Quantification of ATP‐producing and consuming processes of Ehrlich ascites tumour cells

Abstract

ATP production of Ehrlich ascites tumour cells was estimated on the basis of their coupled respiration and lactate formation. ATPconsuming processes were assessed from the effects of selective inhibitors of RNA synthesis, protein synthesis and proteolysis, Na+/K+-ATPase and CaZ+-ATPase on respiration. The extent of protein synthesis and proteolysis were also determined directly. From these values and those of the inhibition of respiration by selective inhibitors, a P/O ratio of 2.2 was calculated. About 75% of the total ATP consumption could be assigned to specific processes. The major ATP-consuming processes of tumour cells in an amino-acidenriched medium, in which they are in an approximate steady state, are protein synthesis with about 30% of total ATP consumption, and Na+/K+-ATPase with about 20%, while RNA synthesis, ATP-dependent proteolysis and Ca2+-ATPase contribute about 10% each. In an amino-acid-free glucose medium, protein synthesis is reduced to a third, with a corresponding decrease of respiration, whereas the rate of the other ATP-consuming processes is unchanged.Meyerhof was perhaps the first to demonstrate that consumption of ATP is a necessary requirement for continuous ATP production and a steady state of metabolism without accumulation of intermediary products in glycolysis [l]. The first accounting and balancing of ATP production and consumption on a respiring cell was made on the relatively simple metabolic system of rabbit reticulocytes [2], which lack DNA and RNA synthesis. It was found that about 70% of ATP consumption was accounted for by protein synthesis, Na+/ K + -ATPase and ATP-and ubiquitin-depending proteolysis. Therefore we proceeded to study a more complex cell, the Ehrlich ascites tumour cell, which is the object of the present report. Previously Racker et al. had performed a partial balance of ATP production and consumption on such cells [3]. They demonstrated that 50% of the ATP produced by phosphate-stimulated glycolysis may be consumed by Na+/ K+-ATPase. Since, however, even in tumour cells ATP is formed predominantly by oxidative phosphorylation, it appears necessary to estimate its contribution and also to take account of other ATP-consuming processes. We estimated ATP production from the coupled respiration and lactate formation. The extent of various ATP-consuming processes, i. e. protein synthesis, ATP-dependent proteolysis, RNA synthesis, Na+/K+-ATPase and CaZ +-ATPase, was assessed from the effect of selective inhibitors on coupled respiration. Protein synthesis and consumption were determined directly, thus permitting an estimate of the P/O ratio. MATERIAL AND METHODSThe Ehrlich tumour was propagated in female mice of the ICR strain by intraperitoneal transplantation. Tumour cells were obtained by peritoneal puncture 6-13 days after inCorrespondence to s.

Glycolysis in P‐glycoprotein‐overexpressing human tumor cell lines Effects of resistance‐modifying agents

“…This is a major ATP-consuming process when compared to other energy-requiring processes as estimated for Ehrlich ascites tumor cells on incubation in amino-acid-rich medium: about 30% for protein synthesis, 20% for Na+/K+-ATPase and approx. 10% for RNA synthesis, ATP-dependent proteolysis and Ca2+-ATPase [32].…”

Evaluation of the Antineoplastic Activity of L-rhamnose in vitro. A Comparison with 2-deoxyglucose

“…As Müller et al (22) showed for EAT cells, protein synthesis is an extremely energy demanding process. Thus, 2-DG which reduces the ATP production in tumor cells (9,42) was therefore expected to inhibit the protein synthesis.…”

Tumor Cell Metabolism Imaging

“…Warburg even hypothesized that cancer results from a defect of mitochondrial metabolism that leads to aerobic glycolysis (13). In some tumor cell lines, however, the total contribution of glycolysis to ATP production reaches only about 15% (14). Furthermore, human and rodent glioma cells have been shown to exhibit high or moderate susceptibility to inhibitors of oxidative phosphorylation (15), and glioma cells with a glycolytic phenotype oxidize pyruvate and glutamine when glucose levels are low (15).…”

“…In cancer cells, an anabolic pathway seems to dominate, which uses acetate for synthesis of fatty acids and lipids. In fact, 14 Cacetate has been used for many years to quantify fatty acid synthesis in vitro (128). Cell culture and animal studies have also supported that acetate uptake of cancer cells is related to fatty acid synthesis.…”