Fig 5.

The AMB-induced increase in endosomal pH in kidney cells is abolished by conjugation with AG. (A) Calibration curve of FITC-hTfn fluorescence intensity in MDCK-PTR9 cell endosomes as a function of pH. (B) MDCK-PTR9 cells were treated with AMB or AMB-AGC for 18 h, followed by 60 min of incubation on ice with 60 μg/ml FITC-hTfn to induce binding. After intensive washing, the cells were transferred to fresh medium and incubated at 37°C for 30 min to enable endocytosis. The samples were documented by confocal microscopy, and the pH was calculated as described in Materials and Methods. The columns show the average pHs (± the standard errors of the mean) of 145 to 170 endosomes in at least 16 different cells. One asterisk represents a P value of <0.0001 compared to the value for the no-drug control.