On the relation of calcium channel blockers to rat parotid and submandibular glands function in vivo

Assessment of the toxic effects of levetiracetam on biochemical, functional, and redox parameters of salivary glands in male Wistar rats

Levetiracetam (LEV) is an anticonvulsant for epilepsy. The toxic effects of this medication in tissues have been associated with redox state imbalance, which can lead to salivary gland dysfunction. Therefore, the current work investigated the effects of LEV on the biochemical, functional, and redox parameters of the parotid and submandibular glands in rats. For this, male Wistar rats (Rattus norvegicus albinus) were randomly divided into 3 groups (n = 10/group): Control (0.9% saline solution), LEV100 (100 mg/kg), and LEV300 (300 mg/kg). After 21 consecutive days of intragastric gavage treatments, pilocarpine stimulated saliva secretion was collected for salivary biochemical analysis. The extracted salivary glands were utilized for histomorphometry and redox state analyses. Our results showed that LEV300 increased plasma hepatotoxicity markers and reduced salivary amylase activity and the acinar surface area of the parotid gland. Total oxidant capacity and oxidative damage to lipids and proteins were higher in the parotid gland, while total antioxidant capacity and uric acid levels were reduced in the submandibular gland of the LEV100 group compared to Control. On the other hand, total oxidant capacity, oxidative damage to lipids and proteins, total antioxidant capacity, and uric acid levels were lower in both salivary glands of the LEV300 group compared to Control. Superoxide dismutase and glutathione peroxidase activities were lower in the salivary glands of treated animals compared to Control. In conclusion our data suggest that treatment with LEV represents a potentially toxic agent, that contributes to drug-induced salivary gland dysfunction.

Soluble epoxide hydrolase inhibitor, t-AUCB, improves salivary gland function by ameliorating endothelial injury

AIMS

Inhibitor of soluble epoxide hydrolase (t-AUCB) has been used in the experimental therapy of hypertension. This study aimed to investigate whether the secretion of submandibular glands (SMGs) altered in renal hypertensive rats, and to explore whether t-AUCB could improve the salivary secretion.

MAIN METHODS

2-kidney 1-clip Sprague-Dawley rats were used as renal hypertensive animals. t-AUCB treatment was given for 1 week after 8 weeks modeling. Blood pressure, blood perfusion and the secretion of SMGs, and endothelium-dependent relaxation of external maxillary artery were measured to investigate the effects of t-AUCB on the vascular tone and the secretion of SMGs in renal hypertensive rats. SMGs were collected for histological evaluation and the internal arteries were dissected for primary endothelial cells culture.

KEY FINDINGS

The blood perfusion and flow rate of SMGs in the renal hypertensive rats were significantly lower than those in the controls. Endothelium-dependent relaxation of the external maxillary artery and AMPK/Akt/eNOS signaling was impaired in hypertensive rats. The glandular morphology and the concentration of salivary ions did not change obviously. t-AUCB treatment ameliorated the secretion of SMGs, the blood perfusion, and the dysfunction of endothelium-dependent relaxation of the external maxillary artery by activating the AMPK/Akt/eNOS pathway in hypertensive rats.

SIGNIFICANCE

t-AUCB increases the blood perfusion through ameliorating dysfunction of endothelium-dependent relaxation of SMGs arteries and thus improves the hyposecretion of SMGs in hypertensive rats.

Nifedipine-induced histological changes in the parotid glands of hypertensive rats

Nifedipine is a widely used anti-anginal and anti-hypertensive agent. It is associated with significant gingival changes attributed more to collagen hyperplasia than to enhancement of protein synthesis. We investigated the influence of nifedipine on morphological changes in the parotid glands of rats in a model of hypertension. Twenty-eight male Wistar rats (8-10 weeks; 200±15 g) were divided into four groups (A-D). Hypertension was induced by surgical means in groups C and D. Animals in groups B and D were treated with nifedipine (0.85 mg/kg) via a gastroesophageal catheter the day after surgery (experimental day-1) for 2 weeks. A significant difference was observed between the control group and nifedipine group and between the control group and hypertension group with regard to the weight of the parotid gland and its surface area. Histological findings demonstrated changes in the parotid glands of hypertensive animals with mild vessel dilatation and infiltration of inflammatory cells. These histological findings seemed to be due more to changes in venous function than to alterations in gland architecture.

