Distribution of microtubules and microfilaments in exocrine (ventral prostatic epithelial cells and pancreatic exocrine cells) and endocrine cells (cells of the adenohypophysis and islets of Langerhans). The relationship between cytoskeletons and epithelial-cell polarity.

We investigated the distribution of microtubules and microfilaments in some exocrine and endocrine cells in rats. Microtubules were stained by applying an immunofluorescent technique using antibodies against beta-tubulin, while microfilaments were stained with rhodamine-phalloidin, which binds selectively to polymerized actin filaments. In the cytoplasm of some exocrine cells (pancreatic acinar cells and ventral prostatic epithelial cells), the microtubules were distributed longitudinally from the apical region to the basal region, but no microtubules were found in the nuclear region. In exocrine cells, most of the microfilaments were localized beneath the apical plasma membrane. In some endocrine cells (those of the adenohypophysis and the islets of Langerhans), the microtubules exhibited a radial or reticular distribution in the cytoplasm, and intense fluorescence was observed in the perinuclear region. The immunofluorescence produced by the antibodies against beta-tubulin was more intense in endocrine cells than in exocrine cells. The microfilaments observed in the endocrine cells studied were homogenously distributed beneath the plasma membrane. Dot-like rhodamine-phalloidin staining was often observed in the cytoplasm of both the exocrine and endocrine cells. The present study clearly demonstrated marked differences in the distribution of cytoskeletal elements in exocrine and endocrine cells, and these may reflect differences in the secretory direction of such cells as well as in epithelial-cell polarity.