Epithelial lesions induced by N-nitrosoheptamethyleneimine in host and transplanted rat tracheas.

N-Nitrosoheptamethyleneimine (NHMI) was given by gastric intubation, at a dosage of 10 mg/kg body weight twice weekly for 5-20 weeks, to F344 rats bearing subcutaneous tracheal transplants. Groups of 5 rats were killed at 5, 10, 15, and 20 weeks, and 1 group was killed at week 33 of the experiment (13 weeks after the last NHMI dose). Sequential changes in host tracheas consisted of hyperplasia with complete loss of mucociliary epithelium, squamous metaplasia, intense mononuclear infiltration, reestablishment of mucocillary epithelium (during the course of NHMI administration) except for focal areas of hyperkeratotic squamous metaplasia or marked dystrophic changes, and finally, papillomas, polyps, and invasive squamous cell carcinomas. Lesions in tracheal transplants consisted mostly of atrophic and dystrophic changes, with only a few small foci of squamous metaplasia and no neoplastic changes.