title: Effects of carcinogen dose on the characteristics of the tracheal tumor response induced by N-nitroso-N-methylurea in hamsters.
abstract: Tracheal tumors were induced by repeated intratracheal exposures to the carcinogen N-nitroso-N-methylurea (NMU), using a catheter system previously described. Carcinogen concentrations of 0.25, 0.50 and 1.0% were employed in 20 or 30 twice-weekly exposures. Most of the tumors developed in the mid-portion of the tracheas. Virtually all tumors developed after the end of the 10- to 15-week exposure period. Tumor incidence ranged from 20-94% with mean tumor induction times of 13-46 weeks, depending on NMU concentration and frequency of exposure (i.e., dose). At lower doses, mostly non-invasive tumors were induced; at higher doses, mostly invasive carcinomas of various histological types (epidermoid, adeno-, epidermoid-adeno, and anaplastic large- and small-cell carcinomas) were induced. Adenocarcinomas were most frequent at low NMU concentrations. The possible mechanisms of the carcinogen dose effects are discussed.
mesh_terms: D000230:Adenocarcinoma / Q000139:chemically induced*; D000818:Animals; D001284:Atrophy / Q000139:chemically induced; D002278:Carcinoma in Situ / Q000139:chemically induced; D002294:Carcinoma, Squamous Cell / Q000139:chemically induced; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D006965:Hyperplasia / Q000139:chemically induced; D008297:Male; D008647:Mesocricetus; D008679:Metaplasia / Q000139:chemically induced; D008770:Methylnitrosourea / Q000008:administration & dosage*; D009374:Neoplasms, Experimental / Q000139:chemically induced; D009607:Nitrosourea Compounds / Q000008:administration & dosage*; D011230:Precancerous Conditions / Q000139:chemically induced; D013997:Time Factors; D014132:Trachea / Q000473:pathology; D014134:Tracheal Neoplasms / Q000139:chemically induced*
chemical_list: D009607:Nitrosourea Compounds; D008770:Methylnitrosourea