Octreotide ameliorates alendronate-induced gastric injury

The preventive effect of Qing Dai on bisphosphonate-induced gastric cellular injuries

The Chinese herbal medicine Qing Dai has been traditionally used for the treatment of various inflammatory diseases. We previously reported that reactive oxygen species play an important role in bisphosphonate-induced gastrointestinal injuries and that Qing Dai improved ulcerative colitis by scavenging reactive oxygen species. In this study, we investigated whether Qing Dai prevented bisphosphonate-induced gastric cellular injuries. Risedronate (a bisphosphonate) was added to rat gastric mucosal cells. Risedronate-induced cellular injury, cellular lipid peroxidation, mitochondrial membrane potential, and reactive oxygen species production in rat gastric mucosal cells were examined via viable cell counting, specific fluorescent indicators, and electron spin resonance. Pretreatment with Qing Dai attenuated the fluorescence intensity of diphenyl-1-pyrenylphosphine and MitoSox as well as the signal intensities of electron spin resonance. Cell viability improved from 20% to 80% by pretreatment with Qing Dai. Thus, Qing Dai prevented this injury by suppressing mitochondrial reactive oxygen species production, which is the main cause of cellular lipid peroxidation. Qing Dai also maintained mitochondrial potential, reducing reactive oxygen species production. We conclude that Qing Dai has protective effects on bisphosphonate-induced gastrointestinal injury and thus has the potential for clinical application.

Pharmacokinetic and pharmacodynamic evidence for developing an oral formulation of octreotide against gastric mucosal injury

Among the somatostatin analogues, octreotide (OCT) is the most commonly used in clinic via intravenous or subcutaneous injection to treat various diseases caused by increased secretion of growth hormone, gastrin or insulin. In order to assesse the feasibility of developing oral formulations of OCT, we conducted systematical pharmacokinetic and pharmacodynamic analyses of OCT in several animal models. The pharmacokinetic studies in rats showed that intragastric administration of OCT had extremely low bioavailability (<0.5%), but it could specifically distribute to the gastric mucosa due to the high expression of somatostatin receptor 2 (SSTR2) in the rat stomach. The pharmacodynamic studies revealed that intragastric administration of OCT dose-dependently protected against gastric mucosal injury (GMI) in mice with WIRS-induced mouse gastric ulcers, which were comparable to those achieved by intravenous injection of OCT, and this effect was markedly attenuated by co-administration of CYN-154806, an antagonist of SSTR2. In pyloric ligation-induced ulcer mice, we further demonstrated that OCT significantly reduced the secretion of gastric acid via down-regulating the level of gastrin, which was responsible for the protective effect of OCT against GMI. Overall, we have provided pharmacokinetic and pharmacodynamic evidence for the feasibility of developing an oral formulation of OCT. Most importantly, the influence of SSTR2 on the pharmacokinetics and pharmacodynamics of OCT suggested that an oral formulation of OCT might be applicable for other clinical indications, including neuroendocrine neoplasms and pituitary adenoma due to the overexpression of SSTR2 on these tumor cells.

Protective Effects of Simvastatin Against Alendronate-Induced Gastric Mucosal Injury in Rats

BACKGROUND

It has been reported that simvastatin, a statin commonly prescribed for its anti-inflammatory and antioxidant effects, has gastroprotective effects in indomethacin and ethanol-induced gastric ulcers. However, the effects of simvastatin on alendronate-induced gastric mucosal injury remain unexplored.

AIM

This study investigated the use of simvastatin for the treatment of alendronate-induced gastric ulcers in rats.

METHODS

Female rats were pretreated with vehicle or simvastatin (20 and 60 mg/kg p.o.). After 1 h, the rats received alendronate (50 mg/kg p.o.). Simvastatin was administered once daily for 7 days, and from the fourth day of simvastatin treatment, alendronate was administered once daily for 4 days. On the final day of treatment, 4 h after alendronate administration, animals were euthanized, their stomachs were removed, and gastric damage was measured. Samples of the stomach were fixed in 10 % formalin immediately after their removal for subsequent histopathological assessment. Unfixed samples were weighed, frozen at -80 °C until assayed for glutathione (GSH), malondialdehyde (MDA), and cytokine levels and myeloperoxidase (MPO) activity. A third group was used to measure mucus and gastric secretion.

RESULTS

Pretreatment with simvastatin prevented alendronate-induced macroscopic gastric damage and reduced the levels of MDA and GSH, TNF-α and IL-1β, MPO activity, and mucus levels, in the stomach.

