Altered inducible nitric oxide synthase expression and nitric oxide production in the bladder of cats with feline interstitial cystitis

Purpose: Alterations in nitric oxide (NO) levels have been demonstrated in some humans with interstitial cystitis (IC) as well as in chemically induced animal models of cystitis. Thus, in the current study we investigated whether inducible NO synthase (iNOS) mediated NO production is altered in the bladder of cats with a naturally occurring model of IC termed feline IC (FIC). Materials and Methods: We examined iNOS expression using Western immunoblotting and baseline NO production using an NO microsensor from smooth muscle and mucosal bladder strips in 9 healthy cats and 6 diagnosed with FIC. Results: There was a significant increase in baseline NO production in cats with FIC compared with that in healthy cats in smooth muscle and mucosal strips. This production was not ablated in the absence of extracellular Ca2+ (100 muM egtazic acid) or following incubation with the calmodulin antagonist trifluoroperazine (20 muM), indicating iNOS mediated Ca2+ independent NO production. Release was significantly decreased following incubation with the NOS antagonist L-NAME (N-nitro-L-arginine methyl ester) (100 muM). Furthermore.. immunoblotting revealed a trend toward increased iNOS expression in smooth muscle and mucosal strips from FIC cats but not from healthy cats. Conclusions: In light of previous findings that the barrier property of the urothelial surface is disrupted in FIC and iNOS mediated increase in NO alters barrier function in other types of epithelium our findings suggest that iNOS dependent NO production may have a role in epithelial barrier dysfunction in FIC.