Effect of erythropoietin on expression of aquaporin-2 in kidney of young rats with partial unilateral ureter obstruction

Abstract

Objective To investigate the effect of erythropoietin (EPO) on expression of aquaporin-2 (AQP2) in the kidney of young SD rats with partial unilateral ureter obstruction (PUUO). Methods Twenty-four young SD rats were randomly divided into 3 groups (PUUO group, n=8; PUUO+ EPO group, n=8; sham group, n=8). The PUUO model was built by embedding the upper quarter of the left ureter into psoas muscle.EPO(500 U/kg) was given to PUUO+ EPO rats at 1 h after surgery, and then repeated 1, 3, 5 days later after surgery by intraperitoneal injection and the same volume of 9 g/L saline was simultaneously given to PUUO rats.The sham group was prepared in parallel by way of laparotomy and free dissection of the left ureter.In 1 week after surgery, the left kidneys of rats were harvested to examine the effect of EPO on the expression of AQP2 in inner medulla by immunohistochemistry, real-time PCR and Western blot. Results Immunohistochemistry showed that the expression of AQP2 in the collecting duct in PUUO group was significantly downregulated than those in sham group and PUUO+ EPO group, whereas, it was slightly weaker in PUUO+ EPO group than those in sham group.These results were further confirmed by Western blot, and the relative quantity of AQP2 in PUUO group was also lower than those in PUUO+ EPO group and sham group (0.290±0.016 vs 0.640±0.106 vs 0.840±0.134, P<0.05). Real-time PCR showed that the level of AQP2 mRNA in PUUO group was lower than those in PUUO+ EPO group and sham group (ΔCt values of 3 groups were -7.60±0.18 vs -9.70±0.54 vs -10.80±0.31, P<0.05). Conclusions EPO can partially prevent the downregulation of AQP2 in young PUUO rats, and its mechanism needs to be further investigated. Key words: Erythropoietin; Partial unilateral ureter obstruction; Aquaporin-2; Kidney