Stretch Behavior of the Bladder as an Approach to Vascular Distensibility

Abstract

Volume injections were made into kitten bladders, following the pressure changes as related to time. A time-dependent factor influencing wall tension was clear, so that peak tension and hysteresis loop width decreased with successive, equal stretches. Rate of tension decline (decay) at fixed stretched length varied non-linearly with time, and was related to the starting (end-stretch) tension level but not to the actual length. After killing with NaCN, the bladder still showed the same relation of decay rate to initial tension. The dead bladder showed a decreased distensibility, related to the poor rate of tension recovery between stretches. The living bladder showed a direct relation between the tension values during a stretch and the rate of that stretch. This rate- dependency was less marked after death. With successive stretches, the rate-dependency became smaller and effectively disappeared. When stimulated electrically, a small and brief tension rise was seen. Except when tension was actually rising because of contraction, elasticity of the living bladder could not be shown to be altered by muscle activity.