A. Representative photomicrographs illustrating double immunofluorescence localization of ErbB1 and SSTR1-5 in MCF-7 cells. Localization of ErbB1 (red staining) was visualized using monoclonal antibodies with Cy3-conjugated goat anti-mouse IgG (a-e). The same cells were incubated with polyclonal SSTR1-5 antibodies and visualized (green staining) using FITC-conjugated goat anti-rabbit IgG (f-j). Colocalization of ErbB1 and SSTR1-5 was determined by merging individual red and green images to give orange-labelled cells (k-o). All receptors are expressed as membrane and cytoplasmic protein. Arrows indicate colocalization at the cell surface. Scale bar = 25 μm. B. Quantitative analysis of MCF-7 cells showing colocalization of ErbB1 with SSTR1-5. Cells expressing two receptors together were counted from at least 8 randomly selected vertical and horizontal fields from each coverslip. Data are from three different experiments performed in duplicate and are presented as mean ± SEM for each receptor combination. C. Quantitative analysis of cells showing ErbB1 and SSTR1-5 in distinct locations within the same cell. Data were analyzed as described in B.