Urinary and bladder responses to immobilization in male rats

Immobilization of groups of five to nine male rats for 2–5 days results in a 50% increase in urinary bladder fresh weight compared with normally caged controls. The increase in urinary bladder weight was not due to tissue oedema and was accompanied by epithelial hyperplasia in some urinary bladders. Immobilization did not alter total urine volume, but it did decrease the frequency of urine voiding and doubled the mean urine weight/voiding. Thus, bladder distention caused by the increased volume per voiding caused a rapidly induced increase in bladder tissue growth, and was accompanied by an increase in bladder epithelial cell division.