Effects of glucocorticoids upon the glycosaminoglycans in salivary glands in the rat

The glycosaminoglycans of the salivary glands were studied in male rats after adrenalectomy and after the daily administration of either 100 or 300 μg of cortisol acetate to adrenalectomized rats during one month. Total uronic acid concentration was determined in the salivary glands. Chromatographic separation of the uronic acid fractions was performed on cellulose microcolumns. Adrenalectomy decreased the uronic acid concentration in the submaxillary and retrolingual glands, while the administration of cortisol acetate increased its concentration in these glands. No changes were detected in the uronic acid concentration in the parotid glands. Adrenalectomy affected the glycoprotein, hyaluronic acid and dermatan sulphate fractions, while cortisol acetate affected the hyaluronic acid, chondroitin-4-sulphate and chondroitin-6-sulphate fractions.     

Effect of feeding different levels of corn oil on the composition of submandibular salivary gland fatty acids in rats

Male, weanling rats were fed synthetic diets containing 0, 3, 10 and 20 per cent corn oil. Rats were killed after 3 weeks, their plasma and submandibular salivary glands were extracted for lipids, and the fatty acid composition was determined. There were significant changes in the fatty acid composition of both plasma and submandibular salivary glands as a result of feeding different levels of corn oil in the diet. The proportions of monoenoic fatty acids (16:1, 18:1) decreased whereas those of linoleic acid increased as the level of corn oil was increased from 0 to 20 per cent. Arachidonic acid level was the lowest in the fat-free group as compared with the other groups. Plasma and submandibular salivary gland lipids of rats fed 0 per cent corn oil in their diet contained another fatty acid which appears to be eicosadicnoic fatty acid. The changes in submandibular salivary gland fatty acids were correlated with the changes in plasma fatty acids. Fractions of neutral lipids and phospholipids which were isolated from the submandibular salivary glands showed changes in their fatty acid composition similar to those observed in the total lipid extract.     

Effects of oestrogens upon the sialic acid in the submaxillary and sublingual glands in the rat

The effect of castration and of the daily administration of 1 or 10 μg of oestradiol benzoate during 1 month to spayed female rats upon sialic acid concentration in the submaxillary and sublingual glands and in plasma was studied. The weight and the sialic acid concentration in both glands was not significantly altered by castration. The administration of oestradiol benzoate increased the weight and sialic acid concentration in the submaxillary glands, but it did not affect the weight and decreased the sialic acid concentration of the sublingual glands. The plasma sialic acid concentration was decreased by spaying and increased by the administration of oestradiol benzoate to castrated rats.     

Effect of isoprenaline on salivary gland lipids of rats fed a choline-deficient diet.

Male adult rats were fed choline deficient and a choline-supplemented diet for 3 weeks. Half the rats from each group were injected with isoprenaline (16 mg/kg body weight) and the remainder with saline. After 2 and 8 hours, rats were sacrificed, their submandibular salivary glands were disected out, and extracted for lipids. The fatty acid composition of total lipids and some neutral and phospholipid fractions were determined. Isoprenaline administration resulted in a slightly higher level of oleic acid in SMSG of rats fed choline-deficient but not the control diet. There was an increase in the free fatty acid (FFA) concentrations of the gland after 2 hours of isoprenaline treatment in rats fed the control diet; no such increase was observed in the choline-deficient group. The fatty acid composition of FFA fraction was also slightly changed as a result of isoprenaline treatment, but only in the choline-deficient group. The fatty acid composition of triglyceride (TG), phosphatidyl choline (PC), and phosphatidyl ethanolamine (PE) fractions was not changed.     

Effects of cadmium on the function and structure of the rat salivary glands

The effects of sub-chronic cadmium (Cd) administration on the structure and subsequent secretory responses of the submaxillary and parotid glands to sialagogues were investigated. Female Wistar rats were injected subcutaneously with cadmium chloride (3.0 mg/kg body weight), 4 times a week for 2, 3 or 4 weeks. Functional and histopathological studies were done 3 days after the last injection. Dose-response curves for norepinephrine and methacholine were obtained. After 2 weeks of Cd administration significant changes in the secretory response to these sialogogues were observed. The dose-response curves after pretreatment with Cd for 3 weeks were also shifted to the right, but the response showed recovery when compared with that of 2-week treated animals. Parotid amylase concentration was also diminished by Cd. Treated rats had reduced acinar diameters, and an increase in acinar cell nuclei per field in both the submaxillary and parotid glands. Thus sub-chronic administration of ionized Cd produces morphological and functional changes in rat salivary glands. Moreover, the extent of tubular and acinar damage matches the degree of gland dysfunction as judged by the diminution of secretory responses to sialagogues.     

