Equivalent proliferation potential different size classes of human diploid fibroblasts

Human diploid fibroblasts were separated on the basis of size by sedimentation at unit gravity in a 5 to 30% fetal bovine serum gradient. The larger cells sedimented faster and were comprised of a larger proportion of cells that failed to incorporate tritiated thymidine during the 48 hours prior to sedimentation. However, the large cells and small cells had the same long-term replicative ability as determined both by ability to form large clones and by the total number of population doublings accrued in citro. Even after refractionation the larger and smaller cells had the same long-term proliferation ability. These results indicate that, although old cultures contain a high proportion of large cells and cells not able to synthesize DNA during a 24 to 48 hour period, these parameters cannot be used to select subpopulations of cells with different proliferative potentials from young or late passage cultures.