AIM To investigate the mechanisms ofsalvianolic acid A(SA-A)against liver fibrosisin vitro.METHODS NIH/3T3 fibroblasts were culturedroutinely,and incubated with 10-4mol/L-10-7mol/L SA-A for 22 h.The cell viability wasassayed by[~3H]proline incorporation,cellproliferation by[~3H]TdR incorporation,cellcollagen synthetic rate was measured with[~3H]proline impulse and collagenase digestionmethod.The total RNA was prepared from thecontrol cells and the drug treated cellsrespectively,and α(1)I pro-collagen mRNAexpression was semi-quantitatively analyzedwith RT-PCR.RESULTS 10-4mol/L SA-A decreased cellviability and exerted some cytotoxiciy,while10-5mol/L-10-7mol/L SA-A did not affect cellviability,but inhibited cell proliferationsignificantly,and 10-6mol/L SA-A had the besteffect on cell viability among theseconcentrations of drugs.10-5mol/L-10-6mol/LSA-A inhibited intracellular collagen syntheticrate,but no significant influence on extracellularcollagen secretion.Both 10-5mol/L and10-6mol/L SA-A could decrease α(1)I pro-collagen mRNA expression remarkably.CONCLUSION SA-A had potent action againstliver fibrosis.It inhibited NIH/3T3 fibroblastproliferation,intracellular collagen syntheticrate and type I pro-collagen gene expression,which may be one of the main mechanisms of thedrug.