The effect of alloxan diabetes and insulin in vivo on peroxidase activity in the rat submandibular gland.

Protein content and peroxidase activity were determined in submandibular salivary gland homogenates from control and alloxan-diabetic rats. Fourteen days after alloxan administration, peroxidase activity and protein in the glands of diabetic rats were lower than in control rats. Stimulation of salivary secretion with pilocarpine produced a decrease in the difference between the peroxidase activities in the glands from control and diabetic animals. Insulin treatment of alloxan-diabetic animals produced an increase in submandibular gland peroxidase activity to control levels within 3 hours.     

A quantitative study of the effects of chronic hypoxia on the histological structure of the rat major salivary glands

Ten young adult female Wistar rats were placed in a decompression chamber at a simulated altitude of 5500 m for 28 days, after which they were killed and their salivary glands and thoracic organs were compared with those of eight matched control rats that had been maintained at sea-level atmospheric pressure. The prolonged hypoxic conditions were severe enough to induce structural changes in the heart and lungs of experimental rats, and their parotid and submandibular, but not sublingual, glands showed severe hyperaemic responses. However, no parenchymal changes occurred in any of the major salivary glands. The mean proportional volume of vascular tissue was increased by 57% in the parotid and 30% in the submandibular glands, and the mean intralobular capillary densities were also increased, by 29 and 18% respectively, in these two glands. The effectiveness of these vascular responses in protecting the salivary parenchymal elements against hypoxic degeneration probably reflects the high reserve potential normally present in salivary blood flow.     

Altered glycogen metabolism in the submandibular and parotid salivary glands of rats with streptozotocin-induced diabetes

Experimental animal models of diabetes induced either by alloxan or streptozotocin have been used to study aspects of the pathophysiology of this disease. The purpose of this study was to examine the metabolism of glycogen in the submandibular and parotid salivary glands of diabetic rats. Diabetes was induced by an intraperitoneal injection of streptozotocin. Eight weeks after the induction of diabetes, the animals were sacrificed and the submandibular and parotid salivary glands were removed. The glands were analyzed for glycogen concentration, and activities of glycogen synthase and phosphorylase. Although the diabetic rats consumed more food than controls, they had a lower body weight eight weeks after diabetes induction. Glycogen concentration in the submandibular and parotid glands increased by about 27% and 130%, respectively. Glycogen phosphorylase a in the submandibular gland of diabetic rats showed a reduction of between 75% and 68% compared with controls. In parotid glands, phosphorylase a was reduced by between 84% and 79% compared with controls. The increase in the activity of glycogen synthase a (active) varied from 64% to 130% for the submandibular glands and from 75% to 110% for the parotid compared with controls. These results suggest that the diabetic state influences glycogen metabolism in the submandibular and parotid salivary glands of rats.     

Activity, distribution and regulation of phosphofructokinase in salivary gland of rats with streptozotocin-induced diabetes

Although the influence of diabetes on salivary glands is well studied, it still presents conflicting results. In this work, the regulation of the phosphofructokinase-1 enzyme (PFK-1) was studied utilizing the salivary glands of rats. Diabetes was induced by a single intraperitoneal injection of streptozotocin (60 mg/Kg of body weight) in rats (180-200 g). The animals were killed 30 days after the induction of diabetes and the submandibular and parotid salivary glands were used. Hyperglycemia was evaluated by blood sugar determination. The distribution of PFK-1 between the soluble and cytoskeleton fractions, the phosphate content of PFK-1, the content of fructose-2,6-bisphosphate and the activity of the PFK-2 enzyme were determined. The calculated relative glandular weight showed a higher value for the parotid gland in comparison with the control, but not for the submandibular gland. The activity of PFK-1 expressed per gland showed no variation between diabetic and control animals. However, considering the specific activity, the soluble enzyme presented a value 50% higher than that of the control and the cytoskeleton bound form increased by 84% compared to the control. For the parotid gland, no difference in the specific activity between diabetic and control animals was observed. On the other hand, the activity per gland of the soluble enzyme increased in the diabetic animals. The phosphate content of PFK-1 increased in the submandibular and parotid glands of diabetic rats. Both the content of fructose-2,6-bisphosphate and the active form of PFK-2 were reduced in the diabetic glands. In conclusion, the increase in the activity of PFK-1 observed in the salivary glands of rats with streptozotocin-induced diabetes does not seem to be due to its modulator fructose-2,6-bisphosphate.     

