Lack of enhancing effect of mucosal regeneration following ulceration of the urinary bladder on N-butyl-N-(4-hydroxybutyl)nitrosamine carcinogenesis in rats.

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