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

Abstract

To determine whether interstitial cystitis is associated with the increased release of substance P from the bladder wall into urine, by measuring urinary excretion rates of substance P and its metabolites in women with interstitial cystitis and in a control group of women with stress incontinence and normal bladder function. Catheter urine was collected from 13 patients and 10 controls during a water diuresis ( approximately 10 mL/min) before and after instilling the bladder with 100 mL of water. The contribution of the bladder wall to urinary substance P peptides was assessed by measuring the change in substance P peptide levels after 2 min of bladder stasis before and after instillation. Absolute substance P excretion rates were similar in patients with interstitial cystitis and controls; 2 min of bladder stasis reduced the substance P excretion rate (P = 0.03) and increased the excretion rate of substance P metabolites (P = 0.01). The release of substance P from the bladder wall was not increased in patients with interstitial cystitis.