Immunocytochemical localization of amylase in the parotid gland of developing and adult rats.

An antiserum against purified rat parotid amylase was used to localize the protein in parotid glands of developing and adult rats. The unlabeled antibody peroxidase-antiperoxidase method and the protein A-gold colloid technique were used at the light and electron microscope levels, respectively. Immunoreactive amylase was detected in a few scattered cells in the glands of 2-day-old rats. During the following days the number of cells stained immunocytochemically for amylase increased rapidly; at 15 days of age all acinar cells revealed amylase, but the intensity of immunostaining varied from cell to cell. Electron microscopically, amylase was localized in the secretory granules, and by using a more concentrated antiserum, in the rough endoplasmic reticulum and Golgi complex. At early stages of development the acinar cells contained fewer and smaller secretory granules than in adult animals; the gold particles indicative of amylase were randomly distributed over the secretory granules. In the glands of adult rats, amylase was distributed inhomogeneously within the secretory granules. In the majority of secretory granules gold colloid particles were located over the electron-dense portions of the granules. However, secretory granules in which an amylase-rich shell surrounded an amylase-poor or amylase-negative "core" were not infrequent.