In the absence of overt urothelial damage, chondroitinase ABC digestion of the GAG layer increases bladder permeability in ovariectomized female rats. Am J Physiol Renal Physiol 310: F1074 -F1080, 2016. First published February 24, 2016 doi:10.1152/ajprenal.00566.2015.-Loss of integrity of the protective impermeability barrier in the urothelium has been identified as significant in bladder dysfunction. In this study, we tested the theory that the luminal layer of glycosaminoglycans (GAG) serves as an important component of barrier function. The peptide polycation protamine sulfate (PS), 1 mg/ml, was instilled intravesically for 10 min into rat bladders. Chondroitinase ABC (ChABC), 63 IU/ml, was instilled into an additional six rats for 30 min to digest the GAG layer. Unmanipulated controls and sham-injected controls were also performed. After 24 h, the rats were euthanized, the bladders were removed, and permeability was assessed in the Ussing chamber and by diffusion of FITC-labeled dextran (4 kDa) to measure macromolecular permeability. The status of tight junctions was assessed by immunofluorescence and electron microscopy. In control and sham treated rat bladders, the transepithelial electrical resistance were means of 2.5 Ϯ 1.1 vs. 2.6 Ϯ 1.1 vs 1.2 Ϯ 0.5 and 1.01 Ϯ 0.7 k⍀·cm 2 in the PS-treated and ChABC-treated rat bladders (P ϭ 0.0016 and P ϭ 0.0039, respectively). Similar differences were seen in dextran permeability. Histopathology showed a mild inflammation following PS treatment, but the ChABC-treated bladders were indistinguishable from controls. Tight junctions generally remained intact. ChABC digestion alone induced bladder permeability, confirming the importance of the GAG layer to bladder barrier function and supports that loss of the GAG layer seen in bladder biopsies of interstitial cystitis patients could be a significant factor producing symptoms for at least some interstitial cystitis/painful bladder syndrome patients. urinary bladder; administration; intravesical; cystitis; interstitial; permeability; models; animal INTERSTITIAL CYSTITIS (IC) is a disease of the bladder diagnosed by exclusion on the basis of urgency, frequency, and pain (6). Although the etiology of this disease remains unknown, the evidence suggests that there is disruption of the urothelium that could result in enhanced bladder permeability (9,17,22,31). For the IC patient, the presence of urine is responsible for inflammation and pain in addition to promoting thinning and sloughing of the urothelium and distinct changes in the muscle (21,27,30). A high proportion of IC patients show loss of chondroitin sulfate from the luminal surface of the urothelium as well as abnormalities in uroplakin, the cell adherence protein E-cadherin, and ZO-1, the molecule in the zona occludens that links cells together (9). The identification of comorbitities that appear frequently with IC has suggested that the bladder symptoms are part of a wider spectrum of symptoms denoted by chronic pelvic pain (CPP) or IC/painful bladder syndrome (IC/...