Energy metabolism and ATP turnover time during the cell cycle of Ehrlich ascites tumour cells

The energy production in different parts of the cell cycle due to aerobic and aerobic glycolytic metabolism and ATP turnover time was estimated by measuring the oxygen consumption, lactate-pyruvate and ATP content of Ehrlich ascites tumour cells growing in vivo. Cell fractions of high purity from the various parts of the cell cycle were obtained by means of elutriator centrifuging. The total energy production for one cell cycle was estimated to be 19 × 10^?12 mol ATP, 60% of which was due to the aerobic metabolism. Whereas the total ATP production is unchanged during G1 a fairly exponential increase is found during the S and G2 + M phases. The total cellular ATP content increases from 12 fmol ATP at early G1 to 28 fmol ATP at G2 + M; this increase, however, is discontinuous and is most pronounced during G1 and during late S phase S phase/G2 + M. The ATP turnover time, as defined as the ratio between ATP content and ATP production, was found to increase significantly from 75 sec in early G1 to 120 sec in late G1 but was constantly 100 sec during the early, middle and late S phase as well as G2 + M. These variations indicate maximum energy-requiring processes during early G1 period of the cell cycle and are discussed in relation to K⁺Na⁺ flux and macromolecule synthesis.