Regional variations in endoplasmic reticulum in the vas deferens of normal and vasectomized rats

The fine structure of the epithelium of different parts of the rat vas deferens was studied in normal rats and at intervals of up to nine months after vasectomy. The cytology of the columnar epithelial cells showed regional variations particularly in the type and extent of endoplasmic reticulum. Cells of the proximal part of the vas deferens were characterized by basal and perinuclear granular endoplasmic reticulum, a large Golgi apparatus, and numerous apical microvilli, vesicles, and vacuoles. In contrast, the columnar cells of the distal portion of the vas deferens contained large amounts of smooth endoplasmic reticulum, much of which assumed the form of large whorls of smooth membranes. In the distal segment the number of microvilli, vesicles, and vacuoles was less but mitochondria were more numerous than in the proximal part. Cells in the middle portion of the vas deferens showed some features of both proximal and distal parts. These structural characteristics, along with previous experiments, suggest that in the proximal portion of the vas deferens absorption of material from the lumen is an important function, while the cells of the distal part may synthesize steroids. Thus, these regional differences in ultrastructure probably reflect regional differences in function along the length of the vas deferens. After vasectomy the regional specializations were retained and did not appear to be altered. The possibility that this structural and functional sequence is significant for normal fertility and its relation to attempts to reconnect the vas deferens after vasectomy are considered.