FORMATION OF EXTRACELLULAR ADENOSINE TRIPHOSPHATE BY TUMOUR CELLS

The formation of extracellular ATP by Ehrlich ascites tumour cells and HeLa cells was studied. The tumour cells were incubated with the substrates, including 32P‐labelled inorganic phosphate, and cofactors of the glyceraldehyd‐3‐phosphate dehydrogenase and phosphoglycerate kinase reactions (complete system), as well as with an incomplete system lacking ADP, NAD+ and glyceraldehyde‐3‐phosphoric acid. All incubations were performed under isotonic conditions. After 1 min incubation of tumour cells, an 8‐fold increase in the 32P‐labelled ATP took place with the complete system, compared with the incomplete system. All the (32P)ATP formed as a consequence of the presence of the phosphorylated substrates and cofactors in the complete system could be recovered in the extracellular medium. No measurable leakage of intracellular (32P)ATP into the extracellular medium occurred. The extracellular medium did not contain significant amounts of solubilized enzymes responsible for the extracellular formation of (32P)ATP. The presence of intact tumour cells during incubation was necessary for the main part of (32P)ATP to be formed. It is therefore concluded that most of the (32P)ATP present in the extracellular medium was formed by enzymes located on the surface of the tumour cells. © 1969 Scandinavian Physiological Society