TABLE 3.
Uptake of folate and MTX in the presence of varying concentrations of inhibitor
The standard assay mixture was modified to contain [S] ≅ Km and corrected for additional DMSO (0.4%). IC50 was calculated by fitting to a two-parameter IC50 equation. ND = not determined.
| Substrate | IC50 against folate | IC50 against MTX | Km | Vmax | Calculated IC50 |
|---|---|---|---|---|---|
| μm | μm | μm | pmol s−1 (108 cells)−1 | μm | |
| Methotrexate | 3.4 ± 0.4 | 16.5 | 0.68 | 2.2 | |
| Folic acid | 1.9 ± 0.4 | 2.07 | 0.19 | 2.9 | |
| 5-Methyl-THF | 6.3 ± 1.0 | 8.0 ± 0.8 | |||
| pABA-Glu | 30.8 ± 3.7 | 33.5 ± 4.6 | |||
| Pemetrexed | 3.2 ± 0.3 | ND | |||
| Raltitrexed | 1.8 ± 0.4 | ND |