Abstract: Aim To evalute the effects of losartan on the cardiac function and secretion of nitric oxide (NO) and endothelin (ET) in patients with congestive heart failure(CHF). Methods Sixty patients with class II ~ Ⅳ CHF were randomised to receive a 12 weeks of routine therapy either with losartan (n =30)to be added from 25 mg to 50 mg daily or with enalapril (n = 30) to be added from 2.5 mg to 5 mg daily. The cardiac systolic and diastolic funtion and the levels of NO and ET were observed before and after therapy respectively with 30 normal control subjects seving as control. Results The abnormal cardiac systolic and diastolic function parameter were present in patients with CHF. The ET and NO levels in CHF patients were significantly higher than those in the control group(P <0.05). NYHA function class was improved in 85% of losartan treated patients and in 84% of enalapril-treated patients after 12 weeks as compared with cardiac function at baseline. ET and NO levels were significantly reduced(P <0.01) NO/ ET ratio was increased (P <0.05) after 12 weeks of therapy in two active groups. Conclusion The systolic and diastolic functions of patients with CHF are greatly improved by losartan treatment, which reverses the imbalance of NO/ ET and it is suspected that this action may be another important mechanism of its treating heart failure

Key words: losartan, congestive heart failure, endothelin nitric oxide