Nonbactierial prostatitis caused by partial urethral obstruction in the rat

The pathogenesis of nonbacterial prostatitis (NBP) is not understood mainly due to the lack of appropriate experimental models. We developed a new exp erimental model of NBP by inducing a partial obstruction of the urethra (PU O) in the rat. Male Wistar rats aged 12 weeks were used. PUO was produced b y a nylon ligature on the urethra over a rubber tube, The tube was slipped out after the ligature had been tied. Two rats were examined histologically 6 h, 1 day, 3 days and 7 days after PUO. In another group, two rats were k illed at 1, 3 and 7 days after the release of the PUO that had been left in place for 3 days. On day 3, another eight rats with PUO and eight control rats had 2 ml of urine in the bladder replaced by the same volume of lucife r yellow (LY; 10 mu g/ml, MW 500), microperoxidase (MP; 20 mu g/ml, MW 1900 ), horseradish peroxidase (HRP; 10 mu g/ml, MW 40 000), or saline as contro l, respectively. Lymphocytic infiltration and interstitial edema were noted in the prostate following PUO, being most prominent on day 3. After the re lease of the PUO, these inflammatory changes gradually disappeared. Only LU was noted within the prostatic stroma of the rats 2 h after bladder instil lation. Intraprostatic urinary reflux may be an etiologic factor in NBP. Th e present study showed that lower urinary tract obstruction caused NBP in t he rat. Penetration of prostatic tissue by low-molecular-weight substances in the urine may trigger NBP.