Cyclic changes in fluorescence polarization of a membrane probe during the cell cycle of an erythroid precursor cell line

The membrane lipid bilayer of the K562 cell line undergoes marked changes during cell cycling. These changes can be detected by measuring the fluorescence polarization of the rod-like hydrophobic probe 1,6-diphenyl-1,3,5-hexatriene. Single-cell measurements were performed by flow microfluorometry on synchronized K562 cells. The fluorescence polarization of the probe increased after cell division and was maximal during the S phase. Concomitant with the transition from S to G2 and M phase was a decrease in fluorescence polarization. The data are interpreted as reflecting a minimal membrane lipid fluidity during the S phase and a maximal fluidity during the G2/M-phase of the above erythroid precursor cell line.