Intratracheal instillation studies with 7H-dibenzo(c,g)carbazole in the Syrian hamster

The morphologic effects and the retention and distribution times of single and multiple intratracheal instillations in Syrian hamsters of 7H-dibenzo[c,g]carbazole (DBC) and benzo[a]pyrene (BP) were compared. A single instillation of DBC induced slight changes in the hamster respiratory tract; however, five treatments caused tracheobronchial epithelial proliferation, cell hyperplasia, and occasionally, squamous metaplasia. The particle size of both carcinogens was approximately the same. BP in saline remained longer in the lungs than did DBC in saline. The shortest retention time was recorded when DBC was administered in aqueous solution, whereas multiple doses of DBC in aqueous solution did not markedly affect retention time. DBC passed from the lungs to the intestinal tract and was mainly excreted in the feces.