Aim:To determine whether all-trans retinoic acid (atRA) acts to modulate angiotensin Ⅱ (Ang Ⅱ) -induced cardiac fibroblast cell growth and collagen secretion.Methods:Cultured neonatal rat cardiac fibroblasts (CF) were used in the experiment.A 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyl tetrazolium bromide (MTT) assay was used to detect cell growth of the CF;and immunocytochemistry and Weste blotting were used to measure the production and secretion of collagen and the expression of transforming growth factor-β1 (TGF-β1) by the CF.Results:atRA (1×10-7 to 1×10-5mol/L) inhibitedtheAngⅡ-induced increase in cell growth of CF (P＜0.05).Ang Ⅱ stimulated the secretion of collagen types Ⅰ and Ⅲ by the CF. This eflfect was blocked by AT1 receptor antagonist losartan (1×10-6 mol/L) ,but notbyAT2 receptorantagonistPDl23319 (upto 1×10-6mol/L).Exposure of CF to atRA (1×10-5mol/L) attenuated the Ang Ⅱ-induced increase in the secretion of collagen types I and Ⅲ (P＜0.05).atRA (1×10-5mol/L) also blocked the Ang Ⅱ-induced increase in the expression of TGF-β1.Conclusion:atRA inhibits the Ang Ⅱ-induced increase in cell growth and collagen secretion of neonatal rat CF.The effect of atRA is possibly mediated by lowering the TGF-β1 level.These observations support the notion that atRA is a potential candidate for the prevention and therapy of cardiac remodeling.