Responses of detrusor smooth muscle to stretch and relaxation: in vitro study.

An in vitro model subjecting bladder muscle strips to continuous stretch relaxation evaluated-the properties of passive muscle length and tension. Tension generated as a strip was stretched or relaxed was found to be stretch-rate dependent. The primary influence of stretch rate on muscle tension is by alteration of muscle length; however, stretch and relaxation rates do influence the inherent smooth muscle properties of hysteresis, stress-relaxation, and adaptation. The characteristic filling curve to the point of bladder contraction seen clinically during cystometry in the neurologically intact subject can be reproduced in isolated bladder muscle strips. The bladder function of storage is a result of passive smooth muscle properties of muscle length and tension which can, however, be altered by superimposed neurologic influences.