3H-thymidine uptake by the rat urinary bladder after partial outflow obstruction.

Partial outflow obstruction induces marked changes in detrusor contractile function and morphology. One common finding in all experimental animal models of outflow obstruction is a significant increase in bladder mass. It is not clear which tissue compartments undergo hypertrophy, hyperplasia, or both. The present study was designed to evaluate the time-related changes in 3H-thymidine uptake and distribution within each tissue compartment induced by partial outflow obstruction using autoradiography. Partial outlet obstruction in rats induced a mild 2-fold increase in mass over a 14 day period. DNA synthesis increased significantly at 1 day following surgery, and remained increased through 7 days. DNA synthesis returned to control levels by 14 days. Distribution studies (using autoradiography) demonstrated a marked increase in the number of labelled urothelium cells at 1 and 3 days after obstruction. Sham surgery also initiated an increase in the number of labelled cells in the urothelium at 1 day. Although both sham and obstructive surgeries induced substantial increases in the labelling of cells within the connective tissue components, the magnitude of the increase in labelled connective tissue cells of the obstructed bladders was greater than that of the sham group. The number of labelled smooth muscle cells of the obstructed bladder increased significantly at 3, 5, and 7 days. However, there were no changes in smooth muscle incorporation of 3H-thymidine by the sham groups. In conclusion, partial outflow obstruction induced time-dependent increases in bladder wall proliferation. The urothelium and connective tissue were the compartments first affected, followed by smooth muscle.