Ultrastructural and cytochemical study on the epithelium lining ductuli efferentes in Equus asinus.

The ultrastructure and cytochemistry of the epithelium lining ductuli efferentes in adult Equus asinus was studied. The epithelium is constituted of randomly distributed ciliated and non-ciliated cells extending from the basement membrane to the lumen. A third cellular type appearing to be in a degenerating state may also occur with variable frequency and is basally located. Mainly "non-ciliated cells" display ultrastructural and cytochemical features which can be related to strong resorptive activity; lysosomes and pigment granules, lipofuscinic in nature, are also present. Pigment masses exhibiting the same morphological and histochemical features fill the cytoplasm of degenerating cells. The results are compared with those obtained by previous authors in other Mammals and in Birds and are related to the functions commonly attributed to ductuli efferentes. The origin of degenerating cells, which are peculiar of Equidae, is discussed.