The effects of oxymetazoline on secretion of protein and some electrolytes by rat submandibular and parotid glands

Oxymetazoline is a potent secretagogue for the salivary glands of rats. In the parotid gland, it activates preferentially alpha-adrenoceptors. As for the submandibular glands, it activates alpha-adrenoceptors at relatively low doses but at higher doses it allows secretion of new types of proteins.     

Parasympathetic degeneration secretion of saliva in rats.

In rats under chloralose anaethesia saliva was found to flow from the submandibular and parotid glands previously subjected to (partial) postganglionic parasympathetic denervation. Secretion started in the submandibular glands 8.8-11.8 hours, and in the parotid glands 14.0-12.6 hours after the denervation and lasted about 7 hours in both glands. It was not abolished by sympatholytic drugs but by atropine. It is regarded as an example of the "degeneration activity" described in many organs and species and provides a method for prolonged stimulation of salivary glands in rats.     

Acinar cell response to liquid diet during rats’ growth period differs in submandibular and sublingual glands from that in parotid glands

Continuously feeding a liquid diet to growing rodents strongly inhibits parotid gland growth, due to suppressed growth of acinar cells. This study investigated whether a liquid diet had a similar effect on submandibular and sublingual glands of growing rats. Rats were weaned on day 21 after birth and then fed a pellet diet in the control group and a liquid diet in the experimental group for 0, 1, 2, 4, and 8 weeks. Their submandibular and sublingual glands were excised, weighed, and examined histologically, immunohistochemically (using antibodies to 5′-bromo-2-deoxyuridine and cleaved caspase 3), and ultrastructurally. The submandibular glands did not significantly differ between the control and experimental groups at all tested points. Only at Week 8, acinar cell area and 5′-bromo-2-deoxyuridine-labeling index of acinar cells in sublingual glands were significantly lower in the experimental group than in the control group. These results show that a liquid diet during rats’ growth period had no effect on acinar cells in their submandibular glands, and only a slight effect on acinar cells in their sublingual glands of growing rats, in contrast to the marked effect of a liquid diet on parotid glands.     

Isoprenaline-induced changes in rat parotid and submandibular glands are age- and dosage-dependent.

Neonatal rats treated with chronic injections of isoprenaline (isoproterenol) for 10 days revealed differential induction of proline-rich proteins and glycoprotein synthesis between the parotid and submandibular glands. Biosynthesis of proline-rich proteins (Mr 17000-35000) and a Mr-220000 glycoprotein were detectable by solubilization in 10%-trichloroacetic acid extracts from parotid glands 14 days after birth. The enzyme lactose synthase (UDP-galactose: 2-acetamido-2-deoxy-D-glucosamine 4 beta-galactosyltransferase) (EC 2.4.1.22) is also induced 4-7-fold in specific activity compared with control neonatal rats, but again only after 14 days post partum, with isoprenaline treatment. This is in accord with the ability of the parotid gland to respond to beta-receptor stimulation and subsequent increases in intracellular cyclic AMP necessary for induction of protein synthesis [Grand, Chong & Ryan (1975) Am. J. Physiol. 228, 608-612]. Induction of the proline-rich proteins and a Mr-190000 glycoprotein in the soluble fraction from the submandibular gland were not detected until 49 days after birth under identical conditions in the same animal. Cyclic AMP in the submandibular gland undergoes increases on beta-receptor stimulation similar to those achieved in the adult animal, 1 day after birth (Grand et al., 1975). This same differential induction between parotid and submandibular gland was obtained with a range of isoprenaline dosages in adult animals. Trichloroacetic acid-soluble proline-rich proteins were isolated from parotid glands at a dosage of 4.0 mg of isoprenaline/kg body wt., but 7.0 mg/kg was required to induce also biosynthesis of these proteins in the submandibular gland. Gland hypertrophy showed the same differential dosage kinetics, based on gland weight, between the two glands; however, hypertrophy could be accomplished at a lower dosage of isoprenaline than that used to induce proline-rich-protein biosynthesis.     

