Reappearance of the c-kit receptor on the cell surface requires new protein synthesis. Display of the c-kitreceptor on MO7e cells proliferating in GM-CSF, before exposure to SCF, is shown in the left portion of the figure. MO7e cells were incubated with SCF (100 ng/mL) for 1 hour at 37°C to induce internalization of the c-kit receptor. The cells were washed to remove SCF, and reappearance of the c-kit receptor on the cell surface was assessed by flow cytometry at various time points (0 to 4 hours) after removal of SCF. MO7e cells were incubated in parallel in the presence of cycloheximide (10 μg/mL) to inhibit new protein synthesis. The data are presented as the mean (± SEM) of triplicate values. The cells incubated in the absence of cycloheximide displayed more cell surface c-kit receptor than the cells incubated in the presence of cycloheximide (*P < .01, Student's t-test).