Associations between labial and whole salivary flow rates, systemic diseases and medications in a sample of older people

OBJECTIVE

To investigate the associations between age, gender, systemic diseases, medications and labial and whole salivary flow rates in older people.

METHODS

Unstimulated labial (LS) and unstimulated (UWS) and chewing-stimulated (SWS) whole salivary flow rates were measured in 389 randomly selected community-dwelling Danish women and 279 men aged 65-97 years. Systemic diseases, medications (coded according to the Anatomical Therapeutic Chemical (ATC) Classification System), tobacco and alcohol consumption were registered.

RESULTS

The number of diseases and medications was higher and UWS lower in the older age groups. On average, women were slightly older, had more diseases, higher medication intake and lower UWS, SWS and LS than men. High number of diseases and medications was associated with low UWS, SWS and LS. In the healthy (14%) and nonmedicated (19%) participants, flow rates were not associated with age and gender, apart from SWS being lower in nonmedicated women. Low UWS were associated with psychiatric and respiratory disorders, type 2 diabetes and intake of psycholeptics, psychoanaleptics (especially SRRIs), respiratory agents, oral antidiabetics (particularly sulfonylureas), magnesium-hydroxide, cardiac agents, quinine, thiazides, calcium channel blockers, statins, urinary antispasmodics, glucosamine, NSAIDs, opioids and ophthalmologicals. SWS were lower in participants with ophthalmological disorders using ophthalmologicals (especially antiglaucoma agents and miotics), but also in those taking antidepressants, cardiac agents (mostly digitalis glycosides) and calcium channel blockers. Cardiovascular diseases and intake of anti-thrombotics (mainly low dose aspirins), calcium channel blockers and oral antidiabetics were associated with low LS.

CONCLUSIONS

In older people, low salivary flow rates are associated with specific and high number of diseases and medications, but neither with age and gender per se nor with tobacco and alcohol consumption. Low UWS are associated with more diseases and medications than SWS and LS, which were primarily associated with cardiovascular diseases and medications including preventive agents such as low-dose aspirins and statins. New insights into medications and their association with salivary gland function were achieved using the ATC classification system.

Calcium antagonists cause dry mouth by inhibiting resting saliva secretion

Ca2+ antagonists cause dry mouth by inhibiting saliva secretion. The present study was undertaken to elucidate the mechanism by which Ca2+ antagonists cause dry mouth. Since the intracellular Ca2+ concentration ([Ca2+]i) is closely related to saliva secretion, [Ca2+]i was measured with a video-imaging analysis system by using human submandibular gland (HSG) cells as the material. The Ca2+ antagonist, nifedipine, inhibited the elevation in [Ca2+]i induced by 1-10 microM carbachol (CCh), but had no inhibitory effect on that induced by 30 and 100 microM CCh. The other kinds of Ca2+ antagonists, verapamil (10 microM), diltiazem (10 microM), and the inorganic Ca2+ channel blocker, CdCl2 (50 microM), also inhibited the [Ca2+]i elevation induced by 10 microM CCh. The Ca2+ channel activator, Bay K 8644 (5 microM), significantly enhanced the CCh (10 microM)-induced [Ca2+]i elevation. Endothelin-1 and norepinephrine also increased the CCh (10 microM)-induced [Ca2+]i elevation. SKF-96365 reversed the enhancement of the CCh (10 microM)-induced [Ca2+]i elevation caused by AlF4- and phenylephrine. The phospholipase Cbeta (PLCbeta) inhibitor, U-73122 (5 microM), significantly inhibited the [Ca2+]i elevation induced by 100 microM CCh compared with that induced by 10 microM CCh, while the PLCbeta activator, m-3M3FBS (20 microM), significantly increased the [Ca2+]i elevation induced by 100 microM CCh compared with that induced by 10 microM CCh. We therefore conclude that non-selective cation and voltage-dependent Ca2+ channels are involved in resting salivation and that Ca2+ antagonists depress H2O secretion by blocking the Ca2+ channels and thereby cause dry mouth.

