Abstract: Objective To explore histological characters of the digestive tract of Sub-plateau acclimatized SD rats and 20 KM mice and to provide comparative data for pathological inspection, toxicological studies and drug safety evaluation. Methods Twenty SD rats and 20 KM mice were divided into flatland group and sub-plateau group, each group include 10 ones. Animal quality and breeding condition complied with the state standard without any infectious disease after quarantine. Tissues of digestive tract were collected after euthanasia and autopsy . Tissues were fixed with 10% neutral formalin, the pathologic slide specimens were prepared by HE staining after paraffin imbedding, and then which were observed and studied under the light microscope. The same and different histological structure characters of them were summarized by comparative study. The histological structures of digestive tract were observed by light microscopy. Results (1) Inflammation was a common spontaneous lesion of digestive tract in all groups, but imflammation in the sub-plateau groups were more serious than the flatland groups. (2) Widening of space between lingualis, and more nuclear chains of lingualis were seen in sub-plateau groups. (3) Goblet cell metaplasia existed in intestinal mucous membrane of sub-plateau groups. (4) The mast cells were observed much easier in muscle stomach of sub-plateau groups. Conclusion The digestive tract characters of SD rat and KM mice are basically the same, but there are some histological differences in digestive tract between the flatland and sub-plateau group, which is an adaptive response of cell and tissue, and this difference should be fully considered in experimental research, toxicological studies and drug safety evaluation.

Key words: Rat, Mouse, Digest tract, Flatland, Sub-plateau, Comparative histology