STRICT RELATIONSHIP BETWEEN DIALYZED SERUM CONCENTRATION AND CELLULAR LIFE-SPAN INVITRO

To determine the extent of the contribution of growth factor level on the life span of human diploid fibroblasts in vitro, the growth rate changes of IMR-90 cells under altered dialyzed serum (d-FBS) concentrations were investigated at different population doubling levels (PDL). As the PDL increased, the cells showed an accelerated requirement for d-FBS in order to maintain a constant growth rate, thus indicating a rapid loss of responsiveness of the cells to serum growth factors. A similar relationship was observed when the growth rate was extrapolated to zero and the cellular life span was predicted from this relationship. The cells cultured with 0.3% and 10% d-FBS ceased their growth at 54 and 76 PDL, respectively, while their predicted life span was 58 and 80-85 PDL, respectively. The cells cultured with 0.3% d-FBS responded poorly to an increase in the d-FBS concentration after entering phase III. These results suggest that the serum growth factor level is one of the determinants of cellular life span in vitro. © 1979.