ALTERATION BY LEAD ACETATE OF RAT SUBMANDIBULAR GLAND MORPHOLOGY AND ULTRASTRUCTURE

Protection by sildenafil and theophylline of lead acetate-induced oxidative stress in rat submandibular gland and saliva

The role of oxidative stress in lead toxicity has been proposed in many organs, however, no study has been performed in the salivary glands, which are important parts of the gastrointestinal tract with a high implication in health of the whole body. Recently, it has been proposed that increasing the levels of cGMP and cAMP in the cells may protect from the neurotoxicity of lead. The objective of this study was to determine the ability of lead acetate to produce oxidative stress in rat submandibular as the main salivary gland of the body and to study the role of pretreatment by specific phosphodiesterase inhibitors in the prevention of oxidative stress. Lead acetate (100 mg/kg), alone or in combination with theophylline (25 mg/kg) and sildenafil (5 mg/kg), was administered intraperitoneally to rats. After 2 hours and under general anaesthesia, the submandibular gland ducts were cannulated intraorally using microcannula, and pure saliva was collected for 30 min using pilocarpine (8 mg/kg) as a secretagogue. The submandibular glands were then isolated free under surgery. Oxidative stress in the gland and pure saliva were evaluated measuring lipid peroxidation (thiobarbituric acid reactive substances assay), total thiol groups content and total antioxidant capacity (the ferric reducing ability assay). Results showed significant oxidative stress in the gland and secretions as indicated by increased lipid peroxidation, decreased total antioxidant capacity and thiol group levels. The use of cAMP and cGMP phosodiesterase inhibitors, theophylline and sildenafil, prevented leadinduced increased lipid peroxidation and also protected from decreased thiol groups content and total antioxidant power of the gland and secretions. The same trend of effects was observed in gland and saliva. It is concluded that lead toxicity is mediated through oxidative stress in salivary glands, while increasing intracellular cAMP and cGMP levels may prevent lead-induced oxidative stress.

Structural and functional changes by Ciprofloxacin of rat submandibular gland

In the present study, the effects of Ciprofloxacin (Cipro), a fluoroquinolone antibiotic, on rat submandibular gland structure and function were examined in an acute experiment. Cipro was administered intraperitoneally at various doses (20, 40 and 80 mg/kg). Pure submandibular saliva was collected intraorally by micropolyethylene tubes under anaesthesia using a dissecting microscope. After collection of saliva, submandibular glands were removed and weighed. Flow rate, amylase activity, total protein and electrolyte concentrations were measured in saliva. Concentrations of DNA and protein were measured in the gland. All doses of Cipro (20, 40, 80 mg/kg) reduced salivary flow rate. Concentrations of salivary total protein and calcium and gland DNA were reduced by all doses of Cipro. Treatment by Cipro (80 mg/kg) induced an increase in salivary sodium and potassium concentrations. Histopathological examination of glands revealed that Cipro at doses of 40 mg/kg and 80 mg/kg induces morphological changes in the glands including irregular shape of the cerous and mucous bobbles, lack of nucleus in some cells, damage of the cytoplasmic and cell walls and presence of oncocytes in secretory ducts. It is concluded that Cipro inhibits rat submandibular gland functions consistent with structural damages to the gland that might be observed as a side effect in humans. Properties of fluoroquinolones to alter intracellular cAMP and their ability to suppress DNA and protein synthesis of acinar cells might be possible reasons for observed changes.

Protection by nitric oxide of morphine-induced inhibition of rat submandibular gland function

The effects of morphine, l -arginine (nitric oxide precursor) and l -NAME (nitric oxide synthesis inhibitor ) and their concurrent therapy on rat submandibular secretory function were studied. Pure submandibular saliva was collected intraorally by micro polyethylene cannula from anaesthetized rats using pilocarpine as secretagogue. Single intraperitoneal injection of morphine (6 mg kg(-1)) to rats induced significant (P< 0.01) inhibition of salivary flow rate (28%), total protein (12%) and calcium concentrations (27%). Sodium output was increased (23%, P< 0.01). Single intraperitoneal administration of l -arginine (100 mg kg(-1)) and l -NAME (10 mg kg(-1)) affected salivary gland function. Saliva flow rate was reduced by l -NAME (23%, P< 0.01). The total protein concentration of saliva was increased by l -arginine (21%, P< 0.05) and decreased by l -NAME (19%, P< 0.01). Calcium concentration of saliva was increased by l -arginine (25%, P< 0.01) and reduced by l -NAME (21%, P< 0.01). In combination treatment, l -arginine prevented (P< 0.01) morphine-induced reduction of flow rate while l -NAME potentiated it (P< 0.01). The secretion of total protein and calcium were influenced in a similar trend by concurrent therapy. l -NAME potentiated morphine-induced decrease of total protein and calcium concentrations (P< 0.01) while l -arginine restored (P< 0.01) them to levels close to control and morphine groups respectively. It is concluded that morphine inhibits salivary gland function and nitric oxide (NO) plays a positive role in this system. Also it is confirmed that morphine inhibitory effects on submandibular function are somewhat restored by l -arginine and expanded by l -NAME. The modulatory effect of the l -arginine/NO system on salivary gland function is suggested.