CONCLUSIONS

This study demonstrates the protective effects of simvastatin against alendronate-induced gastric ulceration. Maintenance of mucosal integrity, inhibition of neutrophil activity, and reduced oxidative stress associated with decreased gastric acidity may explain the gastroprotective effects of simvastatin.

Pharmacokinetic and therapeutic efficacy of intrapulmonary administration of zoledronate for the prevention of bone destruction in rheumatoid arthritis

Zoledronate, a third-generation nitrogen-containing bisphosphonate, is a new therapeutic agent for the prevention of joint destruction in rheumatoid arthritis (RA). Due to the poor oral absorption of zoledronate, the intravenous route has been the preferred method of administration. To evaluate whether the lung is a promising alternative route of zoledronate administration for the prevention of joint destruction in RA, we examined the pharmacokinetics, safety and therapeutic potential of zoledronate after intrapulmonary administration. The bioavailability of zoledronate was 55% after intrapulmonary administration in rats. In a collagen-induced RA mouse model, an intrapulmonary administration of zoledronate given 7 d before the 2nd collagen immunization effectively suppressed bone loss and joint destruction to a level similar to that achieved with intravenous injection at 21 d after the 2nd collagen immunization. Zoledronate only slightly affected lactate dehydrogenase activity in bronchoalveolar lavage fluid 4 h after intrapulmonary administration of the therapeutic dose in rats. Moreover, zoledronate only slightly changed the plasma level of creatinine after intrapulmonary administration while creatinine significantly increased after intravenous injection of zoledronate in mice. These results indicate that the lung is a promising alternative route of zoledronate administration for the treatment and prevention of joint destruction in RA.

GM crops and the rat digestive tract: a critical review

The aim of this review is to examine the relationship between genetically modified (GM) crops and health, based on histopathological investigations of the digestive tract in rats. We reviewed published long-term feeding studies of crops containing one or more of three specific traits: herbicide tolerance via the EPSPS gene and insect resistance via cry1Ab or cry3Bb1 genes. These genes are commonly found in commercialised GM crops. Our search found 21 studies for nine (19%) out of the 47 crops approved for human and/or animal consumption. We could find no studies on the other 38 (81%) approved crops. Fourteen out of the 21 studies (67%) were general health assessments of the GM crop on rat health. Most of these studies (76%) were performed after the crop had been approved for human and/or animal consumption, with half of these being published at least nine years after approval. Our review also discovered an inconsistency in methodology and a lack of defined criteria for outcomes that would be considered toxicologically or pathologically significant. In addition, there was a lack of transparency in the methods and results, which made comparisons between the studies difficult. The evidence reviewed here demonstrates an incomplete picture regarding the toxicity (and safety) of GM products consumed by humans and animals. Therefore, each GM product should be assessed on merit, with appropriate studies performed to indicate the level of safety associated with them. Detailed guidelines should be developed which will allow for the generation of comparable and reproducible studies. This will establish a foundation for evidence-based guidelines, to better determine if GM food is safe for human and animal consumption.

Alendronate induces gastric damage by reducing nitric oxide synthase expression and NO/cGMP/K(ATP) signaling pathway

Chronic use of alendronate has been linked to gastrointestinal tract problems. Our objective was to evaluate the role of the NO/cGMP/KATP signaling pathway and nitric oxide synthase expression in alendronate-induced gastric damage. Rats were either treated with the NO donor, sodium nitroprusside (SNP; 1, 3, and 10 mg/kg), or the NO synthase (NOS) substrate, L-arginine (L-Arg; 50, 100, and 200 mg/kg). Some rats were pretreated with either ODQ (a guanylate cyclase inhibitor; 10 mg/kg) or glibenclamide (KATP channels blocker; 10 mg/kg). In other experiments, rats were pretreated with L-NAME (non-selective NOS inhibitor; 10 mg/kg), 1400 W (selective inducible NOS [iNOS] inhibitor; 10 mg/kg), or L-NIO (a selective endothelial NOS [eNOS] inhibitor; 30 mg/kg). After 1 h, the rats were treated with alendronate (30 mg/kg) by gavage for 4 days. SNP and L-Arg prevented alendronate-induced gastric damage in a dose-dependent manner. Alendronate reduced nitrite/nitrate levels, an effect that was reversed with SNP or L-Arg treatment. Pretreatment with ODQ or glibenclamide reversed the protective effects of SNP and L-Arg. L-NAME, 1400 W, or L-NIO aggravated the severity of alendronate-induced lesions. In addition, alendronate reduced the expression of iNOS and eNOS in the gastric mucosa. Gastric ulcerogenic responses induced by alendronate were mediated by a decrease in NO derived from both eNOS and iNOS. In addition, our findings support the hypothesis that activation of the NO/cGMP/KATP pathway is of primary importance for protection against alendronate-induced gastric damage.

