Tubule-containing inclusions in the epithelial cells of the mouse epididymal duct.

The mouse epididymis, consisting of a head, body and tail, was examined by electron microscopy. The principal cells of the epididymal duct in the epididymal body have rod-shaped inclusions, 0.3 to 1.0 microns in diameter and 2 to 5 microns in height. The inclusions contain a bundle of tubules, about 40 nm in diameter, with a wall about 6 nm in thickness. The tubules are regularly arranged in a hexagonal pattern. A goniometric study of the inclusions shows evidence that the wall of the tubules consists of filament-like subunits which run parallel to each other and are inclined at about 25 degrees to the axis of the tubules, forming loose spirals. The inclusions occasionally contain material similar to that in the lysosomal bodies. These inclusions were observed in every epididymis examined, and seem to be related to the specific functions of the principal cells in the epididymal body.