Studies on the effect of ubiquinone on respiration of cultured cell (FM3A)

Abstract

To clarify the effect of exogenous ubiquinone on the respiration of FM3A cells, the amount of O2 consumption was determined by the Warburg manometer. On the other hand, properties of the cells in respiration were investigated from the point of Crabtree effect and electron-transport system in mitochondria. The results were as follows : Thirty min and 8 hr after addition of ubiquinone, the activity of respiration in the medium, from which L-phenylalanine and L-tyrosine were excluded, was not recovered, but apparent recovery of respiratory activity was observed 42-47 hr after the addition of ubiquinone. Endogenous respiration of FM3A cells was inhibited by the addition of 20 or 30 mM D-glucose, that is, Crabtree effect was observed. The FM3A cells can utilize succinate and NAD-linked substrate, glutamate, as the respiratory substrate, and the control of respiration was released by 2, 4-dinitrophenol (100 or 25 μM). The respiration in FM3A cells with succinate was almost completely inhibited by Antimycin-A (1 μg/ml) and 10-4M KCN. Respiratory control ratio was raised by repeated respiration with 200 μM ADP, but increase in ratio did not run parallel with ADP to O/P ratio. This was different from the results in HeLa cells.