Cytoskeletal markers allowing discrimination between brush cells and other epithelial cells of the gut including enteroendocrine cells.

Brush cells are specialised epithelial cells scattered throughout the simple epithelia of the respiratory and alimentary tracts. These cells have been suggested to serve a still unknown receptive function and use nitric oxide as a gaseous messenger molecule. At the light microscope level, brush cells can be identified by antibodies against the actin filament crosslinking proteins villin and fimbrin that not only stain the apical tuft of microvilli and their rootlets, but also label projections emanating from the basolateral surface of these cells. Since brush cells contain numerous intermediate filaments and microtubules and display a complicated basolateral cell morphology, we tested in this study whether antibodies against cytokeratin, tubulin and components of the membrane cytoskeleton might provide further markers for these cells at the light microscope level. Here we show that brush cells (identified by villin antibodies) can be discriminated from the neighbouring simple epithelium of the stomach, pancreatic duct and duodenum by particularly strong immunoreactivity with antibodies specific for cytokeratin 18. Tubulin antibodies reacted strongly with the upper half of brush cells in a pattern not observed in the other epithelial cells of these tissues, including enteroendocrine cells of the duodenum. Ankyrin, a protein that links the spectrin-based membrane cytoskeleton to integral proteins of the plasma membrane was revealed as a third cytoskeleton-associated protein, prominently expressed in brush cells where ankyrin is restricted to the basolateral membrane domain. The apparently high concentration of cytokeratin 18, tubulin and ankyrin in brush cells suggests that these cytoskeletal proteins might play a role in the mechanical stability and polarised organisation of these putative receptor cells.