Abstract: Objective To study the mechanism of 12-4-Y[1-ethyl -8- methoxy -5 phenyl pyrazole （5，1-a） isoquinoline]，a novel isoquinoline compound， on apoptosis of activated rat hepatic stellate cells （HSCs） in vitro. Methods HSCs-T6 cells were treated with 12-4-Y at different concentrations（5，10，20，40 and 80 μg/ml） for 12 h，24 h，36 h and 48 h，respectively. Cell proliferation was determined by MTT assay. Qualitative and quantitative cell apoptosis were measured by Hoechst staining and flow cytometry（FCM），respectively. The expression of caspase 3 and its active form were detected by Western blotting. Results The proliferation rates of HSC-T6 cells when incubated with 12-4-Y for 12 hours were dose-dependent decreased[（1.086±0.013），（1.055±0.019），（0.957±0.012），（0.793±0.021） and（0.553±0.031），significantly lower than that in control group （1.215±0.014），P<0.05 for all]； the time-dependent inhibition of cell proliferation was observed when the incubation concentration of 12-4-Y at dose of 20 μg/ml was fixed[（0.957±0.012），（0.852±0.024），（0.641±0.032） and （0.492±0.017） at 12 h，24 h，36 h and 48h，significantly lower than that in the control group（1.318±0.007），P<0.01 for all]；In cells treated with 20 μg/ml for 24h，the apoptotic rate revealed by flow cytometry analysis was （29.23±1.20）%，which was significantly higher than that in the control group[（5.47±1.39）%，P<0.001] and Hoechst staining showed obvious apoptotic bodies in HSCs-T6 cells，in addition，Western blotting analysis revealed increased expression of cleaved caspase3 compared with in the control group. Conclusion 12-4-Y has great potential in inducing HSCs apoptosis and the activation of caspase3 might be involved in this process.

Key words: Hepatic stellate cells, Isoquinoline compound, Apoptosis, Apoptosis body