ASSESSMENT OF P-GLYCOPROTEIN-DEPENDENT DRUG TRANSPORT IN ISOLATED RATHEPATOCYTES USING RHODAMINE-123

To test the activity of P-170 glycoprotein in isolated hepatocytes, a method has been developed employing the fluorescent dye rhodamine 123 (R-123). The uptake of R-123 by both freshly isolated and 4-hr-plated hepatocytes depends on dye concentration, time of incubation, and cell number. The efflux of R-123 from cells is inhibited by sodium azide a nd by verapamil. In standard conditions the efficiency of efflux of R- 123 from cells correlates with the relative amount of immunoblottable glycoprotein. The method has been applied to detection of P-170 activi ty in hepatocytes from animals of different ages as well as from carci nogen-treated animals. The proposed assay appears a simple and adequat e tool for the functional assessment of multidrug transporter in liver .