Effect on peroxidase activity and specific binding of the hormone 17 beta-oestradiol and rat salivary glands

The effect was studied on immature and adult female rats. Oestradiol, given either once (10 micrograms) or three times (3 X 10 micrograms) subcutaneously significantly retarded the total weight gain of immature rats whereas, at the same time, the weight of the uteri increased several fold. The weights of neither salivary nor lacrimal glands were dependent on oestradiol. The activity of the peroxidase enzyme, a marker of oestrogen-responsive tissues, increased significantly in the rat uteri but had no effect on lacrimal peroxidase. The levels of rat salivary peroxidase increased during oestradiol administration with considerable differences between various glands. The increase in peroxidase activities could not be explained by changes in the total protein content but seemed to be specific for this enzyme. Experiments using [3H]-oestradiol indicated specific binding to uterus, parotid and submandibular glands. It is concluded that rat salivary glands are oestrogen-responsive.     

Lipid analysis of the major salivary glands in streptozotocin-diabetic rats and the effects of insulin treatment.

Two separate sets of experiments were performed on female Wistar rats made diabetic with streptozotocin: (1) a time-course study where groups of three animals were removed at weekly intervals, up to 4 weeks after induction of diabetes, with an age-matched group of control (normal) animals kept for 4 weeks; (2) six further animals were made diabetic and kept for 7 weeks; three of these were given insulin in the final week. At the required time the animals were anaesthetized and the salivary glands removed and preserved by fixation or freezing. The frozen tissues were later homogenized and the protein and lipid content analysed. Histologically, intracellular lipid droplets had accumulated in the majority of the diabetic salivary glands. In the time-course experiment, the visible amount of intracellular lipid reached a maximum after 2 weeks and then decreased, with a concomitant disappearance of interstitial lipid. The increased lipid content was not attributable to any one class. The fatty acid profiles of the glands showed an increase in the percentages of C18:0 (stearic acid) and C18:2w6 (linoleic acid) and a decrease in the percentages of C18:1w9 (oleic acid) and C20:4w6 (arachidonic acid). After 1 week of insulin treatment the lipid content and the fatty acid profiles returned to normal. Thus the effect of insulin on salivary gland lipid metabolism is rapid both in its occurrence and reversibility. The effects seen in the diabetic rats are considered to be due to a lack of insulin and not to the presence of streptozotocin.     

Effect of injection of different concentrations of lidocaine into the rats salivary glands

The effects of different doses of lidocaine with or without epinephrine on the rat's salivary glands were studied in this report. 60 adult male albino rats were divided into 4 experimental groups and one control group' 1 st group, the salivary glands were injected with 0.1 ml of 2% lidocaine Hcl. 2 nd group, the salivary glands were injected with 0.5 ml of 2% lidocaine Hcl. 3 rd group, the salivary glands were injected with 0.1 ml of lidocaine Hcl + 1/200,000 epinephrine, while the 4 th group, the glands were injected with 0.1 ml of lidocaine Hcl + 1/80.000 epinephrine. The control group was injected with 0.1 ml of physiologic asline. Each group of animals was subdivided into 3 subgroups A, B, and C according to the sacrifice periods which were 24, 48 and 72 hours respectively. After sacrification the submandibular salivary glands were removed and prepared for histological and histochemical studies. Our results revealed that, lidocaine in relevant doses with or without epinephrine produced reversible damage to the terminal portions of salivary glands. Large doses of lidocaine produced massive damage and delayed healing. Epinephrine concentration of 1/200.000 is recomended by the authors as higher concentration produced sever and extensive damage.     

The effect of local injection of botulinum toxin A on the parotid gland of the rat: an immunohistochemical and morphometric study.

