Relationship between cell kinetic changes and metabolic events during cell senescence in vitro.

Cell kinetic studies performed throughout the lifespan of fibroblasts with a limited lifespan in vitro have led to the conclusion that although division slows down, almost all cells are able to divide until the last subcultivation. The prolongation of the division cycle is primarily due to the impariment of mechanisms preceding DNA synthesis and mitosis. An attempt was made to distinguish between primary and secondary changes and to correlate the findings concerning cell kinetics with alterations observed at the molecular level. A decline in protein synthesis was the first modification detected. The two parameters that are always present during cell senescence in vitro, i.e., and increase in cell volume and a decrease in saturation density could be due respectively to a change in cell permeability and a decline in ribosome synthesis. The latter could also be the step responsible for the limited potential of division.