Regulation of P-glycoprotein activity by oxidative stress in isolated rainbow trout (Oncorhynchus mykiss) hepatocytes

To investigate the hypothesis that oxidative stress (OS) can regulate P-glycoprotein (P-gp) function in isolated rainbow trout hepatocytes (Oncorhynchus mykiss), cell suspensions were exposed in vitro to the pro-oxidant treatments diethyl maleate (DEM) or hydrogen peroxide (H2O2). Cellular glutathione (GSH) concentrations were depleted following treatment with 2.5 mM DEM and increased by treatment with 2.0 mM GSH. P-gp activity was assessed by measuring the accumulation of the P-gp substrate rhodamine 123 following treatment with either H2O2, DEM or GSH. Initial rates of R123 accumulation by hepatocytes treated with 0.025 to 2.5 mM DEM, 0.02 to 2.0 mM GSH, or 3 to 1200 µM H2O2 were not significantly different from their respective controls. The findings of this study suggest that P-gp activity in rainbow trout hepatocytes is not acutely modulated by increases in reactive oxygen species or changes in GSH content in vitro.