| Abstract: | Experiments were performed to determine whether the low compliance seen in the bladders of guinea pigs with a partial bladder outflow obstruction was due to active or passive properties of the bladder wall. Sham-operated and obstructed animals were assessed urodynamically 6 to 12 weeks later. Three-quarters of the obstructed animals had developed low-compliance bladders. In vitro cystometry was performed on the isolated bladders in a physiological saline solution. The measurements were then repeated in Ca-free solution to abolish any contribution of smooth muscle contraction, and then in a high K, Ca-containing solution, which initiates maximum contraction in isolated detrusor strips. Bladder compliance was higher in the sham-operated animals than in obstructed animals. In sham-operated animals the compliance was decreased in the high K solution, but in the obstructed, low-compliance bladders the compliance did not change significantly under any experimental condition, suggesting that in this latter group the low compliance was caused by passive properties of the bladder wall. Changes in the viscosity of the bladder wall were assessed by monitoring the decline in pressure after a stepwise increase in bladder volume. No change in the viscosity of the obstructed bladder was detected. We conclude that the low compliance in the obstructed guinea pig is probably due to a change in the elasticity of the bladder wall. |
