Figure 3.

PKA activity in the parental and taxol resistant cells before and after treatment with taxol. PKA activity was determined using the Pierce Colorimetric Assay Kit that utilizes a fluorescent-labeled Kempeptide (a PKA-specific peptide (LRRASLG) substrate). Untreated and taxol treated cells were homogenized in a Dounce homogenizer (10 strokes with a tight fitting pestle) in a buffer containing 25 mM Tris-HCl, pH 7.4, 0.5 mM EDTA, 0.5 mM EGTA, 10 mM DTT and protease inhibitor cocktail. The homogenate was centrifuged at 13,000 × g for 20 min and the PKA activity was measured (in triplicate) in the supernatant fraction. Values shown are mean ± SD of 3 separate experiments.