A Comparison of Cell Cycle-related Changes in Postmitotic and Quiescent AF8 Cells as Measured by Cytofluorometry after Acridine Orange Staining1

AF8 cells were collected by mitotic detachment or made quiescent by serum restriction. Replated mitotic cells or serum-stimulated quiescent cells were then compared by flow cytofluorometry, with the use of acridine orange staining. Red fluorescence intensity (F ,„„,) was the same in quiescent cells and in cells immediately after mitosis. However, F „¿ „„ increased very rapidly in postmitotic cells, while there was a delay in serum-stimulated quiescent cells. F ,,,„ reached a peak at 4 hr in postmitotic cells and between 16 and 19 hr in serum-stimulated quiescent cells. A similar delay in the time of entry into S phase occurred after serum stimulation of resting cell populations. The results are compatible with the hypothesis that cells after mitosis may enter a state that is different from the state of cells made quiescent by serum restriction.