Effect of Outlet Obstruction on 3H-thymidine Uptake: a Biochemical and Radioautographic Study

Experimental outlet obstruction in the rabbit is characterized by a rapid and substantial increase in urinary bladder mass. Although it is clear that both the smooth muscle and connective tissue compartments are increasing in mass, there is little information on the mechanisms by which this increase in mass occurs. As an initial investigation in this process, urinary bladders from normal and obstructed NZW rabbits were exposed in vitro to tritiated thymidine (3H-TdR) in order to determine which populations of cells are induced to synthesize DNA following outlet obstruction, and when, after obstruction, such synthesis occurs. Biochemical analysis of nucleic acids was performed on each specimen to determine total and radioactive DNA. These analyses showed a marked increase in DNA synthesis at 24 hours following obstruction which remained relatively high through seven days after obstruction. There was a decline in labelling at 14 days. Incorporation of radioactive label peaked at three days and declined to control levels by 14 days. Samples of tissue were taken from each subject and processed for radioautography. At 24 hours after obstruction, significant numbers of cells of the basal cell layer of the urothelium are observed to be actively involved in DNA synthesis, while the other two tissue compartments (muscularis and connective tissue) show no significant changes when compared to normal specimens. Connective tissue, on the other hand, showed significantly increased levels of labelling above control level from three to 14 days after obstruction. Smooth muscle cells were observed to be frequently labelled in only one of the experimental bladders observed three days after obstruction.