Hamster Cheek Pouch Response to Varying Lengths of Carcinogen Exposure

Abstract

Young adult albino hamsters of both sexes were divided into 13 groups of 13 animals. An 0.5% mineral oil solution of 7, 12- dimethylbenz ([alpha]) anthracene was applied triweekly with a number 4 camels hair brush to both pouches of the animals in 12 groups. At the end of each week 1 group was omitted from the painting procedure. The latent period for initial tumor formation was recorded for each animal. After 21 weeks, all animals were sacrificed and the number and size of tumors in each pouch recorded. Formalin fixed pouches were sectioned and stained with hematoxylin and eosin. Four animals painted 1 week, 7 animals painted 2 weeks, and all animals painted 3 or more weeks developed tumors by 21 weeks. Mean latent period for tumor development in animals painted 3 weeks was significantly longer than that of animals painted for a longer period. In general, the longer the animals were painted, the greater the number and the size of the tumors that developed by 21 weeks. Histologic sections of pouches from all animals in groups 1 and 2 revealed moderate epithelial hyperplasia and some disruption of arrangement and uniformity of the basal cell layer. There were no conspicuous differences in the histology of tumors regardless of the group in which they appeared.