[Comparison between the succinate dehydrogenase inhibition test and ATP assay for in vitro chemosensitivity testing]

The predicted level of cell viability was compared between the succinate dehydrogenase inhibition (SDI) test and the adenosine triphosphate (ATP) assay, both of which are used for in vitro human tumor chemosensitivity testing. After HeLa cells had been exposed to various concentrations of 5-FU for 1, 2, 3 or 4 days, the decrease occurring in viable cell number correlated with that of succinate dehydrogenase (EC 1.3.99.1) activity and that of the intracellular ATP level of the viable cells. In dead cells, the ATP level was extensively decreased, but the succinate dehydrogenase activity remained at a level of 11% of that of 5-FU-untreated viable cells, even on day 4. The cell viability correlated well with the intracellular ATP level, as compared with the succinate dehydrogenase activity. The activity remaining in dead cells must thus be taken into consideration for the prediction of chemosensitivity in the SDI test, but not in the ATP assay.