Mast cell activation and response to tolterodine in the rat urinary bladder in a chronic model of intravesical protamine sulfate and bacterial endotoxin-induced cystitis.

The aim of the present study was to use an animal model of interstitial cystitis (IC) in order to investigate the histology and function of the bladder, with a particular focus on mast cell degranulation and response to detrusor overactivity (DO) to tolterodine. A total of 18 female Sprague-Dawley rats were used. In 12 rats, lipopolysaccharide (LPS) was intravesically instilled following the induction of IC by protamine sulfate (PS) and six rats were subjected to sham instillations. Following 1 month, cystometry was performed. The effects of tolterodine were tested in half of the animals with IC. All rats in the IC group demonstrated DO during the filling phase and no significant changes in the frequency or pressure compared with that following tolterodine injection were identified. Histological examination revealed a significant increase in the total number of infiltrated mast cells in IC rats compared with that in the sham rats (P<0.05). Degranulated mast cells were evident in 80% of rats with IC; however, they were not apparent in the sham rats. Urinary bladder inflammation, similar to that in human IC in terms of degranulated mast cells and bladder function, was induced in rats. The animal model used in the present study provided insight into the pathophysiological mechanisms underlying the ineffectiveness of anticholinergics in patients with overlapping IC and overactive bladder (OAB).