Abstract: AIM The present investigation studied the effects of obestatin on changes in cardiac function and urine volume in post infarction chronic heart failure (CHF) rats. METHODS Thirty-six rats were randomly equally divided into 6 groups. Five CHF groups were established by ligating the left anterior descending artery (LAD), whereas rats in the sham group underwent chest operation without LAD ligation. After a 16-week normal diet, left ventricular ejection fraction (LVEF) was measured by echocardiography and a 24-hour urine was collected to measure urine volume in all sham and CHF rats. RESULTS The sham group was given intraperitoneal injection (IP) of saline, while the other five CHF groups were given IP of saline, AVP, ghrelin, obestatin 50 μg/(kg·d) and obestatin 100 μg/(kg·d), respectively. After the 4-week IP, LVEF was measured by echocardiography and a 24-hour urine was collected to measure urine volume in all sham and CHF rats. Compared with baseline, after the 4-week treatment, LVEF and urine volume increased significantly in the obestatin 100 μg/(kg·d) treatment group (P<0.05). LVEF decreased (P<0.01) and the urine volume also decreased significantly (P<0.05) in the AVP treatment group. LVEF increased significantly (P<0.01) but there were no significant changes in urine volume in the Ghrelin treatment group. There was no significant change in LVEF or urine volume in the sham group given saline or the CHF group given saline or the CHF group given obestatin (50 μg/kg·d). CONCLUSION In summary, high dose IP of obestatin, in a dose of 100 μg/(kg·d), improves cardiac function and urine volume in surgically prepared CHF rats.