IMMUNOFLUORESCENCE MICROSCOPIC STUDY ON THE CYTOSKELETAL FILAMENTS IN THE SEPARATED SUPERFICIAL CELLS OF RAT URINARY-BLADDER EPITHELIUM

We observed by immunofluorescence microscopy the distribution of cytoskeletal filaments in the superficial cells (SP cells) of rat urinary bladder epithelium in a distending state. To precisely detect SP cell fluorescence, the cells were separated from the distended bladder epithelium by scraping with a glass slide after paraformaldehyde fixation. Each cell appeared characteristically polygonal and flattened. In these cells, F-actins were predominantly distributed at the lateral cell border, marking the cell boundary. They also formed fine networks in the inner cytoplasm. Cytokeratin filaments were distributed in two characteristic patterns: they marked cell boundaries as did F-actin, and they formed thick circular bundles between the nucleus and cell margin. These two types of keratin filaments were also connected by thin filaments. These cytokeratins contained at least cytokeratin 18 subunit. Numerous microtubules were distributed evenly in the cytoplasm forming fine networks, except near the cell periphery. These observations show that SP cells are supported mainly by cytokeratin networks.