PURPOSE: In this investigation, the effect of a local injection of botulinum toxin A on the concentration of acetylcholinesterase in the parotid gland of the rat was examined. MATERIALS AND METHODS: After local injection into the parotid glands of female Wistar rats, the treated glands were excised, and immunohistochemical staining for acetylcholinesterase was performed. To discover possible changes in cell morphology after local application of botulinum toxin A, morphometric measurements also were performed on the excised parotid glands. RESULTS: In contrast to the untreated, physiologic saline-injected, glands, there was a decrease in the concentration of acetylcholinesterase in the glands treated with botulinum toxin. No persistent changes in the number of acinar cells could be observed. Conclusions: Because the cholinergic pathway of the autonomic nervous system has great importance in the secretion of fluid from the salivary glands, blocking this pathway and local application of botulinum toxin offers a possible therapeutic option for the treatment of hypersalivation in various otolaryngologic and neurologic diseases.     

Secretion from minor salivary glands following ablation of the major salivary glands in rats

Since minor salivary glands are tiny and dispersed, ductal cannulation cannot be used when studying their function. The present study was devised to develop a method of measuring minor salivary gland function by excision of the major glands. Female rats (230–280 g) were anaesthetized with sodium pentobarbital. Ablation of the submandibular, sublingual and parotid glands was performed through a sagittal neck incision. Sham-operated rats served as controls. Groups of sialadenectomized animals were investigated immediately and after 1 week, 2 weeks and 3 months. To study secretory function, the mouth was rinsed with 250 μl water in every 5 min and protein and amylase concentrations were measured. After an initial 50 min of basal secretion pilocarpine (1 mg/kg, i.p.) was given. Bilateral ablation of both submandibular, sublingual and parotid glands led to a moderate loss of body weight and a considerable increase in water intake. No other obvious abnormality was observed for periods up to 90 days following surgery. We deduce that the minor glands secrete approximately 14% of protein and 1% of amylase in whole saliva. Secretion is maintained even after 90 days following removal of the major glands. Surgical removal of the major salivary glands allows the secretory function of the minor glands in rats to be studied in vivo.     

Lipid droplet accumulation and lipoprotein lipase activity in the rat salivary gland during the perinatal period

The submandibular and sublingual glands of foetal and newborn rats aged 21 days in utero to 7 days after birth were examined morphologically and biochemically. Lipid droplets tended to be localized in secretory cells, especially in their basal cytoplasm. The degree of droplet accumulation varied with the age of the rat. No droplets were observed before and immediately after birth. The number of accumulated droplets peaked 24–48 h after birth, then gradually decreased and reached normal levels by 5 days. In the salivary glands of fasted newborn rats, no lipid droplets were observed throughout the experiment. The amount of triacylglycerol reached its maximum level 1 day after birth; it then decreased gradually until 5 days and after that did not change. The amount of cholesterol did not change during postnatal development. Lipase activity attained its maximum level in the salivary glands immediately after birth and then decreased rapidly. It was higher in the glands of fasted than fed 1-day-old rats. Antiserum) against lipoprotein lipase inhibited the salivary gland lipase activity in a dose-dependent manner, with 5 μl of antiserum producing 60–70% inhibition. Nondashimmune serum had little effect. It was concluded that (1) accumulated lipid in the secretory cell cytoplasm of the salivary glands originates from ingested milk; (2) the principal component of accumulated lipid droplets is triacylglycerol; (3) 60–70% of the total lipase activity represents lipoprotein lipase; (4) an increase of lipoprotein lipase activity is recognizable before the accumulation of triacylglycerol.     

Rad50在放射后大鼠涎腺中的表达

目的:检测Rad50在放射后大鼠涎腺组织中的表达水平。方法:选用60只Wistar大白鼠,随机分成6组,每组10只。分为对照组(未照射)、3 Gy组、6 Gy组、9 Gy组、12 Gy组、15 Gy组。放射组大白鼠用60Co一次性照射后2 h内处死,立即取出其腮腺、下颌下腺组织备用。用电镜观察放射后各组涎腺组织超微结构的变化,用反转录聚合酶链反应(RT-PCR)检测Rad50基因表达水平的变化,用免疫组织化学法观察其蛋白表达水平的变化。结果:各放射组涎腺组织中Rad50的表达均高于对照组(P<0.05),但不同放射剂量的各放射组之间Rad50的表达无明显差异(P>0.05)。透射电镜下可见大鼠腮腺、下颌下腺细胞超微结构随着放射剂量的增加,发生较明显改变。结论:放射可引起涎腺组织Rad50表达水平增高,但其表达水平并未随放射剂量的增加而增高,提示Rad50在涎腺放射损伤修复中的表达水平有限,这可能是涎腺放射敏感性机制之一。     

Metabolism of carbohydrate in the major salivary glands of rats.

