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The aim of this study was to evaluate the effect of laser irradiation (LI) on enzymatic activities of amylase, catalase and peroxidase in the parotid glands (PG) of diabetic and non-diabetic rats. Ninety-six female rats were divided into eight groups: D0; D5; D10; D20 and C0; C5; C10; C20, respectively. Diabetes was induced by administration of streptozotocin and confirmed later by the glycemia results. Twenty-nine (29) days after the induction, the PGs of groups D5 and C5; D10 and C10; D20 and C20, were irradiated with 5 J/cm(2), 10 J/cm(2) and 20 J/cm(2) of laser diode (660 nm/100 mW) respectively. On the following day, the rats were euthanized and the enzymatic activity in the PGs was measured. Diabetic rats that had not been irradiated (group D0) showed higher catalase activity (P < 0.05) than those in group C0 (0.14 +/- 0.02 U/mg protein and 0.10 +/- 0.03 U/mg protein, respectively). However, laser irradiation of 5 J/cm(2) and 20 J/cm(2) decreased the catalase activity of the diabetic groups (D5 and D20) to non-diabetic values (P > 0.05). Based on the results of this study, LI decreased catalase activity in the PGs of diabetic rats.

Many studies suggest that fluoride exposure can inhibit the activity of various enzymes and can generate free radicals, which interfere with antioxidant defence mechanisms in living systems. To further the understanding of this issue, this present study examined the effects of low-dose fluoride treatment on the activity of enzymatic antioxidant superoxide dismutase (SOD) and catalase (CAT), as well as the levels of lipid peroxidation (LPO) in the parotid (PA) and submandibular (SM) salivary glands of rats. Rats were injected with a single dose of sodium fluoride (NaF) (15 mg F−/kg b.w.) then euthanized at various time intervals up to 24 hours (h) following exposure. NaF exposure did not cause significant differences in SOD or CAT activity or LPO levels in PA glands compared to control. Conversely, SM glands presented increased SOD activity after 3 h and decreased SOD activity after 1, 12, and 24 h, while LPO was increased after 6, 12, and 24 h of the NaF injection. There were no significant differences in the CAT activity in the groups studied. Our results demonstrated that NaF intoxication caused oxidative stress in salivary glands few hours after administration. These changes were more pronounced in SM than in PA gland.

Background: Saliva is supersaturated with respect to calcium and phosphate ions. Salivary ions may well play a role in the subsequent adsorption of proteins and consequently in the formation of the acquired enamel pellicle. Among several biological functions, the enamel pellicle forms a selectively permeable barrier that regulates demineralization processes. Aim: The aim of this study was to evaluate the importance of salivary proteins when adsorbed on enamel surface and the resultant protective effect against demineralization without the presence of salivary ions. Methods: Enamel surfaces were coated with whole saliva, parotid saliva, dialyzed whole saliva or dialyzed parotid saliva (molecular weight cutoff 1 kDa). Adsorption was allowed to proceed for a period of 2 h. Enamel specimens were then washed with deionized water and immersed into a demineralization solution of pH 4.5 for 12 days. This solution was used to measure the amount of calcium and phosphate released from enamel specimens after the demineralization period. Results: All coated specimen groups showed a significantly higher protection than those not coated with any type of saliva. In addition, undialyzed saliva (whole saliva and parotid saliva) was more effective in protecting the enamel against demineralization than dialyzed saliva. Conclusion: The present investigation indicates that the ionic composition of saliva can amplify the demineralization protection effect by reducing acid-induced enamel demineralization. Moreover, a protective effect of salivary proteins without presence of ions was demonstrated in this study.

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Fluoride (F) is a toxicological axiom. Many reports have proposed that in varying concentrations, F induces increased reactive oxygen species generation, enhanced lipid peroxidation and impairs the antioxidant enzyme defence system in blood and tissues of experimental animals causing several biochemical alterations. Although the most pronounced effects of F intake are manifested in bones and teeth, soft tissues are also affected. Due to the paucity of reports investigating the short-and long-term effects of varied doses of F on soft tissues, especially salivary glands, this study aimed to evaluate the acute and long-term effects of sodium fluoride (NaF) exposure on antioxidant enzyme defence system and lipid peroxidation in the submandibular (SM) and parotid (PA) salivary glands of rats. For the acute investigation, the experimental groups of rats were injected intraperitoneally with NaF solution (15 mg F-/kg b.w.), while control groups were administered the same volume of sodium chloride solution (0,9%). The animals were euthanized in groups 1, 3, 6, 12 and 24 hours after injection. To evaluate long-term exposure effects, experimental groups of rats were administered 100 pmm Fin their drinking water for 30, 60 and 90 days. The control groups were provided with untreated tap water over the same periods. In all groups, after euthanization the SM and PA glands of each rat were extracted and analyzed for superoxide dismutase (SOD) and catalase (CAT) activities, malondialdehyde (MDA), protein and blood glycemia content. For both acute and long-term experiments, the experimental groups demonstrated higher levels of glycemia, altered levels of SOD and CAT in both glands, and increased levels of MDA in blood and salivary tissues of both glands. There were no differences in protein content for the acute experiment, but in the long-term experiment, increased protein levels were observed after 90 days in the SM gland and decreased protein levels were observed in the PA gland after 30 and 60 days. These results suggest that F impaired the antioxidant defence system and enhanced the levels of MDA in blood and SM and PA salivary glands of rats.