Fig. 3.

¹²⁵I-PFO* binding to SV-589 cells after prior treatment with different sterols. On day 0, cells were set up in medium A at 1 × 10⁵ cells per 60-mm dish. On day 2, cells were switched to lipoprotein-deficient medium C. On day 3, cells were refed with medium C containing 10 μM compactin and 50 μM sodium mevalonate and then incubated for 16 h at 37 °C. On day 4, each dish received fresh medium C containing 10 μM compactin, 50 μM sodium mevalonate, and varying concentrations of the indicated sterol complexed with MCD (sterol/MCD molar ratio of 1:12). After incubation for 3 h at 37 °C, the cells were washed five times as described in Materials and Methods and then incubated with 2 mL ice-cold buffer E containing 5 μg/mL ¹²⁵I-PFO* (30 × 10³ cpm/μg) for 30 min at 4 °C. The total amount of cell surface ¹²⁵I-PFO* binding was determined as described in Materials and Methods. Each value represents the average of duplicate incubations.