Fig. 8. Cholesterol depletion and incubation with water-soluble cholesterol has opposite effects on EGF binding. Untreated HEp-2 cells (control) and HEp-2 cells preincubated with either 10 mM MßCD for 15 minutes (MßCD), 1 µg/ml U18666A for 48 hours (U18666A), or 0.4 mg/ml water-soluble cholesterol for 30 minutes (cholesterol) were incubated with ¹²⁵I-EGF for 15 minutes on ice. Bound ¹²⁵I-EGF was measured as described in Materials and Methods. EGF bound to control cells was set to be 1 (approx. 1x10⁵ binding sites/cell). The figure shows one representative experiment of three measured in triplicate (means±s.e.m.).