Collagen content in the rat urinary bladder following removal of an experimental infravesical outlet obstruction.

A partial urethral obstruction was induced in female rats. After 6 weeks, detrusor weight had increased eightfold and collagen concentration had decreased to about 40% compared to controls. Due to the weight gain, the total amount of detrusor collagen had increased more than threefold. Removal of the obstruction led to a rapid decrease in detrusor weight to 70, 34 and 30%, 2, 4 and 6 weeks postobstruction, although control levels were not reached. Collagen content decreased more slowly than detrusor weight, and for the same groups was 97, 69 and 67% of the value in the obstructed detrusor. This led to a rapid increase in detrusor collagen concentration which already 4 weeks after removal of the obstruction had increased to a level that did not significantly differ from the control value. The discrepancy between decrease in detrusor weight and in collagen content after removal of the obstruction suggests that a large proportion of the collagen synthesized during the period of outlet obstruction remained. Changes in the ratio between muscle and nonmuscle tissue were limited between control, obstructed and nonobstructed bladders. This suggests that the collagen concentration following obstruction and removal of obstruction is to a large extent due to changes in collagen concentration in the interstitial connective tissue rich in collagen.