Urinary levels of substance P and its metabolites are not increased in interstitial cystitis

Objectives To determine whether interstitial cystitis is associated with th e increased release of substance P from the bladder wall into urine, by mea suring urinary excretion rates of substance P and its metabolites in women with interstitial cystitis and in a control group of women with stress inco ntinence and normal bladder function. Patients and methods Catheter urine was collected from 13 patients and 10 c ontrols during a water diuresis (approximate to 10 mL/min) before and after instilling the bladder with 100 mt of water. The contribution of the bladd er wall to urinary substance P peptides was assessed by measuring the chang e in substance P peptide levels after 2 min of bladder stasis before and af ter instillation, Results Absolute substance P excretion rates were similar in patients with interstitial cystitis and controls; 2 min of bladder stasis reduced the sub stance P excretion rate (P = 0.03) and increased the excretion rate of subs tance P metabolites (P = 0.01). Conclusions The release of substance P from the bladder wall was not increa sed in patients with interstitial cystitis.