Fluorescein isothiocyanester(FITC)lablled high density lipoprotein-2 keeps the biological activities of native HDL.After human SMMC-7721 hepatocarcinoma cells were incubated with FITCapolipoprotein E-free HDL-2 at 37℃ for 3h, the cellassociated and endocytic fluorescent strength (FS)were 13.5±0.8 and 9.2±0.5(x±s,n=2) respectively. The cell-released trichloroacetic acid (TCA)precipitable FS and TCA-soluble FS were 5.1±0.4and 0.67±0.17 after the cells were incubated further at 37℃ for 2 h. And the cell-released TCA-precipitable FS was 0.41±0.16 at 4℃ for 2h.These results suggest that:①cell-internalized doesn't take lysosomal pathway;②the released of cell-internalized HDL-2-apolipoprotein is a temperature-dependent retroendocytosis.