Inhibition of rat parotid and submandibular gland functions by ofloxacin, a fluoroquinolone antibiotic

While fluoroquinolones are widely used in the treatment of various infectious disease, not enough attention has been paid to their adverse effects on salivary glands functions. In the present study, the effects of ofloxacin, a fluoroquinolone antibiotic, on rat parotid and submandibular gland functions, were examined in an acute experiment. Ofloxacin (OFLX) was administered intraperitoneally at various doses (20, 40, and 80 mg/kg). Pure parotid and submandibular saliva were collected intraorally by microployethylene tubes under anaesthesia using a dissecting microscope. Flow rate, amylase activity, total protein, and calcium concentrations were reduced by all doses of OFLX (20, 40, 80 mg/kg, P < 0.01) in parotid saliva. In parotid saliva, sodium and potassium were increased by doses of 20 and 40 mg/kg (P < 0.01) and 20, 40, 80 mg/kg (P < 0.01) respectively. In submandibular saliva, flow rate, total protein and calcium concentrations were significantly reduced by all doses (20, 40, 80 mg/kg, P < 0.01). Sodium and potassium concentrations were also increased by a dose of 80 mg/kg, (P < 0.05) in submandibular saliva. It is concluded that ofloxacin inhibits rat salivary gland functions, which might be observed as a side-effect in humans. Properties of fluoroquinolones to alter intracellular cAMP and calcium levels and their ability to suppress DNA, RNA and protein synthesis of acinar cells might be possible reasons for the observed changes.

Protection by selenium of lead-acetate-induced alterations on rat submandibular gland function

Pure submandibular saliva was collected intraorally by micro polyethylene cannulation of anaesthetized rats using pilocarpine as a secretagogue. Twenty-four days treatment with lead acetate 0.05% in drinking water altered salivary function. Except for flow rate that was (P<0.01) increased by lead acetate, the reminder of parameters, concentrations of total protein and calcium and the activity of N-acetyl-beta-D-glucosaminidase (NAG) in submandibular secretions were decreased significantly (P<0.01) by lead acetate. Selenium (2.5 mg l(-1)) in drinking water for 24 days did not induce any significant change in saliva secretory function. Pretreatment by selenium, prevented the lead acetate-induced decrease of NAG activity and concentrations of calcium and protein (P<0.01). The increased flow rate by lead acetate was also affected by selenium pretreatment and reached the level of control. It is concluded that selenium can protect rat submandibular gland function from lead-acetate-induced adverse effects. Properties of selenium as an antioxidant, free radical scavenger and maintenance of cell membrane integrity may be possible mechanisms of its protective effects.

Alteration by cadmium of rat submandibular gland secretory function and the role of the l-arginine/nitric oxide pathway

The effects of cadmium, l-arginine (nitric oxide precursor) and N(omega)-nitro-l-arginine methyl ester (l -NAME) as a nitric oxide synthesis inhibitor and cotreatment of them on rat submandibular secretory function were studied. Pure submandibular saliva was collected intraorally by micro polyethylene cannula from anaesthetized rats using pilocarpine as secretagogue. Fourteen days treatment with 10 mg l(-1)cadmium as cadmium chloride in drinking water caused significant alterations on salivary function. Salivary flow rate, total protein concentration and amylase activity of saliva were decreased while secretion of calcium was increased by cadmium. Two weeks treatment of rats with l -arginine (2.25%) in drinking water caused an increase in submandibular gland weight. Flow rate was reduced by l-NAME. The total protein concentration of saliva was increased by l-arginine while decreased by l-NAME. Calcium concentration of saliva was reduced by l-arginine and increased by l-NAME. Cotreatment of cadmium with l-arginine prevented cadmium-induced reduction of flow rate while l-NAME cotreatment potentiated cadmium-induced reduction of flow rate. l-arginine showed a preventive effect on cadmium-induced decrease of protein concentration and reached control levels. l-arginine potentiated cadmium-induced increase of saliva calcium concentration. It is confirmed that nitric oxide (NO) has a role in salivary gland function. It is also concluded that cadmium inhibitory effects on salivary gland function are modulated by the NO system as it is observed that the cadmium inhibitory effect on submandibular gland function is diminished by l-arginine and extended by l-NAME. Considering the properties of cadmium substitution for calcium in many intracellular events, different types of alterations can be discussed.