Fig. 8.

Intracellular Ca²⁺ promotes insertion of Mrp2 into the plasma membrane. (A) Representative HepG2 cell expressing rat GFPMrp2 and imaged by TIRF microscopy. The same cell is shown before and 15 minutes after addition of ATP (100 μM) to the bath. Yellow arrows indicated regions of increased fluorescence. Cells are pseudo-colored according to the scale at right. (B) Serial magnified images of the region indicated by the white square in (A) reveals progressive accumulation of GFP-Mrp2 in that region over time. Images are separated by 2-minute intervals. (C) Mean fluorescence increases in control cells, cells stimulated with ATP alone, or pretreated with Bapta-AM (50 μM). Note that there is a significant increase in GFP-Mrp2 membrane fluorescence in cells treated with ATP (124.9% ± 2.2%, n = 81 regions in 19 cells) as compared with control cells (106.7% ± 0.8%, n = 83; P < 0.0001) and that this increase is attenuated by pretreatment with BAPTA (112.9% ± 2.2%, n = 42; P < 0.001 by oneway ANOVA with Bonferroni post-test). Data represent the average of four independent experiments.