Electron microscopic characterization of intermediate filaments in rat liver parenchymal cells

Filamentous networks were isolated from rat liver and studied by electron microscopy after negative staining with uranyl acetate. Highly purified preparations of networks were used to obtain material for immunological studies, but morphological studies were made more satisfactorily on preparations purified only by sucrose density gradient centrifugation. The filaments forming the networks were 7 to 11 nm thick, consistent with classification as intermediate filaments. On immunofluorescence microscopy using antibodies directed against filament-forming proteins, both the networks in the isolated preparations and the filamentous networks in cryosections were visualized, thus providing evidence that the network isolated from rat liver homogenate corresponds to the network in intact parenchymal cells.