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! I I I I I I I I I I I I I I I I I AU'rHOR: KARBE, EBERHARD AND KARl KOSTER DAT~: 1974 ~: CARCINOGENICITY OF INHALED CIGARETTE SMOKE IN THE NMU-PRETREATED HAMSTER LARYNX CITATION= EXPERIMENTAL LUNG CANCER - CARCINOGENESIS AND BIOASSAYS, INTERNATIONAL SYMOSIUM HELD AT BATTELLE SEATTLE RESEARCH CENTER, JUNE 23-26 1974, SPRINGER-VERLAG, pp. 369-382 122 l-month old Syrian golden hamsters were pretreated intratracheally with NMU (N-methyl-N-nitroso- urea) using various dosages and melhods. After pretreatment of 1 month, half of animals in each of 7 groups were expo~d 5day,week for 6 months to diluted ('7+1) cigarelte smoke (flue-cured tobacco blend cigarettes). Other half of animals placed in inhalation tubes, but not expend to smoke. 36 additional animals, not pretreated with NMU were used as controls, half of which were exposed to smoke for .6 months. A grading system of epithelial changes in the larynx was established that included hyperplastic and metaplastic lesions (grades 1 to 3), severe endophytic proliferations and carcinoma in situ (grade 4), and epidermoid carcinomas (grade 5). FINDINgS/RESULTS: 6 of 43 NMU-pretreated and smoke-exposed hamsters had epidermoid carcinomas (grade 5), whereas 2 out of 41 NMU-treated but not expo~d to smoke had lesions of this type. The corresponding numbers of animals with grade 4 lesions were 11 and 2, respectively. Thus, inhalation of smoke increased the incidence of grade-4 and grade-5 lesions in NMU-initiated hamster about 4 fold. No such lesions were ob~rvcd in the 36 control animals. CONCLUSIONS: The intratracl~a[ instillation of NMU in hamsters appears to be a suitable method of examining the tumor-enhancing effect of inhaled cigarette smoke for experimental purposes. Such a NMU treatment may lead to a new bioassay for weak particulate carcinogens or cocarcinogens. I