Fig. 4. Time (A) and concentration (B) dependence of native and tyrosylated specific cholesterol ether uptake by J774-A1 cells. J774-A1 cells were cholesterol loaded with AcLDL (50 µg apo B/ml) as described in Materials and Methods. After an 18 hour equilibration period, cells were incubated for different times with 25 µg apo A-I/ml of native (•) or tyrosylated () [³H]cholesteryl hexadecyl ether-HDL₃ (A) or for 3 hours at 37°C with the indicated final concentrations of native (•) or tyrosylated () [³H]cholesteryl hexadecyl ether-HDL₃ (B), in the absence or presence of a 50-fold excess of the corresponding unlabeled HDL₃. After cell washing, the specific [³H]cholesteryl hexadecyl ether cell uptake was determined by radioactivity measurement. Each value represents the mean±s.e.m. of three independent experiments using different lipoprotein preparations. ^*P<0.05, ^**P<0.02.