Cytological response of the principal cells in the initial segment of the epididymal duct to efferent duct cutting in mice.

The principal cells in the initial segment of the mouse epididymal duct were observed by light and electron microscopy over a period from 6 h to 4 weeks after efferent duct cutting. These were compared with the cells in Segment II (the segment next to the initial segment), in order to understand the functional differentiation of both segments. In the initial segment, a large number of the principal cells were degenerated and disappeared within 2 days after the operation. The remaining epithelial cells rapidly decreased in height as the degeneration proceeded and the principal cells were light- and electron-microscopically transformed into the cells similar to the principal cells in Segment II. The principal cells in Segment II showed no changes after efferent duct cutting. The findings suggest that the principal cells in the initial segment have a secretory potentiality of Segment II cells, which is normally latent but becomes manifest after the efferent duct interruption that removes the absorptive function of the testicular fluid.