Extramitochondrial Fatty Acid Synthesis in Ehrlich Ascites Tumor Cells Propagated in Vitro and in Vivo 1

Abstract

Summary

The presence of extramitochondrial CO₂/HCO₃ ^- dependent fatty acid synthesis in Ehrlich hyperdiploid ascites tumor cells cultivated in vitro was demonstrated by the stimulatory effect of increasing CO₂ tensions (0-5% atm) on the ¹⁴C-acetate incorporation into hexane extracts of KOH hydrolysates of intact cells.

The incorporation of ¹⁴C-acetate into fatty acids of particle-free supernatants of Ehrlich ascites tumor cells propagated in vivo was shown to be dependent on NADPH regenerating systems, such as citrate-isocitrate, glucose or glucose-6-phosphate. The last two compounds, however, stimulated the ¹⁴C-acetate as well as the ¹⁴C-acetyl-CoA incorporation into fatty acids even in the presence of citrate-isocitrate + NADP. Under the same conditions fructose-1,6-diphosphate produced an inhibition of the acetate incorporation.

Determinations of the NADPH concentration of particle-free supernatants fortified with different NADPH generating systems showed that only glucose and citrate-isocitrate could stabilize the NADPH level, while fructose-1,6-diphosphate and pyruvate would lower or completely exhaust the NADPH content.

The mechanism of the stimulatory effect of glucose on acetate incorporation in particle-free supernatants is discussed.