The hydrogen sulfide donor, Lawesson's reagent, prevents alendronate-induced gastric damage in rats

Our objective was to investigate the protective effect of Lawesson's reagent, an H2S donor, against alendronate (ALD)-induced gastric damage in rats. Rats were pretreated with saline or Lawesson's reagent (3, 9, or 27 µmol/kg, po) once daily for 4 days. After 30 min, gastric damage was induced by ALD (30 mg/kg) administration by gavage. On the last day of treatment, the animals were killed 4 h after ALD administration. Gastric lesions were measured using a computer planimetry program, and gastric corpus pieces were assayed for malondialdehyde (MDA), glutathione (GSH), proinflammatory cytokines [tumor necrosis factor (TNF)-α and interleukin (IL)-1β], and myeloperoxidase (MPO). Other groups were pretreated with glibenclamide (5 mg/kg, ip) or with glibenclamide (5 mg/kg, ip)+diazoxide (3 mg/kg, ip). After 1 h, 27 µmol/kg Lawesson's reagent was administered. After 30 min, 30 mg/kg ALD was administered. ALD caused gastric damage (63.35 ± 9.8 mm(2)); increased levels of TNF-α, IL-1β, and MDA (2311 ± 302.3 pg/mL, 901.9 ± 106.2 pg/mL, 121.1 ± 4.3 nmol/g, respectively); increased MPO activity (26.1 ± 3.8 U/mg); and reduced GSH levels (180.3 ± 21.9 µg/g). ALD also increased cystathionine-γ-lyase immunoreactivity in the gastric mucosa. Pretreatment with Lawesson's reagent (27 µmol/kg) attenuated ALD-mediated gastric damage (15.77 ± 5.3 mm(2)); reduced TNF-α, IL-1β, and MDA formation (1502 ± 150.2 pg/mL, 632.3 ± 43.4 pg/mL, 78.4 ± 7.6 nmol/g, respectively); lowered MPO activity (11.7 ± 2.8 U/mg); and increased the level of GSH in the gastric tissue (397.9 ± 40.2 µg/g). Glibenclamide alone reversed the gastric protective effect of Lawesson's reagent. However, glibenclamide plus diazoxide did not alter the effects of Lawesson's reagent. Our results suggest that Lawesson's reagent plays a protective role against ALD-induced gastric damage through mechanisms that depend at least in part on activation of ATP-sensitive potassium (KATP) channels.

Levels of MDA and SOD in acute gastric mucosal injury in rats exposed to positive acceleration

AIM: To determine the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in acute gastric mucosal injury in rats exposed to positive acceleration (+Gz), observe the impact of +Gz exposure on gastric mucosal injury, and clarify the role of oxygen free radicals in this process.

METHODS: Thirty male SD rats were randomly divided into three groups: A (ethanol), B (ethanol with +5Gz exposure), and C (ethanol with +10Gz exposure). All rats were intragastrically given ethanol (0.4 mL/100 mg) after 24 h of fasting and water deprivation for 12 h. One hour after ethanol administration, group A did not undergo +Gz, while groups B and C were continuously exposed to +5Gz and +10Gz for 3 minutes, respectively. Immediately after +Gz exposure, gastric tissue samples were taken to observe gastric mucosal injury by light microscopy. The indexes of gastric mucosal injury were calculated, and the contents of MDA and SOD in the gastric mucosa were determined by ELISA.

