[Distribution of fibronectin on the surface of single fibroblasts. The possible mechanism of the assembly of fibronectin structures].

Distribution of fibronectin on the surface of lamelloplasm and endoplasm of single cultured mouse embryo fibroblasts was studied by means of indirect immunofluorescence technique. Large fibronectin fibrillae were located on the surface of endoplasm mainly, while "spots" and "streaks" of fibronectin dominated on the surface of lamelloplasm. Colcemid-treated cells had approximately the same distribution whereas cytochalasin B-treated cells were characterized by a spotty fluorescence alone. In contrast, in dense cultures of colcemid-treated cells fibronectin network underwent tearing, while it remained unchanged in cytochalasin B-treated cells. The centripetal movement of the fibronectin--receptor complexes along the cell surface from lamelloplasm into endoplasm (or the natural capping of fibronectin receptors) seems to play an important role in the assembling of fibronectin fibrillae.