Belt-like gap junctions in the ductuli efferentes of some mammalian testes.

Cellular junctions of the lining epithelium of the efferent ductules of the mouse, guinea pig, and human testes were examined by freeze-fracture. A belt-like gap juncion consists of a large aggregation of particles with a few fragments of the tight junctional strands and circumferentially occupies the adluminal area between the nonciliated cells. This type of gap junction appears to be one of the components of the junctional complexes in mammalian efferent ductules. Functional significance of the belt-like gap junction is discussed in the light of the findings.