Short term functional effects of bladder outlet obstruction in the cat

Experimental bladder outlet obstruction in cats was produced by surgical placement of a silastic cuff around the urethra. Two sizes of cuff were used to produce either moderate or severe obstruction. The following is a summary of the short-term effects on bladder function. Obstruction induced a significant increase in the in vivo voiding pressure, in proportion to severity of the obstruction. There were no significant differences between control and obstructed cats in bladder mass, response of the isolated whole bladder to field stimulation or bethanechol, response of isolated bladder strips to field stimulation, bethanechol and ATP, or muscarinic receptor density in the bladder body. Although there were no differences in bladder mass between control and obstructed bladders, the hydroxyproline concentration of the severely obstructed bladders was significantly reduced. Creatine phosphate concentration was also significantly reduced in obstructed bladders. Although all whole cat bladder preparations displayed spontaneous contractile activity during in vitro cystometry, the obstructed bladders had a greater amplitude and frequency of spontaneous contractions with a lower volume threshold. In addition, the obstructed bladders had a greater tetrodotoxin-resistant contractile response to field stimulation. These results suggest that the obstructed cat bladder can compensate for increased outlet resistance without induction of bladder hypertrophy or significant functional changes, as seen in both rat and rabbit.