Vesicles in rat epididymal fluid. Existence of two populations differing in ultrastructure and enzymatic composition

Glycosidase activity is very high in rat epididymal fluid as a consequence of the secretory capacity of the epithelium. The mechanism of this secretion is, so far, unknown. Membrane-bound vesicles with activity of beta-galactosidase and N-acetyl-beta-D-glucosaminidase were previously isolated by us from rat epididymal fluid. We report here the existence of two populations of epididymal vesicles separated by centrifugation in a sucrose gradient. They were found to differ in isopicnic equilibrium, size, ultrastructure, and enzymatic activity. Seven days after castration the protein content and specific activities of both enzymes were found decreased in the fractions containing the vesicles. A role in enzyme secretion by the epididymal epithelium is suggested for each vesicle population.