[Regional differences of the clear cells in the mouse epididymal duct: a histological study].

Age-related changes in the clear cells and responses of the clear cells after ligation at the efferent duct or the junction between the epididymal head and tail were examined by light and electron microscopy with special reference to the regional differences in the epididymal duct in mice. In adult mice, the epididymal duct is divided into five segments (I-V) and the lumen distal to Segment II contains PAS-positive material in addition to spermatozoa. The clear cells had vacuoles and PAS-positive granules containing acid phosphatase. Electron microscopy suggested that the clear cells ingest the luminal material and condense it into the PAS-positive granules in the basal cytoplasm. The clear cells first appeared at 20 days of age following appearance of the PAS-positive material in the lumen. After 40 days, the clear cells became frequent and well-developed containing much PAS-positive granules in the distal Segment IV and Segment V, which were filled with abundant spermatozoa and PAS-positive material. After ligation at the efferent duct, the duct distal to Segment II was filled with PAS-positive material but no spermatozoa, and the clear cells in the proximal Segment V became to contain more abundant and large PAS-positive granules. After ligation at the junction of the epididymal head and body, the luminal PAS-positive material was scarecely seen in Segment IV but densely in Segment V and the clear cells were more developed in the distal Segment IV. The findings suggest that the clear cells are especially developed to absorb the luminal PAS-positive material in the distal region of the epididymal duct and may absorb different PAS-positive material in different segments.