Abstract: AIM: To investigate the damage of alpha and beta cells on islets of diabetic rats in different dosages and injecting times of streptozotocin (STZ).METHODS: Wistar rats were divided into six groups: control group, group A (single injection with 50mg·kg^-1STZ), group B (injection with 50 mg·kg^-1·d^-1STZ for two days), group C (injection with 50mg·kg^-1·d^-1STZ for three days), group D (injection with 30 mg·kg^-1·d^-1 STZ for five days) and group E (single injection with 80 mg·kg^-1STZ). The body weights and concentrations of peripheral glucose of rats were measured regularly. Then the pancreases of rats were selected to make tissue slices. The tissue slices embedded in paraffin were histological observes under the light microscope after staining with Hematoxlin and Eosin (HE), Azan and immunohistochemical techniques.RESULTS: Insulitis was observed in each group throughout the term of experiment. It was more serious in all rats that were injected with STZ than those in the control group. The inflammation, vacuolization and fibrosis of islets in the group D were more serious than those in the other groups. The amount of islets, the average area of islets, the area of beta cells, the ratio of the area of beta cells and the average area of islets in each group were significantly decreased, especially in the group C, D and E. Conversely, the area of alpha cells, the ratio of the area of alpha cells and the average area of islets in each group significantly increased as alpha cells appeared.CONCLUSION: STZ can induce chemical insulitis and autoimmune insulitis, destroy both alpha and deltas cells, and make vacuolization and fibrosis in islets. Single, high dose of STZ can cause the greatest damage.

Key words: diabetic rats, streptozotocin, immunohistochemical techniques, anti-insulin antibody, anti-glucagon antibody