Collagen content in the rat urinary bladder subjected to infravesical outflow obstruction

Collagen content was determined in the detrusor muscle from control rats and rats subjected to infravesical outflow obstruction for periods of 3 days to 4 months. During the 1st 6 weeks of obstruction the detrusor weight increased 12-fold. The total amount of detrusor collagen increased by a factor of 4, while the concentration of collagen decreased to 1/3 of the initial concentration. A longer period of obstruction, 4 months, did not further affect detrusor weight or collagen content or concentration. Ultrastructurally, both normal and hypertrophic detrusor showed a great number of collagen fibrils (probably synthetized by fibrocytes) between the smooth muscle bundles. Collagen fibrils (probably synthesized by the smooth muscle cells) could also, although less frequently, be found within the bundles. The decreased collagen concentration in the hypertrophic detrusor could largely be explained by a coalescence of the smooth muscle bundles resulting in a relative increase of this tissue component.