Density-dependent survival of Ehrlich ascites tumour cells in the presence of various substrates for energy metabolism.

We have found that Ehrlich ascites tumour (EAT) cells, deprived of any carbon source, and suspended at a density of 2 X 10(5) cells/cm3, begin to die only after 12 h of starvation, though it is known that under these conditions they lose over 80% of their ATP within 30 min. Moreover, we have found that the viability of the cells incubated in the absence of any substrate for energy metabolism is strongly dependent on the density of the cell suspension, and can be significantly improved simply by increasing the suspension density. This prompted us to investigate the density dependence of the maintenance of EAT cell viability in the presence of various substrates for energy metabolism and metabolic intermediates. It was found that: Glucose ensures 48 h viability of EAT cells irrespective of suspension density. Fatty acids and pyruvate as sole carbon source do not improve EAT cell survival. In the presence of glutamine as sole carbon source the EAT cell survival shows dependence on cell-suspension density. At densities of 1.6 X 10(6) to 3.2 X 10(6) cells/cm3 the cell viability is maintained at least as well as in the presence of glucose, but at low cell-suspension densities glutamine does not support cell viability. In the presence of glutamine, addition of 1 mM-inosine and 1 mM-uridine ensures high cell survival irrespective of the cell-suspension density. In the presence of inosine or uridine (10 mM) as sole carbon source, the EAT cell survival is the same as in the presence of glucose and does not depend upon cell-suspension density. Guanosine is less effective, whereas adenosine has no effect at all on the maintenance of EAT cell viability for 48 h. There is no correlation at all between EAT cell survival and the rate of lactic acid production. At a cell-suspension density of 1.6 X 10(6) cells/cm3 the cell survival is of the same order in the presence of glutamine as in the presence of glucose, in spite of the fact that in the first case the rate of lactic acid production is more than 20 times lower. There is no correlation between the capacity of particular nucleosides to support EAT cell survival and their effects on glycolysis and oxygen consumption.