Synthesis and secretion of glycoprotein in rat bulbo-urethral (Cowper's) glands. II. Modes of mucus secretion after stimulation by copulation.

Abstract

AbstractCopulation forced the mucous cells of rat bulbo‐urethral (Cowper's) glands to accelerate their secretion. Determination of macromolecularly‐bound hexose as a measure for the mucous contents of the glands and light and electron microscopic observations showed that the glands lost their mucus within four hours after the start of copulation. Secretion of the mucous granules occurred in an exocytotic fashion. This led to the formation of extensive secretory canaliculi extending to the cell bases. Successive mutual coalescing of the mucous granules formed intracellular secretion channels running from the secretory cell surfaces deeply into the cells.The vast reduction of cellular volume by loss of the numerous secretory granules and the sudden addition of large amounts of granule membrane to the cell membrane caused a considerable enlargement of the cell surface. The superfluous cell membrane was stored temporarily in tufts of long microvilli. The appearance of endocytotic structures and lysosomes was interpreted as indicative of internalization and breakdown of cell membrane. Between four and six hours after copulation cytoplasmic volume and size of RER and Golgi complex increased considerably, concurrently with increasing glycoprotein synthesis (Geuze and Slot, '76). During repopulation of the cells with mucous granules, luminal vesicles appeared close to the cell membrane between exocytotic pits. We suggest that the luminal vesicles originate by pinching off from microvilli and apical rims of cytoplasm overlying the mucous granules. Refilling of the glands was slow and took more than one week.