Control of glycolysis and the pentose phosphate shunt in transformed 3T3 cultures rendered permeable by ATP.

Exogenous ATP has been shown earlier to activate a permeability change in transformed 3T3 cultures leading to massive efflux of the acid-soluble pools. This leads to reduction of the basal rate of glycolysis to a very low level so that glycolysis becomes almost totally dependent on the addition to the medium of glucose, inorganic phosphate and ADP in order to restore the rate to that of untreated cells. No such depression of glycolysis is observed in untreated transformed cells or in ATP-treated normal 3T3 cells. In such permeabilized cultures, phosphorylated intermediates such as glucose-6-phosphate and fructose-1,6-diphosphate can serve as effective substrates for lactic acid formation. ATP treatment of cultured cells also allows molecules as big as NADP to enter the cells and participate in the pentose phosphate shunt pathway. This ability to temporarily and differentially render transformed cells permeable allows a review of several aspects of cellular metabolism and biosynthesis in the intact cell where the cellular organization is maintained. Furthermore, it deserves serious consideration as a means to achieve differential cytotoxicity of transformed cells by chemotherapeutic agents which, on their own, are indiscriminate in their action.