BACKGROUND: It is a hot investigation to many scholars that how to cure and prevent renal ischemic reperfusion injury in a utility way, but the mechanism is unclear at present. The investigation indicates that aquaporiin-1 plays an important role during this process. OBJECTIVE: To research the correlation between aquaporin-1 expression and renal function change following renal ischemic reperfusion injury. DESIGN, TIME AND SETTING: A randomized controlled animal experiment was performed at Histology and Embryology Laboratory of Dalian Medical University from June 2007 to December 2008. MATERIALS: A total of 80 healthy female adult Wister rats were randomly divided into control group and ischemia-reperfusion group. Rats in each group were observed at days 1, 2, 3, 5, and 7 after operation, with 8 rats for each group. The ischemia-reperfusion injury was established on the left kidney. METHODS: Right kidney was removed. The left renal pedicle was freed and occlused to establish ischemia-reperfusion injury model. After 40 minutes, the blood was re-flowed. If the kidney colored from dark red to bright red within 2-5 minutes, the ischemia-reperfusion injury models were successfully established, and the thrombus was not formed in the kidney vessels. If the kidney was still dark red after 5 minutes, the thrombus was formed, and the rats were excluded from the ischemia-reperfusion group. The abdomen was sutured after 40 minutes.MAIN OUTCOME MEASURES: Rats were sacrificed at days 1, 2, 3, 5, and 7 after ischemia-reperfusion injury. Samples of urine, serum, and kidney were performed with the examinations of urine, renal function, renal pathology and morphology, immunohistological assay of aquaporiin-1, and RT-PCR assay. RESULTS: After ischemia-reperfusion injury, the rats had hydrouria, urine osmotic pressure depress, symptoms of carnine and urea nitrogen increasing. HE staining demonstrated that renal tubular epithelial cells were swelling, necrosis, and desquamate. Aquaporin-1 expression and its mRNA level was decreased; in particular, the expression and level were the lowest at day 1 after ischemia-reperfusion injury and recovered to normal value at day 5 after ischemia-reperfusion injury. CONCLUNSION: The down expression of aquaporin-1 maybe one of the important indicators to reflect renal functional changes of acute renal failure following renal ischemia-reperfusion injury.