Fig 4.

Organic anion transport. Human proximal tubules formed on 2D surfaces are incubated for 20 hrs with the organic anions lucifer yellow (A, B; green), rhodamine 123 (C; red), 5,6-carboxyfluorescein (D; green) and BODIPY FL verapamil (E; green). Tubules are fixed before imaging, and the cell nuclei are counterstained with DAPI (blue). Part (B) shows an enlarged sector of the tubule displayed in (A). The arrowhead points to the outer layer of cells lining the tubular lumen, which displays only faint lucifer yellow fluorescence. By contrast, the lumen is strongly labelled. (C) Rhodamine 123 is enriched in the tubular lumen, as compared to the outer layer of cells. The arrowhead points to a region that is enlarged in the inset. The DAPI-stained nuclei of the outer cell layer are on the right in the inset. The cytoplasm displays only very faint rhodamine 123 fluorescence, which is enriched in the tubular lumen (on the left in the inset). (D) The small arrowheads point to the cytoplasm between the DAPI-stained nuclei of the outer cell layer. The cytoplasm displays only faint 5,6-carboxyfluorescein fluorescence. 5,6-carboxyfluorescein is enriched in the tubular interior (large arrowheads). (E) BODIPY FL verapamil is enriched in the cytoplasm of tubular and monolayer cells. Scale bars: 100 μm.