Oxygen consumption, glucose uptake and lactic acid formation in the presence of glucose as substrate were examined in slices of the major salivary glands from rats starved overnight. Gluconeogenesis was also examined.The presence of glucose in incubation medium increased oxygen consumption of the three salivary glands. The amounts of lactic acid formed during incubation for 2 hr was, in descending order: submandibular, sublingual, parotid. Submandibular and sublingual glands consumed more glucose than parotid. Part of the glucose consumed was used for glycogen synthesis. The use of [1-¹⁴C]-lactate for synthesis of glycogen was negligible. The specific activity of fructose 1,6-diphosphatase was very small and did not alter with starvation.     

A pilot study on the effect of radiation on calmodulin in rat submandibular salivary glands.

Xerostomia and loss of salivary gland secretion is one of the most common complications of the radiation treatment of head-and-neck malignancies. The secretory mechanism in the salivary glands can be modulated by the concentration of intracellular Ca2+. Calmodulin is a calcium-binding protein that is widely distributed in nature and is involved in regulating intracellular calcium. In this study the effect of radiation on the concentration of calmodulin in rat salivary glands was investigated. Fourteen rats were divided into three groups: R1 (n = 4) and R2 (n = 5) received a single dose of 15 Gy and group C (n = 5) received no radiation. R1 and R2 animals were killed at weeks 2 and 10 post-irradiation, respectively. The submandibular glands were removed, homogenized and their total calmodulin was determined. The mean calmodulin concentrations were 6.4+/-1.1 microg/gland for controls, 14.1+/-3.7 microg/gland for R1 and 68.2+/-14.4 microg/gland for R2. Kruskal-Wallis ANOVA revealed a significant increase in the concentration of calmodulin following irradiation (p = 0.003). The relationship between this increase and the loss of salivary gland function is not yet clear.     

Morphological and biochemical changes in the rat parotid gland after compensatory and isoproterenol-induced enlargement

Enlargement of parotid glands can be induced in rats by treatment with isoproterenol (ISP) or by removal of the submandibular and sublingual glands. In this study, morphological changes in the enlarged parotid glands and qualitative changes in secreted proteins were examined in rats that had been treated with ISP for 10 days or that had been partially sialoadenectomized by removal of the submandibular/sublingual glands 2 weeks prior to killing. After ISP treatment or salivary gland ablation, secretory cells were enlarged and contained enlarged secretory granules that stained differently from granules in normal glands. Isoproterenol treatment induced the greatest enlargement of cells and granules. Even though gland structure was altered in both experimental groups, electrophoresis of saliva showed that submandibular/sublingual gland ablation did not lead to significant qualitative changes in secreted proteins, while ISP treatment induced major changes in the pattern of secreted protein. The results suggest that compensatory enlargement of the parotid glands and changes after ISP treatment are induced by stimulation of different regulatory pathways.     

The effect of X-ray irradiation on the function and saliva composition of rat parotid and submandibular/ sublingual glands

Radiation therapy to the head and neck area frequently causes severe salivary gland dysfunction and xerostomia. Morphological studies of irradiated salivary glands have suggested that the submandibular/sublingual gland may be less radiosensitive than the parotid gland. The purpose of this study was to evaluate the effect of radiation on major salivary gland functions in rats with radiation-induced xerostomia. The effect of salivary gland irradiation on salivary function was examined in specific pathogen-free Sprague-Dawley rats. The animals were irradiated with a single exposure of either 22 Gy or 32 Gy. Stimulated saliva excretion time was measured for the parotid and submandibular/ sublingual glands, and the total protein in saliva was analysed. Our results showed that the saliva flow rate and protein concentration of parotid saliva were significantly reduced in the 32 Gy-irradiated rats.