Lack of Enhancing Effect of Mucosal Regeneration following Ulcération of the Urinary Bladder on N-Butyl-N-(4-Hydroxybutyl)nitrosamine Carcinogenesis in Rats1

The potential enhancing effects of the regeneration response of the urothelium following ulcération of the bladder mucosa on A/-butyl-/V-(4-hydroxybutyl)nitrosamine Carcinogenesis were examined in male Fischer rats. The carcinogen was adminis tered in the drinking water at a concentration of 0.05% for 2 weeks. Ulcérationwas performed by a freezing technique 24 hr before the administration or 24 hr or 8 weeks after the discontinuation of A/-butyl-/V-(4-hydroxybutyl)nitrosamine. No enhancing effects by ulcération were observed. Ulcération prior to carcinogen treatment decreased rather than increased the induction of bladder tumors to approximately one-half the incidence of the control. Ulcérationafter A/-butyl-A/-(4-hydroxybutyOnitrosamine did not change the frequency of tumor in duction. While the inhibitory effect of the prior ulcération may result from the exposure of fewer mature mucosal cells that are capable of activating the carcinogen, the ineffectiveness of the subsequent ulcérations suggests that a single wave of regeneration does not enhance the tumorigenic response of bladder mucosa.