The effect of environmental stress stimuli on cell division in rat palatal epithelium

The effect on cell proliferation of procedures commonly used in studies in laboratory animals was examined in the palatal epithelium of rats. Groups of rats were exposed to ether anaesthesia, immobilization in the supine position or to cage change. Animals left undisturbed in the cages during the experiment were used as controls. At intervals of 30 min, four animals of each group were killed and histological sections of the palatal mucosa were prepared. The number of prophases, metaphases and ana/telophases in the epithelium was counted and related to 1 mm2 of the surface. Thirty minutes after the various procedures the number of metaphases and ana/telophases were extremely low. After a further 30 min a high number of prophases was observed. The number of metaphases rose within the following 30 min, during which time the number of ana/telophases also reached a maximum. These observations indicate that the environmental stimuli have blocked the entrance of cells into mitosis and have resulted in an accumulation of cells, which, following the raising of the blockade, pass through the various stages of the mitotic phase. In studies of cell population kinetics the blockade of cell division as a result of environmental stress stimuli may lead to misleading results.