Cell surface distribution of fibronectin in cultures of fibroblasts and bladder derived epithelium: SEM-immunogold localization compared to immunoperoxidase and immunofluorescence..

Expression of cell surface fibronectin in cultures of untransformed fibroblasts is well documented, but little is known of its presence and distribution in cultured epithelial cells. Using species monospecific anti-fibronectin antibodies, the distribution of fibronectin in untransformed fibroblasts and in normal and neoplastic bladder epithelial cells was characterized by indirect labelling experiments using immunogold scanning electron microscopy (SEM). The surface matrix of fibronectin expressed in rodent and human fibroblast cell lines was demonstrated with ease by SEM of gold-tagged second antibodies. However, no fibronectin could be detected on any of the mouse and human bladder epithelium-derived cells studied in single or in mixed epithelial-fibroblast cultures. These SEM-immunogold observations were compared to and confirmed by immunofluorescence and immunoperoxidase microscopy. Immunofluorescence and SEM localization of the fibronectin in the extracellular matrix presented similar distribution patterns but the higher resolution of the SEM provided a more detailed analysis.