FIG. 3.

Intracellular PGK activity in the metabolism of 4′-Ed4T in Tet-On PGK RKO cells. (A) Expression of PGK in Tet-On PGK RKO cells, as detected by Western blotting. APE-1 was used as the internal control. (B) Doxycycline-induced PGK RKO cells (5 × 10⁵) were incubated with 2 μM [5′-³H]4′-Ed4T (478 mCi/mmol) for 16 h. Cell extracts were prepared and subjected to HPLC analyses. The detected radioactivity was calculated as picomoles of each type of metabolite of 4′-Ed4T analog/10⁶ cells for each doxycycline concentration. (C) Total amounts of di- and triphosphate metabolites formed. Each value is the mean ± standard deviation from three independent experiments.