Detrusor dysfunction secondary to partial outflow obstruction is caused in part by decreased blood flow to the detrusor. We investigated changes in blood flow to the bladder and in bladder function after inducing partial outflow obstruction. The urethras of male Sprague-Dawley rats were constricted by sutures to degrees representing either mild and severe obstruction. Blood flow to the bladder was measured by a Doppler flowmeter prior to and 7 days after obstruction. In vivo and in vitro experiments were performed 7 days after surgery. After cystometry was used to determine bladder capacity, the pressure at which micturition was induced, and maximum voiding pressure, the bladder was removed and placed in an organ bath where increases in intravesical pressure in response to field stimulation were evaluated. Finally, volume-pressure studies were performed in order to determine passive detrusor compliance and response to field stimulation at each specific capacity in vitro. Although blood flow to the bladder was significantly decreased by severe obstruction, no differences in blood flow between control and mildly obstructed bladders was observed. While maximum voiding pressure decreased in severely obstructed bladders, both the pressure at which micturition was induced and bladder capacity were increased. The response to field stimulation was increased by mild obstruction but decreased by severe obstruction, although bladder compliance was increased by both. The peak response to filled stimulation was observed at a larger capacity in severely obstructed bladders than the others. In conclusion, when outflow obstruction was mild, blood flow to the bladder remained unchanged and detrusor contractility increased. On the other hand, severe obstruction decreased bladder blood flow and induced deterioration of detrusor function.
Background: Acute ethanol ingestion increases the risk of urinary retention in patients with benign prostatic hyperplasia (BPH). To elucidate the mechanism of this effect, we investigated the in vitro effects of ethanol on lower urinary tract function in rabbits. Methods:The responses to various stimuli of muscle strips isolated from male rabbit bladder and urethra were determined in the presence of O%, 0.5%, 1 .O%, and 3.0% ethanol.Results: Basal tension of tissue strips taken from the bladder and the urethra was reduced by ethanol in a dose-dependent manner, as were bladder contractions induced by field stimulation, bethanechol, and ATP. Ethanol also reduced phenylephrine-induced contractions of the prostatic urethra. A high (3%) concentration of ethanol significantly reduced KCI-induced contraction of both the bladder and urethra, as well as urethral relaxation induced by field stimulation following contraction with 200pmol/L phenylephrine. Conclusion: Responsiveness of the rabbit lower urinary tract was significantly reduced by exposure to ethanol. A similar decrease in tonus and contractility of the detrusor and inhibition of relaxation in the prostatic urethra may lead to urinary retention in men following acute ingestion of ethanol.
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