RESULTS: Gastric mucosal injury was observed in all the groups, and gastric mucosal injury was most severe in group C, followed by groups B and A. Group A had mildest gastric mucosal injury. Group B showed visible gastric mucosal congestion, edema and scattered bleeding spots, and light microscopy revealed acute inflammatory cell infiltration. The indexes of gastric mucosal injury were significantly higher in group B than in group A (naked eye: 23.654 ± 9.678 vs 11.410 ± 3.742; light microscopy: 5.000 ± 1.054 vs 3.800 ± 1.399; both P < 0.05). Group C had heaviest gastric mucosal injury. Diffuse gastric mucosal congestion, edema, erosion and many bleeding spots were visible, and light microscopy revealed disorderly arranged gland structure, interstitial congestion, erosion, and acute inflammatory cell infiltration. The indexes of gastric mucosal injury were significantly higher in group C than in groups A and B (naked eye: 49.080 ± 10.254, light microscopy: 9.400 ± 2.011; all P < 0.05). Compared with group A, the content of MDA in the gastric mucosa did not rise significantly in group B (0.255 ± 0.074 vs 0.235 ± 0.044, P > 0.05); however, MDA content in group C (0.376 ± 0.084) was significantly higher than those in groups A and B (both P < 0.05). The content of SOD in the gastric mucosa was significantly lower in group C than in groups A and B (8.852 ± 1.001 vs 10.000 ± 1.067, 10.694 ± 0.965, P < 0.05), although no significant difference was observed between the latter two groups (P > 0.05).

CONCLUSION: +Gz exposure aggravates acute gastric mucosal injury in rats possibly by altering the contents of MDA and SOD in gastric tissue.

Development of a novel self-dissolving microneedle array of alendronate, a nitrogen-containing bisphosphonate: evaluation of transdermal absorption, safety, and pharmacological effects after application in rats

Alendronate is a nitrogen-containing bisphosphonate that is widely used for the treatment of osteoporosis. In this study, we developed a novel self-dissolving micron-size needle array (microneedle array) containing alendronate, which was fabricated by micromodeling technologies using hyaluronic acid as a basic material. Micron-scale pores in the skin were seen after the application of the alendronate-loaded microneedle array, verifying establishment of transdermal pathways for alendronate. The absorption of alendronate after the application of alendronate-loaded microneedle array was almost equivalent to that after subcutaneous administration, and the bioavailability of alendronate was approximately 90% in rats. Furthermore, delivery of alendronate via this strategy effectively suppressed the decrease in the width of the growth plate in a rat model of osteoporosis. Although mild cutaneous irritation was observed after the application of the alendronate-loaded microneedle array, it resolved by day 15. These findings indicate that this alendronate-loaded microneedle array is a promising transdermal formulation for the treatment of osteoporosis.

The effect of alendronate sodium on human erythrocytes

Alendronate sodium is a medicine, which is commonly used in osteoporosis treatment. Nowadays, this substance is given to patients in tablets, but in future it is planned that it will be administrated into human organisms as intravenous infusions; therefore, significant interactions of this medicine with erythrocytes will be inevitable. It is the reason why we decided to investigate the interaction of alendronate sodium with human erythrocytes. The effect of this medicine on acetylcholinesterase activity, lipid and protein peroxidation, as well as cellular thiol content was examined. Moreover, the effect of alendronate sodium on alterations in erythrocytes morphology was assessed. Human erythrocytes were incubated with alendronate sodium in the concentrations ranging from 0.33 to 100 μM for 1 h and 24 h. No changes have been observed in the parameters examined after 1h of incubation of the erythrocytes with this medicine excluding the carbonyl groups level. Moreover, no alterations in the activity of acetylcholinesterase, the level of thiols as well as in morphology of the erythrocytes incubated with alendronate sodium for 24h have been observed. It was also proven that alendronate sodium increased the level of reactive oxygen species (ROS) but only after 24h of incubation. We have not observed any severe changes in cells studied even at the highest dose of bisphosphonates examined, thus their usage should not be dangerous for the erythrocytes of people treated with these medicines.

Octreotide ameliorates gastric lesions in chronically mild stressed rats

AIM: To evaluate the effect of chronic mild stress (CMS) on the emergence of gastric ulcers and possible modulation by octreotide, a synthetic somatostatin analogue.

METHODS: Adult male Wistar rats were subjected to nine different unpredictable random stress procedures for 21 d, a multifactorial interactional animal model for CMS. Octreotide was administered daily for 21 d at two dose levels (50 and 90 μg/kg) before exposure to stress procedure. Macro- and microscopical assessments were made, in addition to quantification of plasma corticosterone and gastric mucosal inflammatory, oxidative stress, and apoptotic biomarkers.

