and chronic endogenous hypergastrinemia on pancreatic secretion and intestinal morphology in the rat

Growth factors and intestinal neoplasms

Signals that control normal and neoplastic epithelial proliferation are not completely understood. We have reviewed the importance of the possible roles of the following control mechanisms: polyamine biosynthesis, intraluminal nutrients, gastrointestinal hormones and growth factors, bowel resection, carcinogens, and oncogenes. The mechanisms by which these agents act and the precise roles they play in normal and abnormal proliferation of intestinal mucosa have not yet been clearly defined. Peptide hormones and growth factors exert their mitogenic effects by first interacting with specific receptors in the cell membrane. Oncogenes induce production of growth factors or replace growth factors and, by themselves, stimulate growth. We believe that no single agent is likely to be responsible; rather, multiple agents are involved in stimulation of growth of normal and neoplastic intestinal epithelial cells. A clear understanding of the factors responsible for regulation of normal and abnormal intestinal cell growth will greatly facilitate the development of therapeutic strategies for the prevention and treatment of gastrointestinal cancers.

Cimetidine and neonatal small bowel adaptation: an experimental study

Histamine2-blockers are being used more extensively in the pediatric short gut patient as an agent to accelerate small bowel adaptation. Reversal of lipid malabsorption and a direct trophic effect on the intestinal crypt cells have been postulated as the mechanism for the salutary influence of cimetidine. Weanling Sprague-Dawley rats underwent 85% small bowel resection. Controls had repair of a simple ileal transection. Rats received either a fat-defined rat chow only, or chow with high- or low-dose cimetidine, 2% cholestyramine, or cholestyramine/low-dose cimetidine. All animals were killed 2 weeks postresection, and ileal and jejunal sections were examined for changes in villous and crypt morphology. The animals receiving cimetidine showed earlier and more consistent weight gain than resected animals who received no adjunctive treatment. High- and low-dose regimens were equally efficacious. Cimetidine administered alone decreased fecal fat losses, but not when given with cholestyramine. The cimetidine/cholestyramine group showed increased weight gain when referenced to the resection controls despite continuing lipid malabsorption. Villous and crypt lengthening did not correlate with clinical evidence of adaptation. An augmented lymphocytic activity (plasma cell hyperplasia, enlargement Peyer's patches) was present in the hyperplastic ileal segments of the cimetidine-treated rats. Overall immunoreactivity was similar in all study groups. No significant differences in villous morphology or immunologic activity were seen in jejunal segments. The effects of H2-blockers on lipid absorption and intestinal hyperplasia are inadequate to explain the benefits of cimetidine in the short gut patient. Examination of the immunology of the short bowel complex merits further attention in elucidating cimetidine's action in this setting.

Rat exocrine pancreas following total gastrectomy

Sixteen rats underwent a total gastrectomy with an end-to-end anastomosis between the esophagus and duodenum. After either two or four weeks, the entire pancreas was excised and isolated lobules were incubated for 60 min in Krebs-Ringer-Hepes solution either with or without addition of ceruletide (5 X 10(-10) g/ml). Amylase was determined every 15 min in the supernatant medium. Measurements of amylase, lipase, trypsin, DNA and total protein were carried out in the homogenized pancreatic tissue. Morphometry was performed via light microscopic analysis. Two weeks following gastrectomy there was an increase in pancreatic wet weight, DNA, total protein and enzyme content (except lipase). Four weeks after surgery, pancreatic weight, amylase and trypsin increased further, whereas DNA content and lipase content remained stable. The DNA concentration decreased, and the size of exocrine pancreatic cells increased. In vitro, amylase discharge increased only after four weeks. The experiments demonstrate a short-term adaptation of the rat exocrine pancreas following total gastrectomy in the form of cellular hyperplasia (after 2 weeks), and hypertrophy (after 4 weeks), and enzyme dissociation.