Impaired Na+/K+-ATPase Function in Patients with Interstitial Cystitis/Painful Bladder Syndrome

Na(+)/K(+)-ATPase (NKA) is abundantly expressed in the basolateral membrane of epithelial cells, which is necessary for tight junction formation. The tight junction is an urothelial barrier between urine and the underlying bladder. Impairment of tight junctions allows migration of urinary solutes in patients with interstitial cystitis/painful bladder syndrome (IC/PBS). We evaluated NKA expression and activity in bladder samples from patients with IC/PBS. The study group consisted of 85 patients with IC/PBS, and the control group consisted of 20 volunteers. Bladder biopsies were taken from both groups. We determined the expression and distribution of NKA using NKA activity assays, immunoblotting, immunohistochemical staining, and immunofluorescent staining. The protein levels and activity of NKA in the study group were significantly lower than the control group (1.08 ± 0.06 vs. 2.39 ± 0.29 and 0.60 ± 0.04 vs. 1.81 ± 0.18 µmol ADP/mg protein/hour, respectively; P < 0.05). Additionally, immunofluorescent staining for detection of CK7, a marker of the bladder urothelium, predominantly colocalized with NKA in patients in the study group. Our results demonstrated the expression and activity of NKA were decreased in bladder biopsies of patients with IC/PBS. These findings suggest that NKA function is impaired in the bladders from patients with IC/PBS.