Signaling pathways involved in pilocarpine-induced mucin secretion in rat submandibular glands

We have studied the signaling pathways involved in pilocarpine-induced mucin release in rat submandibular slices. Pilocarpine produced a significant increment of PGE2 levels and a positive (r=0.8870) and significant (p=0.0077) correlation between PGE2 production and mucin released was determined. The participation of PGE2 was confirmed by the use of indomethacin (indo) and of acetyl salicylic acid (ASA), cyclooxygenase inhibitors, which inhibited pilocarpine-induced mucin release. The muscarinic receptors involved in the regulation of mucin release were identified as M1 and M4 by the use of the selective acetylcholine receptors (mAChR) antagonists, pirenzepine, AF-DX 116, 4-DAMP and tropicamide. The secretory process was dependent on both, intracellular and extracellular calcium pools since it was inhibited by thapsigargin and verapamil. Cyclic AMP, nitric oxide synthase and PKC also participated in pilocarpine-induced mucin release. It is concluded that pilocarpine, by activation the M1 and M4 mAChR subtypes induces an increase of intracellular Ca2+ concentration ([Ca2+]I) and elevates cAMP levels, which in turn stimulates COX, PKC and NOS and promotes mucin exocytosis. PGE2 released induces cAMP accumulation which, together with PKC are involved in the PGE2 increased Ca2+/cAMP-regulated exocytosis. Thus, cAMP accumulation induced by cholinergic stimulation is, in part, the result of PGE2 production.

On the relation of nitric oxide to nifedipine-induced gingival hyperplasia and impaired submandibular glands function in rats in vivo

Calcium-channel blockers such as nifedipine could be associated with gingival overgrowth. The aim of this study was to examine the role of nitric oxide (NO) on nifedipine-induced gingival hyperplasia along with submandibular secretory function in rats. Animals in divided groups received nifedipine (250 mg/kg diet) alone and in combination with L-arginine (2.25% w/v) or N(omega)-nitro-L-arginine methyl ester (L-NAME) (0.7% w/v) in drinking water for 20 days. Controls received only tap water. Pure submandibular saliva was collected intraorally by micropolyethylene cannula and the mandibular gingiva was examined by means of dissecting microscope for signs of redness, thickness, inflammation and exuda. Twenty-day nifedipine treatment induced gingival hyperplasia accompanied with reduced salivary flow rate and concentrations of total protein, epidermal growth factor (EGF) and calcium in comparison with controls. Co-treatment of animals with nifedipine and L-arginine protected from gingival hyperplasia and retained flow rate, and concentrations of total protein, EGF and calcium in normal levels. Co-treatment of animals with nifedipine and L-NAME potentiated nifedipine-induced gingival hyperplasia and reductions in flow rate and concentrations of total protein, EGF, and calcium. It is concluded that nifedipine-induced gingival hyperplasia is associated with salivary dysfunction. Activation of cGMP-dependent positive signal-transduction mechanisms in salivary glands might be the mechanism for protective effects of NO against nifedipine-induced gingival hyperplasia.

