Calcium levels in rat submandibular gland and saliva after sympathetic nerve stimulation in the presence of alpha, beta 1 and beta 2-adrenergic antagonists

Alterations in salivary biochemical composition and redox state disruption induced by the anticonvulsant valproic acid in male rat salivary glands

OBJECTIVE

To investigate the effects of the anticonvulsant valproic acid (VPA) on salivary glands in male rat using biochemical, functional, histomorphometric, and redox state parameters.

MATERIALS AND METHODS

Twenty-four male Wistar rats were randomly distributed into three groups (n = 8 per group): Control (0.9% saline solution), VPA100 (100 mg/kg), and VPA400 (400 mg/kg). After 21 consecutive days of treatment with by intragastric gavage. Pilocarpine-induced saliva was collected to determine salivary flow rate, pH, buffering capacity, and biochemical composition. Analyses of histomorphometric parameters and redox balance markers were performed on the parotid and submandibular glands.

RESULTS

Salivary flow rate, pH, buffering capacity, total protein, potassium, sodium, and chloride were similar between groups. However, phosphate and calcium were reduced in VPA400, while amylase was increased in both VPA100 and VPA400. We did not detect significant differences in the areas of acini, ducts, and connective tissue in the salivary glands between the groups. There were no significant changes in the redox status of the submandibular glands. In turn, in the parotid glands we detected reduced total oxidizing capacity and lipid peroxidation, measured as thiobarbituric acid reactive substances (TBARs) and higher uric acid concentration in both the VPA100 and VPA400 groups, and increased superoxide dismutase (SOD) in the VPA400 group.

CONCLUSION

Chronic treatment with VPA modified the salivary biochemical composition and caused disruption in the redox state of the parotid gland in rats.

Effects on salivary flow rate and composition of withdrawal of and re-exposure to the beta 1-selective antagonist metoprolol in a hypertensive patient population

Secretion rates and composition of unstimulated and chewing-stimulated whole saliva and 3% citric acid stimulated parotid and submandibular-sublingual secretions were studied in 12 hypertensive patients during withdrawal of and re-exposure to antihypertensive pharmacotherapy. All the patients' blood pressures were well controlled by monotherapy with metoprolol, a beta 1-selective adrenoceptor antagonist. Blood pressure measurements and saliva sampling were performed at about 9:30 a.m., 2 h after intake of breakfast, on days 0 (medicated baseline), 7, 14, 28 (nonmedicated experimental values and nonmedicated baseline) and 35 (medicated experimental values). A significant increase in unstimulated whole saliva secretion rate was observed when metoprolol was withdrawn and a corresponding decrease when the drug was reintroduced. A positive correlation was found between diastolic blood pressure levels and chewing-stimulated whole saliva secretion rates. In unstimulated whole saliva and 3% citric acid stimulated submandibular-sublingual secretion, the output of total protein, amylase, potassium, calcium and phosphate was significantly increased during the withdrawal period and decreased when metoprolol was reintroduced. For chewing-stimulated whole saliva, the corresponding changes were restricted to output of total protein and amylase, while for citric acid stimulated parotid secretion, no changes in salivary composition were observed. Finally, in all secretions one or both of the ratios hexosamine/total protein and sialic acid/total protein were affected, indicating a possible effect of beta-adrenoceptor antagonists on salivary protein synthesis.

Effects of the beta-adrenoceptor antagonists atenolol and propranolol on human parotid and submandibular-sublingual salivary secretion

The aim of the study was to evaluate the effects of a beta 1-selective (atenolol 50 mg q.d.) and a non-selective (propranolol 80 mg b.i.d.) beta-adrenoceptor antagonists on human stimulated parotid and submandibular-sublingual (SM-SL) gland secretion. A randomized double-blind, placebo-controlled cross-over ("Latin square") design was used in 19 healthy male volunteers. Stimulated parotid and SM-SL saliva were sampled immediately before and 7 days after the start of each treatment period. Stimulation of salivary secretion was achieved by use of a 3% citric acid solution. Plasma concentrations of propranolol and atenolol were determined from blood samples. The salivary secretion of both glands was assessed for flow rate, amylase, lysozyme, and salivary peroxidase activity and for concentrations of total protein, hexosamine, sialic acid, Ca2+, Cl-, K+, Mg2+, Na+, and PO4(3-). In both parotid and SM-SL secretions, the total protein and phosphate concentrations and amylase activity were significantly decreased during the two active treatment periods. In SM-SL gland secretion, there were significant changes in potassium and calcium concentrations during active treatment as compared with baseline, with potassium showing a decreased and calcium an increased concentration. During atenolol treatment, salivary peroxidase activity decreased significantly in SM-SL secretion. In parotid secretion, the hexosamine/total protein ratio decreased and the sialic acid/hexosamine ratio increased during atenolol treatment, which may indicate an effect on protein synthesis. No significant effects on salivary secretion rates were disclosed.

