Effects of Testosterone Replacement on Lower Urinary Tract Functions in Elderly Male Rats

Testosterone has been clinically used to improve hormone deficiency in the aging male; however, investigations how testosterone exerts its effects on lower urinary tract functions are not many. In order to shed light on the efficacy of testosterone on the functions, we replaced teststerone in elderly male Wistar rats aged 19 months. A relevant dose (120 mg) of testosterone was subcutaneously replaced through an implanted silastic tube into 6 rats for 4 weeks (treated group). Another 6 rats received no treatment for 4 weeks (control group). After the end of the 4-week period, we measured plasma testesterone, weight of bladder, prostate and body, bladder muscle content, spontaneous micturition behavior and cystometric parameters, and compared the results between the 2 groups. The daily micturition frequency (18.8 ± 1.5 times/day versus 15.5 ± 1.9 times/day), volume of residual urine at cystometry (0.66 ± 0.10 mL versus 0.24 ± 0.03 mL), bladder capacity (1.03 ± 0.06 mL versus 0.65 ± 0.05 mL), bladder weight (258 ± 9 mg versus 198 ± 19 mg), prostate weight (2.08 ± 0.22 g versus 1.29 ± 0.22 g) and ratio of smooth muscle area/connective tissue area (3.59 ± 0.13 versus 2.59 ± 0.36) were significantly higher in the treated group (P < 0.05). In contrast, the average volume of spontaneous micturition was significantly lower in the treated group (0.84 ± 0.07 mL versus 0.98 ± 0.09 mL). Differences in body weight and volume of 24-h urine were not significant between groups. Daily micturition frequency and volume of residual urine at cystometry were increased in the treated group. Testosterone replacement exerted unfavorable effects on the lower urinary functions of elderly rats, including prostatic hypertrophy.