The kinetics of cellular proliferation in rat urinary bladder treated with N-butyl-N-(4-hydroxybutyl)nitrosamine.

The cellular proliferation of the bladder epithelium was determined sequentially in rats treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). The incorporation of bromodeoxyuridine (BrdUrd) into the DNA synthesis phase was determined by an in vitro labeling technique. The percentage of labeled cells was expressed as the labeling index (LI). The average LI values in normal subjects and cancer-bearing subjects were 5.1(%) and 24.2(%) respectively. With the transition of the bladder epithelium from simple hyperplasia to cancer, the LI values of the bladder epithelium were increased. Cases of papillary or nodular (PN) hyperplasia were divided into two types according to the localization of the BrdUrd-labeled cells. The LI in PN hyperplasia was 12.4(%); the difference from cancer was significant. In another experiment, the effect of partial cystectomy on bladder tumors was examined. The group with partial cystectomy showed increases in grade and stage of cancer, and the LI of cancer was more than that in the group without partial cystectomy. The results indicate that partial cystectomy may play a role as promotor for bladder tumors. The current study may be of more practical value than is the conventional one for investigating the histogenesis and progression of human bladder cancer.