Detection of close association of cav-1 and cav-2 in epithelial cells by double-labeling indirect immunofluorescence and FRET in tissue sections of the rat trachea and large bronchi. Images of donor (cav-2 labeled with Cy3-conjugated secondary antibody, A-B) and acceptor (cav-1α labeled with Cy5-conjugated secondary antibody, C-D) fluorescence. Cy5 was bleached in a region of interest 1 (compare ROI 1 in C and D). E: ΔIF for each ROI. ROI 1: bleached area (compare C and D). ROI 8: freehand encircled region of the basolateral plasma membrane of the epithelial cells in bleached area. ROI 2–7: control areas outside the bleached area. F: ΔIF in the area of the basolateral membrane in experimental group (4 animals) compared to control group. *** p ≤ 0.001, Mann-Whitney test. n = number of measurements. Boxplots: percentiles 0, 25, median, 75, 100.