ATP-dependent, P-glycoprotein-mediated efflux of xenobiotics is an important cellular defense strategy, preventing intracellular accumulation. Studies have shown that costs associated with cellular defense may be substantial however; few studies have examined costs associated with P-gp transport. Therefore, the activity and energetic costs associated with P-gp transport examined in trout hepatocytes. Accumulation and efflux of doxorubicin was concentration dependent, and tariquidar significantly inhibited efflux by 57%, 61%, and 50% in the 125, 75, and 25 μM groups. P-gp efflux of doxorubicin significantly reduced intracellular ATP concentration, adenylate energy charge, and phosphorylation potential with highest percent decreases of 25%, 11%, and 53% respectively, and increased concentrations of ADP, AMP, and Pi with highest percent increases of 26%, 36%, and 11% respectively compared to controls and tariquidar-treated groups. These results indicate that exposure of hepatocytes to DOX caused an increase in P-gp activity which was shown to affect cellular energetics.
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