The timing and extent of intraosseous hypoxia in the oxidative stress-induced rat osteonecrosis model

Using a rat oxidative stress-induced femoral head osteonecrosis model, we determined the presence/ absence and timing of the generation of hypoxia in the femoral head. DL-Buthionine-(S,R)-sulfoximine (BSO) 500 mg/kg was administered intraperitoneally to male Wistar rats. The rats were killed at 1, 3, 6, 12 hours, and 1, 3, 5 days after BSO administration, and the bilateral femora were removed. A group not administered BSO (control group) was also studied (each group n = 5). In the femoral heads of each group, the expression of hypoxia-inducible factor-1 alpha (HIF-1α) as an index of hypoxia was confirmed by the Western blot method, and quantified using analytical software. In the femoral head increased HIF-1α expression was found in all groups from 1 hour after BSO administration (p < 0.05). In particular, in all specimens of the group 3 hours after BSO administration the most intense expression of HIF-1α amounting to about 13-fold of that of control group was noted (p < 0.001). The present results suggested that in the extremely short period of 3 hours after BSO administration hypoxia severe enough to cause osteonecrosis was induced by oxidative stress in the rat femoral head.