Fine structure of the prostatic epithelium of the opossum (Didelphis virginiana Kerr)

The opossum prostate is highly complex cytologically, containing six different secretory cell types, each possessing a recognizably different secretory product. Secretory granules in cells of the first segment contain numerous particles 60 Å in diameter of high electron density. They are transferred to the lumen by apocrine secretion. Both granules and lumina contain iron (Turnbull blue reaction). Segment two possesses three cell types. Type A cells have spherical secretory granules containing acid mucopolysaccharides. In type B cells, secretory granules are elongate and possess densely packed protein filaments, 80 Å in diameter. Secretory granules in type C cells contain crystalloids of hexagonally packed cylinders with a spacing of 600 Å. Third segment cells contain few organelles and have a broad irregular microvillar border. Most of the cytoplasm is filled with glycogen particles. The secretion is apocrine. The lumen contains lipoprotein lamellae, probably derived from shed microvilli, and also membrane bound glycogen globules originating from the cytoplasm. The contents are positive for acid, di‐ and tri‐phosphatases and peroxidase. Catalase activity in the third segment is unusually high.