Effects of saliva from chronically reserpinized rat on Na and K transport in perfused main excretory duct of submandibular gland of normal rat

Reserpine (RES) (0.5 mg/kg body wt, ip) was administered to rats for 7 days. On Day 8 saliva was evoked from these animals by intraperitoneal injection of pilocarpine nitrate (10 mg/kg body wt) and saliva from submandibular and parotid glands was collected separately. These collected salivas were used to perfuse through the main ducts of the submandibular glands of normal rats. After a control period of perfusion of the main duct with bicarbonate saline solution, parotid saliva from RES rats was perfused through the duct followed by regular perfusion. There was inhibition of Na absorption (22%) and K secretion (23%). Moreover, when submandibular saliva from treated rat was perfused through the main duct prior to regular perfusion, there was a decrease in Na absorption (31%) and K secretion (28%). In contrast, perfusion of the main duct with either parotid or submandibular saliva from normal rats caused no significant changes in Na and K transport. The present experiments confirm previous studies that there is some Na-inhibitory factor(s) present in saliva of the chronically RES-treated rat.     

Nervous control of mammalian salivary glands

In the production and flow of saliva, sympathetic and parasympathetic nerves generally cooperate, although variations between the different salivary glands are considerable, particularly in the sympathetic innervation. In the submandibular gland of the dog, sympathetic impulses cause secretion via beta-adrenoceptors, and since sympathetic motor effects are elicited via alpha-adrenoceptors it is possible to study separately motor and secretory effects in this gland. Such experiments indicate that myoepithelial contractions serve to accelerate the salivary flow and to support the secreting acinar cells and prevent back-flow of fluid from the luminal system into the glandular tissues. The contractions are elicited reflexly from the oral mucosa together with secretion. A potentiation interaction between sympathetic and parasympathetic nerves occurs in the formation of the primary saliva. In parotid glands of rabbits and rats such an interaction has been demonstrated in the secretion of amylase.     

Expression and distribution of osteopontin and matrix metalloproteinase (MMP)-3 and -7 in mouse salivary glands

We investigated the expression and distribution of osteopontin in mouse salivary glands. Western blot analysis showed intense positive bands at the predicted molecular mass (about 60 kDa) in mouse parotid and sublingual glands. However, a cross-reacted band around 30 kDa was strongly detected in submandibular glands. Indirect immunofluorescent analysis showed that osteopontin was localized at the luminal (apical) membranes of the acinar cells in parotid and sublingual glands. However, it was not detected in acinar cells of submandibular glands. No expression was found in ductal cells of any glands. We also examined the expression of matrix metalloproteinase (MMP)-3 and -7. In parotid gland, MMP-3 was observed at 57 kDa, indicating a latent form, but MMP-7 was not detected. In contrast, MMP-7 definitely was observed at 28 kDa area in submandibular gland, whereas MMP-3 was not detected. These results suggest that osteopontin localizes at luminal sites of acinar cells and may be associated with saliva secretion in mouse salivary gland. It is also suggested that osteopontin may be cleaved by MMP-7 in mouse submandibular gland.     

Lack of hemostatic effects of adult and suckling cat salivary gland heteropolysaccharides on blood coagulation

Like other mammalian salivary glands, the cat submandibular and parotid glands belonging to adult and growing subjects contain heteropolysaccharides with very heterogeneous composition. Such glycoconjugates were this time tested in humans at doses used previously showing anticoagulant properties in rodents and lagomorphs. But surprisingly, no anticoagulant effects could be detected consistently. In fact, neither thromboelastography, nor hemocoagulation screening tests were affected in a statistically significant manner.     

Effects of acute starvation on carbohydrate metabolism in rat salivary glands.

1. Effects of acute starvation on enzymes of carbohydrate metabolism were determined in rat submandibular and parotid glands. 2. Activities of glycolytic enzymes were high in submandibular gland, but those of pentose phosphate pathway and glycogen metabolism were high in parotid gland. 3. Enzyme activities were lowered by acute starvation. Refeeding the rats with solid diet restored the enzyme activities, but with liquid diet, only partial recoveries were found in submandibular gland.     

Influence of streptozotocin-induced diabetes on hexokinase activity of rat salivary glands

The influence of diabetes on the enzyme hexokinase (HK) was examined in the salivary glands of rats. Diabetes was induced by an intraperitoneal injection of streptozotocin (60 mg/Kg body weight) in overnight fasted rats (180-200 g). The animals were killed 48 hours and 30 days after the induction of diabetes and the submandibular and parotid salivary glands extracted for use. Hyperglycemia was evaluated by determining the blood sugar. The area occupied by each intralobular component, acini, ducts, total parenchyma and stroma was measured, and no differences were observed compared with control. In the soluble fraction of the submandibular gland, no difference in the specific activity of HK was observed, between the diabetic and control animals, however, the activity per gland and per g of tissue showed lower values than control. The specific activity of the bound form was reduced in the diabetic gland. The results obtained for the parotid gland were different from the submandibular. The specific activity of both the soluble and bound forms were increased in the diabetic animals. The DEAE-cellulose column chromatography of the soluble and bound forms of the enzyme from both glands showed a first peak appearing during the washing of the column and two other peaks were eluted by the gradient. Thus, three isoenzymes in the submandibular and parotid salivary glands for the control and diabetic rats have been found.     

