When starved of a
carbon source, early passage normal cells such as chick embryo fibroblasts, human fibroblasts, mixed culture of splenic lymphocytes as well as "normal" cell lines (Nil or CHO cells grown as monolayer cultures) maintain their
ATP levels for 8 to 24 h at essentially those characteristic of cells fed
glucose. Several malignant or transformed cells (Py6, PyNil,
Ehrlich ascites tumor cells, CHO cells in
suspension and P388 lymphoblasts) exhibit a dramatic lowering in their
ATP within a few hours of the removal of
glucose. Normal cells exposed to
2-deoxy-D-glucose (2-DOG) in the absence of
glucose lose
ATP as rapidly as starved transformed cells. The loss of
ATP by transformed cells on
starvation is also accelerated by 2-DOG as is cell death.
2-deoxy-D-galactose (2-DOGAL) slows the loss of
ATP in
glucose starved transformed cells (growing as monolayer cultures) observed when the cultures are shifted to
sugar-free medium. Finally, normal cells in culture are able to maintain both their
ATP levels and their viability even after prolonged cultivation in a nutrient-free medium. Cultivation of malignant cells in a nutrient-free medium causes rapid loss in their
ATP, a phenomenon not preventable by the presence of
ouabain.