INDUCTION OF ADENOCARCINOMAS IN THE SUBMANDIBULAR SALIVARY-GLANDS OF FEMALE WISTAR RATS TREATED WITH 7,12-DIMETHYLBENZ(A)ANTHRACENE

In 12 male and 12 female Wistar rats, 7-9 weeks of age, a solution of 0.05 ml of 1% 7,12-dimethylbenz(a)anthracene (DMBA) dissolved in aceto ne was injected directly into the submandibular glands biweekly, after the gland had been injured. In some rats the carcinogen was injected 1 week after the injury. Each rat received six to seven injections. Sw elling was observed in the submandibular gland region as early as 4 we eks after the last injection. The animals were killed 4-8 weeks after the last injection and glands with tumour tissues were processed for l ight microscopy. The control rats of the same age that received a corr esponding amount of acetone only (three male, three female), carcinoge n injection alone (three male, five female), and injury only (four mal e, four female) were killed at the same time, Histological examination revealed adenocarcinomas of the submandibular gland in 12/12 (100%) f emale rats, six of which were associated with fibrosarcomas. The adeno carcinomas basically consisted of ductal and glandular structures. Som etimes tubular, cystic, papillary-cystic and cribriform-like structure s were also observed. Male rats mainly developed fibrosarcomas, althou gh there was one squamous-cell carcinoma. The reasons for the sex diff erence are not known. One adenocarcinoma developed in the submandibula r gland of a female rat (1/5) that received carcinogen injections alon e. Thus direct injections of DMBA into the submandibular gland produce adenocarcinomas in female Wistar rats.