PH EFFECTS ON THE LIFE-SPAN AND TRANSFORMATION FREQUENCY OF SYRIAN-HAMSTER EMBRYO (SHE) CELLS

We have investigated the effects of modification of the growth media p H on Syrian hamster embryo (SHE) cellular lifespan and transformation. Culturing SHE cells in Dulbecco's modified Eagle's medium (DMEM) at p H 6.7 relative to pH 7.3 results in a 4-fold increase in the lifespan of SHE cells before senescence occurs, This effect was observed both w ith the wild type SHE cell population and with the morphological trans formation sensitive subpopulations derived from the wild type SHE cell mixture (cl9 and cl17), The increase in SHE cell lifespan at pH 6.7 w as observed both as an increase in days in culture and an increase in the number of total population doublings before cellular senescence oc curred. The tumor promoting agent TPA increased the lifespan of the SH E cell population and one of the MT sensitive subpopulations when thes e cells were cultured in pH 7.3 medium, Interestingly, treatment of th e SHE cell population, and the two MT sensitive SHE cell clones with T PA at culture medium pH of 6.7 reduced the lifespan of each cell type, Finally, culturing SHE cells in medium of pH 6.7 increased the potent ial of the cells to undergo morphological transformation in response t o treatment with carcinogens, demonstrating a potential connection bet ween SHE cell lifespan and carcinogen induced morphological transforma tion, probably through a mechanism involving a pH induced block in cel lular differentiation, We believe this is the first report demonstrati ng the role of pH in controlling cellular lifespan.