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

Age-related histomorphometric changes in labial salivary glands with special reference to the acinar component

PURPOSE

To evaluate histomorphometric age-related changes in labial salivary glands (LSG) of healthy subjects, with special reference to the mucous and seromucous acini.

METHOD

Investigation of age-related histomorphometric changes was conducted on 120 samples of LSG obtained from autopsy subjects free of salivary gland tumors/diseases. Samples were divided into young (< 30 years, n = 30), adult (30-60 years, n = 45) and old (> 60 years, n = 45) age groups. Measurements were performed on hematoxylin and eosin stained slides. Parenchymal components included acini and ducts. The acinar component was presently analyzed separately in respect to mucous acinar cells and seromucous acinar cells. Mucous acinar cells presented pale eosinophilic cytoplasm, while that of the seromucous was darker and basophilic. Stromal components included connective tissue, blood and lymphatic vessels, inflammatory infiltrate and adipose tissue. The mean volume fraction (V(v)) of all components in each age group was calculated. Statistical analysis was performed by one-way ANOVA and Tamhane tests.

RESULTS

The mean V(v) of the seromucous acinar cells decreased by 49.3% (p < 0.0001) and that of the mucous acinar cells decreased only by 28.5% (p = 0.0001). Changes in the ducts were statistically non-significant (p = 0.312). Of the stromal components, the mean V(v) of the adipose tissue showed the highest increase, 2768% (p < 0.0001) followed by the inflammatory infiltrate, 512% (p < 0.0001).

CONCLUSIONS

The marked decrease in the V(v) of seromucous acinar cells accompanied by a lower decrease in the V(v) of mucous acinar cells may explain age-related changes in LSG secretion. These findings could bear important implications regarding functional age-related changes of these glands.

Morphological features of the minor salivary glands

The minor salivary glands are important components of the oral cavity, present in most parts of the mouth, and their secretions directly bathe the tissues. Individual glands are usually in the submucosa between muscle fibres, and consist of groups of secretory endpieces made up of mucous acinar cells and serous or seromucous demilune cells. The ductal systems comprise intercalated ducts, intralobular ducts usually lacking basal striations, and excretory ducts opening directly through the mucosa Minor glands secrete highly glycosylated mucins, containing blood group determinants, and probably active in tissue lubrication and bacterial aggregation. They also secrete several antimicrobial proteins and immunoglobulins, and the lingual serous (von Ebner's) glands secrete digestive enzymes and proteins with possible taste perception functions. Minor gland morphology and function can conveniently be studied in the rat. There are substantial differences between major and minor salivary glands, as well as among the minor glands, in the nature and composition of their mucous and serous secretory products. The role of minor salivary glands in the function and defence of the oral cavity may be better understood as a result of new physiological and molecular methods applicable to samples of limited size and availability.

A review of electron probe X-ray microanalysis studies of salivary gland cells

Electron probe X-ray microanalysis (EPXMA) has now been successfully applied to several salivary gland preparations. This paper briefly reviews the principles underlying this technique and the specific sample preparation procedures which permit accurate measurement of elemental concentrations in the various intracellular spaces. Findings from salivary gland studies indicate that cytoplasmic and nuclear spaces of nonstimulated acinar cells have high concentrations of K and P, and low concentrations of Mg, Ca, and S; and that mature secretory granules have high concentrations of Ca and S, and relatively low concentrations of K and P. No consistent differences have been found between the elemental concentrations of mucous and serous secretory granules. In vivo and in vitro EPXMA studies of the elemental changes associated with secretory granule maturation indicate there are at least two stages in this process: an early stage during which granule S concentration increases in parallel with mass density as condensing vacuoles mature into secretory granules, and a late stage during which granule mass density and protein content increase with no further elemental concentration changes. Findings from other in vivo and in vitro studies indicate that secretory granule membranes are permeable to Na, K, and Cl ions because the granular concentrations of these elements are altered by electrochemical gradients. Recent EPXMA results indicate that cells stimulated with parasympathomimetic agonists have decreased K and Cl concentrations, and increased Na concentrations. Furthermore, the magnitude of these changes are quantitatively consistent with changes measured using radio-isotope equilibration and other techniques. In contrast, cells stimulated with the beta-adrenergic agonist, isoproterenol, have increased concentrations of Na and Cl, but unchanged K concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Histochemical and biochemical determination of calcium in salivary glands of cat

Although feline salivary glands have been used in investigations on secretion and microlithiasis and both processes involved calcium, nothing is known about its distribution in these glands. Therefore we have demonstrated the presence of calcium by a histochemical technique using glyoxal bis(2-hydroxyanil) and a biochemical technique using dry ashing. The histochemical technique stained serous acinar cells weakly and rarely found mucous acinar cells strongly in the parotid gland, mucous acinar cells moderately to strongly and serous acinar cells weakly in the sublingual gland, and central and demilunar acinar cells moderately to strongly in the submandibular gland. The biochemical technique revealed less calcium in the parotid than in the submandibular and sublingual glands. Both techniques revealed a decrease of calcium in submandibular and sublingual glands following parasympathetic stimulation. The histochemical distribution of calcium, which corresponds to that of acinar secretory glycoprotein, and the loss of calcium following parasympathetic stimulation, which causes release of secretory granules, indicate the presence of calcium in secretory granules. The concentration of calcium in the different types of acinar cell corresponds to the acidity of the secretory glycoprotein and suggests that calcium is present as a cationic shield to allow the condensation of polyionic glycoprotein in secretory granules.

Histochemical and biochemical determination of calcium in salivary glands with particular reference to chronic submandibular sialadenitis

Although salivary calcification is relatively common, little is known about the localization and content of the calcium of normal and diseased human salivary glands. We investigated this in chronic submandibular sialadenitis with a variable mixture of relatively normal and extremely atrophic parenchyma and in normal submandibular, parotid and palatal glands. Calcium was localized histochemically in mucous acinar cells of submandibular and palatal glands at moderate to high levels, in serous acinar cells of submandibular and parotid glands at low to moderate or occasionally high levels, in mucous ductal cells at moderate to high levels, and in extremely atrophic parenchyma at low levels or not at all. Calcium was determined biochemically at relatively high levels in the different glands in the order palatal, submandibular, sialadenitis and parotid. However, the differences were small. The results indicate that most salivary calcium is associated with secretory granules; this is the likely source of the calcium involved in salivary calcification.