X-ray microanalysis applied to the study of salivary glands

X-ray microanalysis can be used to study the distribution of elements in salivary glands at the cellular and subcellular level in a variety of physiological and pathophysiological conditions. The acinar cells of the adult rat and mouse submandibular gland contain high concentrations of calcium due to the presence of calcium-rich secretory granules. The calcium concentration of the acinar cells can be increased under a variety of pathophysiological conditions, e.g., in animal models for cystic fibrosis, due to an increase in the number of secretory granules and changes in their calcium-binding properties. Cholinergic stimulation results in a decrease in the concentrations of Cl and K in all cell compartments in adult animals, but not in newborn rats. Also the secretory granules in the glands in adult animals lose Cl and K, indicating that ion (and water) transport mechanisms may be present in the membrane of the granules. During chemical fixation, the secretory granules in the adult glands swell and their morphology is different from that in freeze-substituted glands. The characteristics of the secretory granules in the acinar cells of newborn rats are different from those of adult animals.