OBJECTIVE: To observe the effect of high glucose, angiotensin II (AngII) and Losartan on the expression of connective tissue growth factor (CTGF) mRNA in cultured mesangial cells (MCs). METHODS: MCs of SD rats were isolated and cultured. High glucose (30 mmol/L) and AngII (10(-9), 10(-7), and 10(-5) mol/L) were added to the medium for 72 hours to observe the influence on CTGF mRNA expression. Losartan of 10(-5) mol/L and AngII of 10(-5) mol/L were added to the medium to observe the effects of Losartan on CTGF mRNA expression stimulated by AngII. The expressions of CTGF mRNA were detected by reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: RT-PCR showed that high glucose and AngII up-regulated the expression of CTGF mRNA, and AngII stimulated the expression in a dose-dependent manner. Expression of CTGF mRNA induced by AngIIwas partially suppressed by 10(-5) mol/L Losartan (P < 0.05). CONCLUSIONS: High glucose and AngII can enhance the expression of CTGF mRNA and thus be involved in the process of renal fibrosis. Losartan can have a partial fibrogenesis-inhibiting effect, with implications for the treatment of renal fibrosis.