Permeability of intestinal mucosa from urinary reservoirs in man and rat.

OBJECTIVE: To evaluate the barrier properties of intestinal mucosa chronically exposed to urine and to evaluate possible differences between ileal and colonic segments used in the reconstruction of the urinary tract. MATERIALS AND METHODS: Mucosal specimens from patients with continent reservoirs with an abdominal stoma, or orthotopic neobladders constructed from colonic segments, were obtained at revisional surgery. Control segments were obtained during right-sided hemicolectomy. In addition, ileal and colonic segments from enterocystoplasties in rats were assessed. The mucosa-to-serosa passage of marker molecules, i.e. (14)C-mannitol, (3)H-glucose, fluorescein isothiocyanate-dextran 4400 and ovalbumin, was measured using modified Ussing diffusion chambers. RESULTS: In man, there were no permeability differences between segments exposed to urine and control segments for any of the marker molecules. In rats, there was less passage of markers in ileal and colonic transplanted segments than in intestinal segments from sham-operated animals. CONCLUSIONS: Intestinal mucosa that has been in chronic contact with urine maintains its barrier function; in the rat model the permeability was even decreased. In addition, there were no detectable differences between ileal and colonic segments in this model.

Intestinal permeability in humans is increased after radiation therapy.

PURPOSE: Irradiation inflicts acute injuries to the intestinal mucosa with rapid apoptosis induction and subsequent reduction in epithelial surface area. It may therefore be assumed that the intestinal barrier function is affected. The aim of this study was to compare the mucosal permeability in irradiated rectum and nonirradiated sigmoid colon from patients subjected to radiation therapy before surgical treatment for rectal cancer. METHODS: Segments from sigmoid colon and rectum obtained from irradiated and nonirradiated patients were stripped from the serosa-muscle layer and mounted in Ussing diffusion chambers. The mucosa-to-serosa passage of the marker molecules 14C-mannitol, fluorescein isothiocyanate-dextran 4,400, and ovalbumin was followed for 120 minutes. RESULTS: The permeability to the markers was size-dependent and increased linearly across time in all specimens. The passage of all markers was increased in irradiated rectum compared with nonirradiated sigmoid colon, whereas in specimens from nonirradiated patients there were no differences between rectum and sigmoid colon. Histologic signs of crypt and mucosal atrophy were found in the irradiated rectal specimens. CONCLUSIONS: Early gastrointestinal complications after radiation therapy may be the result of mucosal atrophy in addition to mucosal damage, with a loss of barrier integrity.

Mucosal in vitro permeability in the intestinal tract of the pig, the rat, and man: species- and region-related differences.

BACKGROUND: The barrier properties of the gastrointestinal mucosa may be studied by measuring its permeability to different-sized marker molecules. Owing to difficulties in obtaining human tissue it is, however, often necessary to extrapolate findings from experimental animals to man. The aim of the present study was to compare regional intestinal mucosal permeability in man, the rat, and the pig, using the same marker molecules and in vitro technique. METHODS: Segments from jejunum, ileum, colon, and rectum were mounted in Ussing diffusion chambers, and the mucosa-to-serosa passage of 14C-mannitol, fluorescein isothiocyanate (FITC)-dextran 4,400, alpha-lactalbumin, ovalbumin, and FITC-dextran 70,000 was studied. RESULTS: Irrespective of species or intestinal region an inverse relationship between the molecular weight of the markers and the permeability was seen. The mannitol permeability was higher in the small intestine than in the colon in man, whereas the rat showed a higher permeability in the ileum than in the jejunum and colon. The FITC-dextran 4,400 permeability was higher in all intestinal regions in the rat than in man and the pig. The macromolecules showed low permeability with no regional differences. CONCLUSIONS: The results showed differences between intestinal regions and between species. Permeability data from the pig correlated fairly well with those of man, whereas the rat differed, making it difficult to extrapolate from the rat to man.

Increased colonic permeability in patients with ulcerative colitis: an in vitro study.

BACKGROUND: Colonic permeability was studied in vitro in patients subjected to colectomy because of ulcerative colitis and in control patients undergoing colonic resections for cancer. METHODS: The mucosal layer from fresh colonic segments was stripped and mounted in Ussing diffusion chambers containing modified Krebs buffer solution. The mucosa to serosa passage of the marker molecules 14C-mannitol and ovalbumin was measured for 120 min. RESULTS: Marker passage was significantly increased in colitis patients compared with control patients, irrespective of age, sex, duration of disease, and treatment. Marker passage was further increased in patients with acute colitis. The increased colonic permeability may be explained by inflammation and the resultant loss of mucosal integrity. The increased permeability to ovalbumin implies that permeability to luminal macromolecules, such as bacterial products and other antigenic substances, might be increased in colitis. CONCLUSIONS: The results suggest a derangement of the colonic barrier, as evidenced by an increased mucosal permeability in both chronic and acute colitis.