Ultrastructure of the parotid gland in the common vampire bat, Desmodus rotundus, with special emphasis on oncocytes.

The parotid gland of the common vampire bat, Desmodus rotundus, is a pure seromucous gland. Typical acinar cells have a complement of secretory granules with a light matrix and one or several spherules and ancillary densities. These cells also contain mitochondria of conventional appearance. Mixed in with these acinar cells are cells that fulfil all of the ultrastructural criteria for identification as oncocytes. They contain enhanced numbers of mitochondria that frequently display peculiarities in the number and disposition of their cristae. The oncocyte mitochondria are closely packed and often are joined by periodic bridges. Most of the cells in the intercalated ducts are cytologically unremarkable; a few scattered duct cells have a single, grossly distended cisterna of rough endoplasmic reticulum that contains a homogeneous material of moderate density. The intercalated ducts are succeeded by ducts that lack the usual basal striations, but that consist of cells with numerous, small, dense granules. These secretory ducts probably are the homologues of striated ducts in parotid glands of other species. The structure of these ducts in the parotid gland in the vampire bat suggests that this gland does not play a homeostatic role in the regulation of electrolytes, a role that appears to be carried out in this bat in the submandibular glands, but that its major intralobular ducts contribute substantial quantities of organic material to the saliva.