Fig. 3. Effect of COase and/or SMase treatment on [³H]CE and ¹²⁵I-protein association of LDL and HDL₃ in HepG2 cells. HepG2 cells were treated with 1 U/ml COase or 0.5 U/ml SMase or both enzymes for 1 hour at 37°C. The cells were then processed for [³H]CE association (black bars), CE selective uptake (CE association – protein association and degradation) (white bars), ¹²⁵I-protein association (hatched bars) and degradation (cross-hatched bars), with 20 µg/ml radiolabelled LDL (A) or HDL for 3 hours at 37°C (B). Results are shown as mean percentage±s.e.m. Control values in µg protein/mg cell protein were set as 100% and were: 0.507±0.066, 0.444±0.066, 0.123±0.015, 0.029±0.001 for [³H]CE-LDL association (n=7), LDL-CE selective uptake, ¹²⁵I-LDL protein association (n=7) and degradation (n=2) respectively; and 0.332±0.058, 0.271±0.058, 0.067±0.008 for [³H]CE-HDL₃ association (n=7), HDL₃-CE selective uptake and ¹²⁵I-HDL₃ protein association (n=7) respectively (mean±s.e.m.). Statistically different values from the control values (without enzymes) are indicated as: ^aP<0.05; ^bP<0.01 and ^cP<0.001.