Histochemical and biochemical determination of calcium in salivary glands of cat

Although feline salivary glands have been used in investigations on secretion and microlithiasis and both processes involved calcium, nothing is known about its distribution in these glands. Therefore we have demonstrated the presence of calcium by a histochemical technique using glyoxal bis(2-hydroxyanil) and a biochemical technique using dry ashing. The histochemical technique stained serous acinar cells weakly and rarely found mucous acinar cells strongly in the parotid gland, mucous acinar cells moderately to strongly and serous acinar cells weakly in the sublingual gland, and central and demilunar acinar cells moderately to strongly in the submandibular gland. The biochemical technique revealed less calcium in the parotid than in the submandibular and sublingual glands. Both techniques revealed a decrease of calcium in submandibular and sublingual glands following parasympathetic stimulation. The histochemical distribution of calcium, which corresponds to that of acinar secretory glycoprotein, and the loss of calcium following parasympathetic stimulation, which causes release of secretory granules, indicate the presence of calcium in secretory granules. The concentration of calcium in the different types of acinar cell corresponds to the acidity of the secretory glycoprotein and suggests that calcium is present as a cationic shield to allow the condensation of polyionic glycoprotein in secretory granules.

Effects of the beta-adrenoceptor antagonists atenolol and propranolol on human whole saliva flow rate and composition

The effects of beta-adrenoceptor antagonists on salivary secretion have been extensively studied in animals but not in man. The aim here was to compare salivary flow rate and composition in man during 1 week of treatment with a non-selective (propranolol 80 mg b.i.d.) and a beta 1-selective (atenolol 50 mg o.d.) antagonist with that of placebo. The randomized, double-blind, cross-over ("Latin square") design was used and 42 healthy male volunteers were recruited to the study. The treatment periods were separated by a wash-out period of 2 weeks. Whole saliva was sampled on day 0 (before) and on day 7 during each treatment. The plasma concentration of propranolol and atenolol was determined from blood samples obtained on day 7. Resting saliva was assessed for flow rate, amylase activity and concentration of total protein, hexosamine and sialic acid. Stimulated saliva was assessed for flow rate, pH, buffer pH, amylase activity and concentration of total protein, Ca2+, Mg2+, Na+, K+, Cl- and PO4(2-). In resting as well as stimulated whole saliva both the total protein concentration and the amylase activity were significantly decreased during the active treatment periods (p less than 0.05-p less than 0.001). At lunchtime during atenolol treatment the hexosamine/total protein and the sialic acid/total protein ratios were significantly increased (p less than 0.05-p less than 0.01), suggesting a possible effect on protein synthesis. In addition, the concentrations of Ca2+, PO4(2-), Cl- and Mg2+ were significantly altered during the active treatment periods (p less than 0.05-p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effects of atropine and adrenergic antagonists on the changes in autonomic receptors and cyclic nucleotides of rat parotid and submandibular glands caused by sympathetic nerve stimulation

The changes in cyclic AMP (cAMP) concentration and density of beta-adrenoceptors caused by electrical stimulation of the sympathetic innervation to parotid and submandibular glands of rat did not occur when the alpha- and beta-adrenergic antagonists, phentolamine, and propranolol were administered 20 min prior to initiation of stimulation. They also did not occur when phentolamine, the beta-adrenergic antagonist, was administered alone prior to nerve stimulation, indicating that beta-adrenoceptors mediate these effects. Simultaneous administration of the alpha- and beta-antagonists also prevented the changes in densities of muscarinic receptors and cGMP concentrations usually induced by sympathetic nerve stimulation. Also, the changes in muscarinic receptors and cGMP did not occur when atropine was administered prior to nerve stimulation, nor did they occur with simultaneous administration of atropine, phentolamine + propranolol; with phentolamine alone, or propranolol alone, the effects were blocked to a large extent. Secretion was inhibited completely when both adrenergic antagonists were present during nerve stimulation, but flow rate was unchanged when atropine was present. The changes in both beta-adrenoceptors and muscarinic receptors reflect a desensitization caused by prolonged exposure to neurotransmitters released when the sympathetic nerve is stimulated. The changes are prevented when either atropine or adrenergic antagonists are present during nerve stimulation.

Effects of alpha, beta 1, and beta 2 adrenergic antagonists on the Na and K concentrations of sympathetic-nerve stimulated rat saliva

Selective alpha and beta 1 and beta 2 adrenergic antagonists were used with electrical stimulation of the sympathetic innervation to parotid and submandibular glands of rats in order to delineate the role of the beta 1 and beta 2 adrenoceptors in regulation of salivary flow rate, Na reabsorption and K secretion from these glands. In parotid gland, [Na] of sympathetically evoked saliva in the presence of phentolamine (3 mg/kg, i.p.) was not different from that of nerve-evoked saliva in the presence of phentolamine and butoxamine (3 mg/kg, i.p.), except for the last 20 min of stimulation when [Na] of nerve-elicited saliva was higher. [K] of saliva with sympathetically evoked stimulation was the same in the presence of phentolamine alone as it was or in the presence of phentolamine and butoxamine. Again, there was no difference in salivary flow rate induced by either kind of stimulation, except for the first 10 min of stimulation, during which salivary flow rate of nerve-evoked saliva in the presence of phentolamine was lower than under the other conditions indicated. On the other hand, with submandibular gland, [Na] and [K] of nerve-elicited saliva in the presence of phentolamine were generally higher than levels of sympathetically evoked saliva in the presence of phentolamine and butoxamine. However, salivary flow rate of nerve-evoked saliva in the presence of phentolamine was generally lower than that of sympathetically evoked saliva in the presence of phentolamine and butoxamine.(ABSTRACT TRUNCATED AT 250 WORDS)