OBJECTIVE Recent evidence indicates that ischemia and reperfusion (free radical generation) are major etiologic factors in the rabbit bladder subjected to partial outlet obstruction. The current investigation was designed to determine the time course of damage caused by reactive oxygen species (ROS) and reactive nitrogen species (RNS) by measuring the carbonyl and nitrotyrosine content of the bladder. METHODS Male rabbits underwent surgical partial bladder outlet obstruction for durations of 1, 2, 4, and 8 weeks. Sham-operated rabbits served as controls. The contractile responses to field stimulation (32 Hz) and carbachol (20 micromol/L) were determined. The nerve density was determined by using immunohistochemical methods. The carbonyl and nitrotyrosine contents within the bladder body wall and mucosa were analyzed by Western blotting. RESULTS Nerve density showed marked decrease in obstructed bladders. The responses to field stimulation and carbachol showed remarkable decrease in bladders after 8 weeks' obstruction. The protein carbonylation increased significantly in obstructed bladders when compared with controls, both in mucosa and muscles and reached the highest level in 4 weeks' obstruction. There was a 2-fold increase for nitrotyrosine in mucosa after 8 weeks of obstruction. The increased expression of nitrotyrosine in muscle was maximized at 4 weeks of obstruction. CONCLUSIONS The free radicals mediated protein carbonylation and tyrosine nitration occurs to a significant degree in the partially obstructed rabbit bladder. This may be related with sensory and contractile dysfunction and can be used as markers for free radical damage and reperfusion injury.