Influence of castration on isoprenaline-induced amylase release in parotid gland from male rats

The purpose of this study was to determine the influence of testosterone, the male sex hormone, on beta-adrenergic agonist-induced amylase secretion from rat parotid glands. Isoprenaline (isoproterenol)-induced amylase secretion was measured in vitro from the parotid glands of control and castrated rats with and without testosterone replacement. The isoprenaline-induced amylase release was reduced in parotid glands from castrated rats compared to controls. The reduction of amylase release by isoprenaline in parotid glands of castrated rats, could be reversed by administration of testosterone. Furthermore, beta-adrenergic receptor density and the level of isoprenaline-evoked cAMP in parotid glands from castrated rats was lower compared to intact rats. Using SQ-22536 (an adenylyl cyclase inhibitor), dibutyryl cAMP (a cAMP analogue) and verapamil (a calcium channel blocker), we conclude that the impairment of amylase release from parotid glands after castration was not related to either adenylyl cyclase activity or cAMP accumulation. Amylase release from the parotid glands of castrated rats appears to be mediated by an increase in calcium ion influx.

Xerostomia and hyposalivation: causes, consequences and treatment in the elderly

Xerostomia and salivary gland hypofunction (SGH) are prevalent in elderly populations, causing much discomfort and even difficulties in eating. SGH also increases the occurrence and severity of oral diseases and makes the patient susceptible to candidiasis. The principal causes of SGH and xerostomia are systemic diseases and drugs used daily. The diagnosis of SGH and xerostomia is based on simple methods, of which measuring both unstimulated and stimulated salivary flow rate is the most important. Treatment calls for proper management of underlying disease, avoidance of all unnecessary medications, and topical remedies such as artificial saliva substitutes. However, good hydration is essential in the elderly with SGH and xerostomia, and water is the drink of choice. In extremely difficult cases, for instance in patients receiving radiotherapy for cancer of the head and neck regions, parasympathomimetic drugs may be administered if no contraindications exist.

Interaction between calcium channel blockers and sweetening agents on morphine-induced analgesia in mice by formalin test

1. Calcium is known to be an important ion in the modulation of nociception and inflammation. Previous research has shown that mice drinking sweet-tasting solutions such as sucrose, saccharin and aspartame exhibit significant changes in morphine-induced analgesia in both phases of the formalin test. 2. In this study, the role of calcium channel blockers on the effectivity of a 12-day regimen of different sweetening agents (sucrose 32%, saccharin 0.08% and aspartame 0.16%) on the alteration of the morphine response has been investigated. 3. Male albino mice weighing 20-27 g were used for experiments. Animals were given 12 days to adapt to dietary conditions. Animals were given morphine (1.5, 3, 6, 9 mg/kg) subcutaneously 30 min before observation. Nifedipine (5 mg/kg), verapamil (5 mg/kg) and diltiazem (10 mg/kg) were administered intraperitoneally 20 min before morphine injection. 4. Recording of the early phase started immediately and lasted for 10 min after formalin injection. Recording of the late response started 20 min after formalin injection and lasted for 10 min. 5. Calcium channel blockers potentiated the antinociceptive effects of sweetening agents and diminished the antagonistic effects of these compounds on morphine-induced analgesia in the early and late phases of the formalin test. 6. It is proposed that calcium has a role for the interactive effects of sweetening agents and morphine on pain sensitivity.

Clonidine-induced rhythmic activity in rabbit anococcygeus muscle

1. Clonidine 0.5 mM induced an extremely regular rhythmic activity in isolated rabbit anococcygeus muscle. The movements were resistant to tetrodotoxin effect. 2. Prazosin (5 x 10(-8)M-5 x 10(-6)M) and yohimbine (1.5 x 10(-7)M-5 x 10(-4)M) showed no remarkable effect on clonidine-induced rhythmic activity. 3. The clonidine-induced contractions were dependent on extracellular calcium and could be inhibited by the omission of calcium from medium or the introduction of verapamil (IC50 = 1.3 x 10(-7)M) or nifedipine (IC50 = 7.5 x 10(-8)M). 4. Pretreatment of animals with reserpine made the preparations 2800-fold more sensitive to this action of clonidine. 5. It can be concluded from this study that clonidine is able to induce rhythmic activity in rabbit anococcygeus muscle through a mechanism that increases intracellular concentration of Ca++ via membrane calcium channels.