Fig. 4.

Fluid-phase markers are not enriched in Rab11a-positive compartments in MDCK cells. Filter-grown MDCK cells (top) or PTCs (bottom) expressing S-nitroso-N-acetyl-penicillamine (SNAP)-Rab11a were labeled with tetramethylrhodamine (TMR)-Star and incubated with apically added FITC-dextran (1 mg/ml) for 20 min, fixed, and then examined by confocal microscopy. In contrast to the readily observed accumulation of dextran in Rab11a-positive compartments in PTCs, dextran has little access to this compartment in MDCK cells. Scale bar, 7.5 μm.