THE BLADDER DOES NOT APPEAR TO HAVE A DYNAMIC SECRETED CONTINUOUS MUCOUS GEL LAYER
Abstract
Purpose:
We determined whether the nature of any protective barrier in the bladder is composed of a secreted mucous gel layer.
Materials and Methods:
We collected 24-hour urine samples for analysis from 8 healthy 22 to 49-year-old volunteers and 5, 19 to 59-year-old patients treated with bladder reconstruction, in addition to scrapings from 100 freshly slaughtered pig bladders. Samples were subjected to homogenization, dialysis, freeze-drying, papain digestion, gel chromatography, equilibrium density gradient centrifugation, periodic acid-Schiff assay and amino acid analysis. Normal human bladder, pig bladder, normal ileum and transposed intestinal segments were studied for the presence of a mucous layer using a new method of histological analysis.
Results:
Mucin content in normal urine is 2.7 mg/24 hours, meaning that less than 0.6% of nondialyzable material in normal urine is mucin. The mucin content of urine from reconstructed bladders amounted to 86 mg/24 hours (5.2% of nondialyzable material). We observed that glycosaminoglycans accounted for 41% of the peak total elution volume of PAS positive material in normal urine. Mucin estimation in urine can be grossly overestimated if contaminating glycoconjugates are not removed. Biochemical analysis of material scraped off the pig bladder surface demonstrated that the maximum thickness of a continuous layer that could be achieved was 13.6 μm. While we could visualize an obvious mucous layer on control ileal samples and biopsies of transposed ileal segments from patients with bladder reconstruction, we were unable to note a distinct, measurable mucous layer lining the bladder surface in humans or pigs.
Conclusions:
Mucin levels in normal human and pig urine would be enough for slow turnover of a thin barrier but the large increase in mucin in the urine of patients with transposed intestinal segments demonstrates that any layer in normal bladder is much different than that lining the transposed intestinal segment. The most likely constituents of this barrier are membrane bound rather than secreted mucins along with the proteoglycan components of the glycocalix.
References
- 1 : The morphology of normal human bladder urothelium. J Anat1989; 167: 103. Google Scholar
- 2 : A model for the function of glycosaminoglycans in the urinary tract. World J Urol1994; 12: 38. Google Scholar
- 3 : Mucin gene expression in human urothelium and in intestinal segments transposed into the urinary tract. J Urol2000; 164: 1398. Google Scholar
- 4 : A novel method for the visualization of the in situ mucus layer in rat and man. Clin Sci (Lond)1998; 95: 97. Google Scholar
- 5 : Mucous glycoproteins: a gel of a problem. Essays Biochem1985; 20: 40. Google Scholar
- 6 : Mucus glycoprotein content of human cholesterol gallstones. Digestion1987; 36: 132. Google Scholar
- 7 : Electrophoretic, chromatographic and immunological studies of human urinary proteins. Electrophoresis1995; 16: 124. Google Scholar
- 8 : Bladder surface glycosaminoglycans: an epithelial permeability barrier. J Urol1990; 143: 139. Link, Google Scholar
- 9 : A colorimetric assay for glycoproteins based on the periodic acid/Schiff stain[proceedings]. Biochem Soc Trans1978; 6: 607. Google Scholar
- 10 : A modified uronic acid carbazole reaction. Anal Biochem1962; 4: 330. Google Scholar
- 11 : Characterization of gastric mucoproteins isolated by equilibrium density-gradient centrifugation in caesium chloride. Biochem J1974; 141: 633. Google Scholar
- 12 :
Simple, economical amino acid analysis based on pre-column derivativization with 9-Fluorenylmethyl Chloroformate (FMOC) . In: Techniques in Protein Chemistry. Edited by . San Diego: Academic Press1989: 266. Google Scholar - 13 : Mechanical characterization and properties of gastrointestinal mucus gel. Biorheology1987; 24: 615. Google Scholar
- 14 : Reducing mucus production after urinary reconstruction: a prospective randomized trial. J Urol2001; 165: 1433. Link, Google Scholar
- 15 : Secreto-motor function of intestinal segments used in lower urinary tract reconstruction. Br J Urol1987; 60: 532. Google Scholar
- 16 : Characterization of pig colonic mucins. Biochem J1996; 316: 937. Google Scholar
- 17 : Studies on the “insoluble” glycoprotein complex from human colon. Identification of reduction-insensitive MUC2 oligomers and C-terminal cleavage. J Biol Chem1999; 274: 15828. Google Scholar
- 18 : Culture of human middle ear mucosal explants; mucin production. Clin Otolaryngol1992; 17: 491. Google Scholar
- 19 : Properties of gastric and duodenal mucus: effect of proteolysis, disulfide reduction, bile, acid, ethanol, and hypertonicity on mucus gel structure. Gastroenterology1985; 88: 269. Google Scholar
- 20 : The bladder mucus (glycosaminoglycan) layer in interstitial cystitis. J Urol1993; 149: 716. Link, Google Scholar
- 21 : The gastroduodenal mucus barrier and its role in protection against luminal pepsins: the effect of 16,16-dimethyl prostaglandin E2, carbopol-polyacrylate, sucralfate and bismuth subsalicylate. J Gastroenterol Hepatol1994; 9: S55. Google Scholar
- 22 : Epithelial mucin genes. Annu Rev Physiol1995; 57: 607. Google Scholar
- 23 :
Gastrointestinal mucus . In: . Edited by . Bethesda, Maryland: American Physiological Society1989: 359. Google Scholar - 24 : Soluble and insoluble mucins—identification of distinct populations. Biochem Soc Trans1995; 23: 845. Google Scholar
Academic Urology Unit, University of Aberdeen (JN′D), Aberdeen, Scotland, and Departments of Surgery and Physiological Sciences, Medical School, University of Newcastle upon Tyne (NJ, CNR, JPP), Newcastle upon Tyne and Department of Surgical Oncology, Addenbrooke’s Hospital, Cambridge University (DEN), Cambridge, England, United Kingdom
