Abstract: Objective To observe the differences on histology of the cardiovascular system in 6 commonly used laboratory animals. Methods Six species of laboratory animals, including 30 rhesus monkeys, 20 KM mice, 20 SD rats, 18 Japanese white rabbits,16 Beagle dogs, 20 tree shrews were selected. Except the mice were killed by cervical dislocation, other animals were sacrificed by intravenous anesthesia, and the heart and some blood vessels were removed, and then were fixed by 10% formalin and sealed in glass containers after pathological anatomy. The heart and blood vessels were processed by gross examination, routine pathological HE staining, necessary special staining and immunohistochemical staining, then the similarities and differences of cardiac and vascular structure and cell structure were observed under the microscope. Results (1) Six species of animals have no significant differences in the structure of the heart, the difference only exist in myocardial cell morphology. (2)Cardiac interstitial collagen deposition situation is different in the six species of animals. (3) The distribution of nutrient vessels among myocardial fibers are different in 6 species of animals. (4) Six species of animals have no significant difference in arterial vascular structure, only the thickness of tunica media and the content of collagen and elastic fibers are different. Conclusion The comparison on histopathology of cardiovascular system in six species of animals provides a reference for teaching and research works,and also provides appropriate basis and control for the development of“experimental animal pathology testing standards”.

Key words: Laboratory animals, Rhesus monkey, Beagle dog, Tree shrew, Japanese white rabbit, SD rat, KM mouse, Cardiovascular system, Comparative histology