The Journal of Cell Biology, Vol 89, 194-197, Copyright © 1981 by The Rockefeller University Press
Cell population heterogeneity in the inducibility of DNA synthesis in human diploid fibroblasts
MV Rao
The initiation of nuclear DNA synthesis has been studied in cytochalasin B
(CB)-induced binucleate human diploid fibroblasts (WI-38 cells). Mitotic
cells from different passage levels were rendered binucleate by a brief
pulse of CB. The cells were then washed free of the drug, and DNA synthesis
was studied by [3H]thymidine labeling. The results showed that, in a small
percentage of binucleate cells, one nucleus was labeled (S phase) and the
other nucleus was unlabeled (G1 phase). There was no significant difference
in the percentage of these cells with increasing passage levels. The
results of this study suggest that some WI-38 cells retire from the cell
cycle at different passage levels, and thereby become refractory to
inducers of nuclear DNA synthesis generated by sister cells in S phase.
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