Intracellular drug activity and bioactivation enzymes vary among resistant cell lines
| . | CEM/wt . | CEM/CdA25 . | CEM/CdA100 . | CEM/CdA1000 . |
|---|---|---|---|---|
| CdATP formation (μM) after 12-h incubation with 1 μM CdA | 7.6 ± 0.6 | 4.5 ± 0.4 | 3.7 ± 0.6 | ND |
| dCK activity (pmole/mg/min) | 245 ± 18 | 204 ± 5 | 142 ± 14 | 4 ± 1 |
| dGK activity (pmole/mg/min) | 313 ± 24 | 428 ± 48 | 502 ± 4 | 426 ± 15 |
| . | CEM/wt . | CEM/CdA25 . | CEM/CdA100 . | CEM/CdA1000 . |
|---|---|---|---|---|
| CdATP formation (μM) after 12-h incubation with 1 μM CdA | 7.6 ± 0.6 | 4.5 ± 0.4 | 3.7 ± 0.6 | ND |
| dCK activity (pmole/mg/min) | 245 ± 18 | 204 ± 5 | 142 ± 14 | 4 ± 1 |
| dGK activity (pmole/mg/min) | 313 ± 24 | 428 ± 48 | 502 ± 4 | 426 ± 15 |
Levels of CdATP were quantitated by high-performance liquid chromatography as described in “Materials and methods” after cells were incubated in the presence of 1 μM CdA for 12 hours. Enzyme activity of dCK and dGK was measured in extracts made from sensitive and resistant cells. Radioactive CdA was used as a substrate to measure both dCK and dGK activities. In the case of dGK enzyme activity, measurements were conducted in the presence of excess (1 mM) deoxycytidine to block dCK enzyme activity. The specific activities of dCK and dGK are expressed in picomoles per milligram of protein per minute. Data shown are from 1 typical experiment performed 3 times in duplicate.
ND indicates not detectable.