Membrane specialization in the rat epididymis. II. The clear cell

The clear cell is a characteristic cell type, particularly frequent in the epididymal tail, which has many small vesicles and larger vacuoles in the apical cytoplasm. In freeze‐fracture replicas of adult rat epididymis, we found that the limiting membrane (P‐face) of these vesicles and vacuoles, as well as the luminal plasma membrane (but not the basolateral membrane) contain a high density of prominent intramembrane particles. In contrast, the apical vesicles of the most common cell type, the principal cell, have a much lower density of particles, which are also of smaller size. The unique organization of these membranes in clear cells suggests that this cell type has a special role in epididymal function.