Abstract: Objective To study the role of apelin in the prevention of renal interstitial fibrosis induced by hypoxia in rats. Methods The animal model of hypoxic renal interstitial fibrosis was established by exposing the rats to isobaric hypoxic chamber for 4 weeks (8h/d，6d/week). Thirty male Sprague-Dawley rats were randomly divided into control group, hypoxic group and hypoxia with apelin (lOnmol/kg/d) group (HA). [pGlu]apelin-13 was administered into the rats of apelin groups by mini-osmotic pump subcutaneously. Serum creatinine (Scr) and urea nitrogen (BUN) were measured. The renal homogenates were assayed for the activity of superoxide dismutase (SOD) and the contents of malondialdehyde (MDA) and hydroxyproline. Meanwhile, the renal specimens were examined by VG staining to examine renal interstitial fibrosis. Results (1) There was no significant difference of Scr and BUN among three groups. (2) The content of hydroxyproline in hypoxic group was 35.4%(P＜0.01) higher than that of control group, while apelin group was 24.6%(P＜0.05) lower than hypoxic group. (3) The activity of SOD in hypoxic group was lower than that in control group by 55.1% while the content of MDA was higher by 38.9% (all P＜0.01). Apelin treatment increased the activity of SOD by 20.7% (P＜0.01) while decreased the content of MDA by 55.7 (all P＜0.01). (4) VG staining revealed that renal vascular fibrosis was found in hypoxia groups，which was significantly alleviated by apelin treatment. Conclusions Apelin could play an important role in treatment of hypoxic renal interstitial fibrosis of rats, and the mechanisms of protection were associated with inhibition of oxidative stress.

Key words: Apelin, Renal interstitium, hypoxia, Superoxide, Malondialdehyde