Membrane structural specialization of the toad urinary bladder revealed by the freeze-fracture technique. II. The mitochondria-rich cell.

Examination of the toad urinary bladder by freeze-fracture electron microscopy reveals that the mitochondria-rich cells of the epithelium possess distinctive and characteristic membrane structural specialization. Unique rod-shaped intramembrane particles are found in luminal and basal membranes as well as certain intracellular vesicles of this cell type. The consistent findings of two discrete patterns of luminal membrane structural organization supports the possibility that two morphological forms of mitochondria-rich cell exist within the toad bladder epithelium.