IMMUNOELECTRON MICROSCOPIC LOCALIZATION OF FIBRONECTIN IN CULTURED HUMAN KERATINOCYTES

We investigated the ultrastructural localization of fibronectin (FN) i n cultured human keratinocytes using an improved method of peroxidase- immunoelectron microscopy. This method enabled us to visualize the pre cise localization of FN within the cells while preserving the morpholo gy. FN was localized in the protein synthetic and secretory organelles , including the rough-surfaced endoplasmic reticulum, Golgi complex, m ultivesicular bodies and perinuclear space. It was also detected in th e extracellular space, on small regions of the villous projections of cell membranes at the site of secretion and at cell-substratum contact sites. These findings confirm that human keratinocytes synthesize, se crete and deposit FN in the pericellular matrix.