Effect of parotid submandibular and sublingual saliva on wound healing in rats.

1. The effectiveness of wound licking with parotid, submandibular or sublingual saliva on wound healing was evaluated in selectively sialadenectomized rats. 2. The rate of healing of experimentally induced cutaneous wounds was evaluated macroscopically by photography at 0, 2, 4 and 6 days after surgery. 3. Sialadenectomy of all major glands significantly slowed down wound healing compared to sham-operated controls. 4. Parotid licking had no effect compared to controls; submandibular licking and sublingual licking appeared to be very effective. 5. The results suggest that saliva promotes wound healing in experimentally induced cutaneous wounds by communal licking; this is a result of the submandibular and sublingual saliva and not the parotid saliva.     

Characterization of mouse salivary glands by water content and type

The thermoanalytical analysis was applied to samples of sublingual, submandibular and parotid glands from sexually mature mice of both sexes. Findings indicated that the three salivary glands show a behaviour of water release characteristic for each type of gland. Derivative thermogravimetry curves concerned with the sublingual and parotid glands belonging to male and female subjects exhibited overlapped results. As regards submandibular gland, instead, some differences emerged between subjects of different sex. Water content and types in sublingual, submandibular and parotid glands were discussed and related to the different morphological expression, histochemical reactivity and chemical composition of these organ tissues.     

Modulating effects of prostaglandins on parasympathetic-mediated secretory activities of rat salivary glands

Exogenously administered PGE1 or PGE2, like atropine, markedly decreased both the flow and calcium concentration of parasympathetically evoked rat parotid saliva; PGF2 alpha was less effective. Despite the fact that prostaglandins greatly reduced the Ca concentration of nerve-evoked saliva, they did not change the glandular Ca concentration of either control or parasympathetically stimulated parotid glands. Prostaglandins (20 micrograms/kg, i.a.) decreased the Na or K concentration of nerve-evoked parotid saliva, but at lower doses had no significant effect. PGE1, PGE2, PGF2 alpha or atropine markedly decreased flow rates of similarly evoked rat submandibular saliva. Prostaglandins and atropine, however, decreased the Na concentration and increased the K concentration of parasympathetically evoked submandibular saliva. PGF2 alpha, like atropine, increased the Ca concentration of such saliva. Drug vehicle, ethanol, slightly decreased the flow of both parotid and submandibular saliva but not the ion secretion, Endogenous prostaglandins themselves may not play a role in secretory activities during parasympathetic nerve stimulation of rat salivary glands, since administration of indomethacin, and inhibitor of prostaglandin biosynthesis, prior to or during nerve stimulation did not significantly alter nerve-evoked salivary secretion, The mechanisms by which prostaglandins modulate secretory responses of salivary glands during parasympathetic stimulation are not understood.     

Kallikrein localization in rodent salivary glands and kidney with the immunoglobulin-enzyme bridge technique.

Kallikrein has been localized in rodent kidney and salivary glands by means of an immunoglobulin-enzyme bridge technique. In sections of kidney, anti-kallikrein antibodies bound to the apical region of certain distal tubule segments in the cortex, to reabsorption droplets of proximal convoluted tubules, and to certain duct segments in the papilla. In salivary glands of both male and female rats and mice, and apical rim of most striated duct cells of submandibular, parotid and sublingual glands and granular tubules of submandibular glands exhibited immunoreactivity. Granular intercalated duct cells in female submandibular glands also displayed immunostaining for kallikrein. Phenylephrine administration resulted in loss of immunoreactive granules from the granular convoluted tubule cells of male mouse submandibular gland. This response was paralleled by a biochemically demonstrable decrease in kallikrein-like tosylarginine methyl ester (TAME) esterase activity.     

