Abstract
The metachromatic fluorochrome acridine orange was used to differentially stain DNA and RNA in Chinese hamster ovary (CHO) cells and in mitogenโstimulated human lymphocytes during their progression through the cell cycle. Green and red fluorescence of individual cells, representing cellular DNA and RNA, respectively, was measured by flow cytometry.
CHO cells were synchronized by selective detachment at mitosis. Their rate of progression through G~1~ and subsequently through S phase correlated with the content of stainable RNA. The mean duration of the G~1~ phase was 5.2 hours for cells with high RNA content (highest 25 percentile population) and 8.1 hours for cells with low RNA (lowest 25 percentile). The duration of S phase was 5.9 and 7.5 hours for highโ and lowโRNA, 25 percentile subpopulations, respectively.
Lymphocytes synchronized at the G~1~/S boundary by hydroxyurea or 5โfluorodeoxyuridine showed extremely high intecellular variation with respect to content of stainable RNA. After release from the block they traversed S phase at rates linearly proportional to the content of stainable RNA. The duration of S phase was five hours for cells with high RNAโ, six to nine hours for cells with moderate RNAโ and up to 27 hours for cells with minimal RNAโcontent.
The data suggest that the rate of progression the cell cycle of individual cells within a population may be correlated with the number of ribosomes per cell.