(a)
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Figure 4: Spontaneously formed 3D cysts are functional (see also Figure S4). (a) Representative fluorescence images at low magnification (a1) and high magnification (a2) demonstrate active transport of the fluorescent bile acid cholyl-lysyl-fluorescein (CLF) into the lumens of cysts. (b) Fluorescence intensity (FI) measurements along the red line in images from (a). (c) Representative fluorescence images demonstrating secretion of fluorescent rhodamine 123 (Rdm) into cyst lumens; secretions were inhibited by the Mdr1 inhibitor verapamil (Vrp), thus confirming that Mdr1 is functional. (d) FI measurements along the red line in the images from (c). (e) Mean intraluminal FI was normalized to background fluorescence in the absence (Rdm) or presence (Vrp) of verapamil; , measurements. Data are shown as ; (two-tailed Mann-Whitney test). (f) A representative low-magnification fluorescence image with varying FI in the lumens of cysts 1, 2, 3, and 4. (g) High-magnification image of that shown in (f); 1: strongly stained cyst (); 2: moderately stained cyst (); 3: weakly stained cyst (); 4: nonstained cyst (). (h) The bar graph of percentages of the four types of stained cysts demonstrates that Mdr1 function in cysts is inhibited by verapamil.