Inhomogeneities in glycoprotein cytochemistry of secretory granules in rat-parotid acinar cells after selective beta 1-adrenoceptor stimulation

Chronology of peroxidase activity in the developing rat parotid gland

The course of development of salivary peroxidase, an enzyme that has an important role in oral defense mechanisms, has been well documented in rat submandibular glands. However, the only report on salivary peroxidase activity in the other major salivary glands of the rat has been a cytochemical study of the adult parotid gland. In the present investigation, the accumulation of salivary peroxidase activity in developing parotid glands of rats was followed both biochemically and cytochemically. Specific activity (units per mg protein) attributable to salivary peroxidase began at 1 day after birth, then rose rapidly but unevenly, with peaks at 21 and 70 days, and no difference between the sexes at any age. Activity per gland increased progressively to 42 days in both sexes and was significantly higher in males at 70 days. The cytochemical observations on peroxidase activity localized to the rough endoplasmic reticulum and secretory granules of the developing acini were well correlated with the biochemical findings. Peroxidase-negative cells occurred in immature acini at 1 and 7 days, but only in the intercalated ducts thereafter. This observation suggests that the acini are a source of some of the ductal cells, at least during early postnatal development. The developmental pattern of specific activity differed from those of other rat parotid secretory enzymes, indicating that control of their synthesis during development is noncoordinate. The patterns of specific activity of the parotid and submandibular glands were complementary, suggesting that their combined secretions may supply biologically significant peroxidase activity to the oral cavities of rats throughout postnatal development.

Chronic treatment with beta adrenergic agonists and antagonists alters the composition of proteins in rat parotid saliva

This investigation was undertaken to determine the role of beta-adrenergic receptors in the regulation of the protein composition of rat parotid saliva. Chronic treatment of rats with dobutamine, a beta 1-adrenergic agonist, resulted in changes in parotid saliva volume, protein concentration, and composition which were essentially the same as those changes which occurred following chronic treatment with isoproterenol, a non-specific beta-adrenergic agonist. Chronic treatment with the beta 2-adrenergic agonist, terbutaline, had no effect on parotid saliva volume, protein concentration, or composition. Chronic treatment of rats with a beta 1-adrenergic antagonist, metoprolol, had different effects on saliva dependent on the manner by which the drug was delivered. Twice-daily injections of metoprolol led to a decrease in flow rate, but protein concentration and composition were unaltered. When metoprolol was delivered by surgically implanted osmotic minipumps, neither the flow of parotid saliva nor its concentration of protein was altered; however, there was a reduction in the proportion of proline-rich proteins in saliva. Comparable changes in parotid saliva protein composition occurred when the minipumps delivered propranolol, a non-specific beta-adrenergic antagonist. Chronic treatment of rats with an alpha 2-adrenergic agonist (clonidine) or antagonist (yohimbine) was without effect on parotid saliva flow rate, protein concentration, or composition. These findings suggest that the synthesis of proline-rich proteins is regulated, in part, by beta-adrenergic receptor stimulation, and primarily by the beta 1-receptor subtype.

Binding of wheat-germ agglutinin to glycoconjugates in the salivary glands of reserpinized rats

Salivary glands from adult rats that had received reserpine for 1, 3 or 7 days and from saline-treated controls were treated with rhodamine-labelled wheat-germ agglutinin conjugates (WGA-TRITC) to localize and characterize the distribution of glycoconjugates. Fluorescent and morphometric analysis of the parotid, submandibular and sublingual glands indicated that each gland responded differently to reserpine treatment. Parotid gland acinar cells and ducts showed no change in pattern or intensity of WGA-TRITC staining after reserpine. Mucous acinar cells of the submandibular gland had increased WGA binding and an accumulation of WGA-positive material in duct lumina after 3-7 days of reserpine. Morphometric analysis showed that the maximal increase in submandibular acinar-cell size occurred after 1 day of reserpine treatment. In sublingual glands, there was no detectable increase in mucous acinar-cell staining, but progressive accumulation of WGA-positive material was seen in duct lumina after 7 days of reserpine. As WGA binds to N-acetyl-glucosamine and N-acetyl-neuraminic acid residues, it may be that the eventual blockage of the duct system is related to increased production and secretion of glycoconjugates that contain these carbohydrates.