Ultrastructural characteristics of tuft cells in mouse gallbladder epithelium

Mouse gallbladder was fixed by perfusion or immersion in glutaraldehyde and/or osmium tetroxide for electron microscopy. Besides usual columnar epithelial cells there were infrequent tuft cells in the epithelium. The cells rested on the basal lamina and extended to the gallbladder lumen. The microvilli on the apical cell surface were tall and thick and there was a rich network of microfilaments radiating from the core of the microvilli to the apical and juxta-nuclear cytoplasm. Among the bundles of microfilaments there were vertically oriented microtubules in the apical cytoplasm. Although the function of the tuft cells in the gallbladder epithelium remains unknown, it is proposed that their unique morphology may reflect a specialized resorptive function involving motility of microvilli and other cell organelles.