Mechanism and control of degradation and resynthesis of adenylates in tumour cells.

A comparative study revealed that Ehrlich ascites carcinoma (EAC) cells use glutamine plus inosine for regeneration of adenylates via the purine nucleotide cycle, whereas AS 30D hepatoma cells use adenosine instead. This observation can be correlated with the very low production of aspartate from glutamine in hepatoma cells. Although glucose is an important energy fuel for EAC, it cannot maintain a high enough level of adenylates unless glutamine is also present. Kinetic analysis of hydrolysis of ATP and ADP in the presence of rotenone suggests that deamination of AMP does not maintain a high enough ATP/ADP ratio and probably does not act as energy buffer after inhibition of cell respiration. It seems that, compared with normal cells, malignant cells have the ability for a very rapid regeneration of adenylates. It is proposed that instability of the adenine nucleotide pool, owing to frequent aerobic-anaerobic transitions, represents an essential feature of neoplasia, with profound impact on the whole metabolism of tumour cells.