AIM: To investigate the effects of AngⅡon the production of ET-1, NO from myocardial fibroblasts (MFs) of adult rat. METHODS: MFs were extracted by enzymatic digestion and anchorage velocity-dependent separation method. In this study, the changes of ET-1 and NO production from MFs in the second passage were examined by radioimmunoassay and by nitrate reductase-dependent assay, separatively. RESULTS: In a specific concentration range, AngⅡ increased ET-1 synthesis in MFs in a concentration-dependent manner. Losartan, the antagonist of angiotensin Ⅱ 1 type recepters (AT 1R), blocked the above effects. AngⅡ may inhibit NO synthesis in MFs. When MFs were treated with losartan+AngⅡ, the production of NO increased significantly, and was higher than that treated with the others( P