Comparison of elemental concentrations in the acinar cells of the human labial salivary gland.

Two types of acinar cells were observed in human labial glands by conventional and analytical electron microscopic and light microscopic techniques. The predominant type contained large and prominent secretory granules that were strongly mucicarmine and PAS (with and without diastase) positive. The second type contained small, lacy, secretory granules, and these cells were faintly positive with these stains. The elemental contents of the two types of granules were measured by analytical electron microscopy using digital mapping and spot analysis applied to freeze-dried cryosections prepared from gland slices incubated in vitro under non-stimulated conditions. The large secretory granules had significantly higher Ca, S and Mg concentrations and significantly lower Cl and K concentrations than the small granules. The difference in elemental contents probably reflects differences in the content of secretory macromolecules. Specifically, the S content is thought to reflect the anionic properties of the secretory macromolecules, while the levels of divalent cations are thought to be determined by electroneutrality requirements for macromolecular folding and storage. No differences were found in nuclear or cytoplasmic elemental concentrations between the two cell types.