Immunohistochemical and ultrastructural investigation of acinar cells in submandibular and sublingual glands of rats fed a liquid diet

In atrophic parotid glands induced by liquid diet, acinar cell apoptosis is increased while proliferative activity is reduced. This study aimed to clarify how liquid diet affects submandibular and sublingual glands, including acinar cell apoptosis and proliferation. Seven-week-old male Wistar rats were fed either a liquid (experimental group) or pellet diet (control group) from 3 to 21 days, respectively. Submandibular and sublingual glands were weighed and examined histologically, ultrastructurally, and immunohistochemically using antibodies to cleaved caspase-3 (Casp-3) and 5-bromo-2′-deoxyuridine (BrdU). Weights of submandibular and sublingual gland from the experimental group were not significantly different from controls at any time point. Histological and ultrastructural characteristics of experimental acinar cells in both glands were normal. Acinar cells in control and experimental submandibular glands were positively stained with periodic acid Schiff (PAS) and weakly stained by alcian blue (AB). In control and experimental sublingual glands, mucous acinar cells were PAS-positive and strongly AB-positive. Although Casp-3- and BrdU-positive acinar cells were identified in both glands in the experimental group, their labeling indices were not significantly different from controls. In conclusion, liquid diet in rats does not induce atrophic alterations to acinar cells, including apoptosis and proliferative activity in submandibular and sublingual glands.     

Expression and induction by beta-adrenergic agonists of the cystatin S gene in submandibular glands of developing rats.

Repeated administration of the beta-adrenergic agonist isoprenaline (isoproterenol, IPR), which produces hypertrophic/hyperplastic enlargements of rat submandibular and parotid glands, induces synthesis of a secretory protein shown to be a cysteine proteinase inhibitor, rat cystatin S. In the current study, Northern blot and hybridizations in situ were carried out to establish the developmental and beta-adrenergic regulation of the expression of the cystatin S gene. Cystatin S mRNA was not detected in submandibular glands of 20-day-old fetuses, nor in the glands of newborn or 10-day-old rats. However, steady-state levels of cystatin S mRNA increased between 21 and 28 days, reaching a conspicuously high concentration at 28 days; cystatin S mRNA then declined rapidly to a barely detectable level in glands of 32-day-old rats. IPR administration for 4 days induced high levels of cystatin S mRNA in submandibular glands of developing and adult rats. In both prepubertal and mature animals, induction of cystatin S mRNA in submandibular glands was more pronounced in female than in male animals. Hybridizations in situ revealed cystatin S mRNA only in acinar but not in duct cells of the submandibular gland. Developmentally, expression of the cystatin S gene coincided with acinar cell differentiation. These data suggest a complex neural, hormonal and developmental regulation of salivary cystatin genes.     

Use of Biometric Characteristics of Major Salivary Glands as a Baseline to Develop a Formula for the Quantitative Estimation of Posttraumatic Regeneration of Glandular Tissue

In experiments conducted on 903 rats, we studied the biometric characteristics of the major salivary glands (parotid, submandibular, and sublingual glands) during ontogenesis. We calculated the indices of nondirectional fluctuation asymmetry for the submandibular and sublingual glands and determined correlation coefficients and the coefficients of linear regression between salivary glands, rat body weight, and the weight of the femoral bone (the largest bone in the rat). The strongest correlation was found between the dry weight of the submandibular gland and the rat body weight. Mathematical analysis of the growth of the submandibular gland after sialotomy allowed us to derive a formula for the quantitative estimation of regeneration, taking into account the natural growth of the rat.     

Use of biometric characteristics of major salivary glands as a base line to develop a formula for the quantitative estimation of posttraumatic regeneration of glandular tissue

In experiments conducted on 903 rats, we have studied biometric characteristics of the major salivary glands (parotid, submandibular, and sublingual glands) during ontogenesis. We have calculated the indices of non-directional fluctuation asymmetry for the submandibular and sublingual glands and determined correlation coefficients and coefficients of linear regression between salivary glands, rat body weight, and the weight of the femoral bone (the largest bone in the rat). The strongest correlation was found between the dry weight of the submandibular gland and the rat body weight. Mathematical analysis of the growth of the submandibular gland after sialotomy allowed us to derive a formula for the quantitative estimation of regeneration, taking into account the natural growth of the rat.     

Effect of nitrendipine, a calcium antagonist, on cell volume in rat salivary glands after isoproterenol stimulation.

Four days of isoproterenol injections induced a marked enlargement of the rat parotid and submandibular glands reflected in significant increases in the absolute and relative wet and dry weight of the glands. The enlargement in parotid gland was attributable at least in part to cellular hypertrophy inasmuch as the average volume per cell of acinar cells increased. In contrast, the average volume of acinar cells in the submandibular gland was decreased as compared to that of control. It is likely that hyperplasia in both groups accounts in part for the enlargement. The slow calcium channel is unlikely involved in the isoproterenol-induced stimulation of the gland, inasmuch as the calcium channel antagonist did not modify the enlargement of the parotid or submandibular glands.