RESULTS: Exposure to CMS elevated plasma corticosterone (28.3 ± 0.6 μg/dL, P = 0.002), an event that was accompanied by gastric lesions (6.4 ± 0.16 mm, P = 0.01) and confirmed histopathologically. Moreover, the insult elevated gastric mucosal lipid peroxides (13 ± 0.5 nmol/g tissue, P = 0.001), tumor necrosis factor-α (3008.6 ± 78.18 pg/g tissue, P < 0.001), prostaglandin E2 (117.1 ± 4.31 pg/g tissue, P = 0.002), and caspase-3 activity (2.4 ± 0.14 OD/mg protein, P = 0.002). Conversely, CMS mitigated interleukin-10 (627.9 ± 12.82 pg/g tissue, P = 0.001). Furthermore, in animals exposed to CMS, octreotide restored plasma corticosterone (61% and 71% from CMS, P = 0.002) at both dose levels. These beneficial effects were associated with a remarkable suppression of gastric lesions (38% and 9% from CMS, P = 0.01) and reversal of derangements in gastric mucosa.

CONCLUSION: The current investigation provides evidence that exposure to CMS induces gastric ulceration, which was alleviated by administration of octreotide possibly possessing antioxidant, anti-inflammatory, and anti-apoptotic actions.

Development of a novel transdermal patch of alendronate, a nitrogen-containing bisphosphonate, for the treatment of osteoporosis

Bisphosphonates are widely used for the treatment and prevention of bone diseases, including Paget disease, hypercalcemia of malignancy, and postmenopausal osteoporosis. In this study, we developed a novel transdermal patch of alendronate, a nitrogen-containing bisphosphonate, for the treatment of bone diseases. The maximum permeation fluxes of alendronate through rat and human skin after application of this patch were 1.9 and 0.3 µg/cm(2) per hour, respectively. The bioavailability (BA) of alendronate in rats was approximately 8.3% after the application of alendronate patch and approximately 1.7% after oral administration. These results indicated that the transdermal permeation of alendronate using this patch system was sufficient for the treatment of bone diseases. The plasma calcium level was effectively reduced after application of the alendronate patch in 1α-hydroxyvitamin D(3) -induced hypercalcemia model rats. The alendronate patch also effectively suppressed the decrease in bone mass in model rats with osteoporosis. Modest alendronate-induced erythema of rat skin was observed after application of the alendronate patch. Incorporation of butylhydroxytoluene in the alendronate patch almost completely suppressed this alendronate-induced skin damage while maintaining the transdermal permeation and pharmacologic effects of alendronate. These findings indicate that our novel transdermal delivery system for alendronate is a promising approach to improve compliance and quality of life of patients in the treatment of bone diseases.

Effect of Lonicerae Flos extracts on reflux esophagitis with antioxidant activity

AIM: To observe the effects of traditional antiinflammatory medicine Lonicerae Flos (LF) on rat reflux esophagitis (RE) induced by pylorus and forestomach ligation compared with the well-known proton antioxidant, α-tocopherol.

METHODS: Rats were pretreated with three different dosages of LF (500, 250 and 125 mg/kg) orally, once a day for 14 d before pylorus and forestomach ligation. Nine hours after pylorus and forestomach ligation, changes to the stomach and esophagus lesion areas, gastric volumes, acid and pepsin outputs, antioxidant effects, esophageal lipid peroxidation, superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), myeloperoxidase and glutathione (GSH) levels, and collagen contents (marker of flexibility) were observed on the esophageal and fundic histopathology. The results were compared with an α-tocopherol (once orally, 1 h before operation, 30 mg/kg) treated group in which the effects on RE were already confirmed.

RESULTS: Pylorus and forestomach ligations caused marked increases of gross esophageal and gastric mucosa lesion areas, which corresponded with histopathological changes. In addition, increases of esophageal lipid peroxidation, decreases of SOD, CAT, and GSH-free radical scavengers, increases of collagen were observed. However, these pylorus and forestomach ligation induced RE were dose-dependently inhibited by treatment of 500, 250 and 125 mg/kg of LF extract, mediated by antioxidant effects. RE at 250 mg/kg showed similar effects α-tocopherol.

CONCLUSION: The results suggest that antioxidant effects of LF could attenuate the severity of RE and prevent the esophageal mucosal damage, and validate its therapeutic use in esophageal reflux disease.

Clodronic acid formulations available in Europe and their use in osteoporosis: a review

Clodronic acid (Cl(2)-MBP [dichloromethylene bisphosphonic acid], clodronate) is a halogenated non-nitrogen-containing bisphosphonate with antiresorptive efficacy in a variety of diseases associated with excessive bone resorption. The drug is believed to inhibit bone resorption through induction of osteoclast apoptosis, but appears also to possess anti-inflammatory and analgesic properties that contrast with the acute-phase and inflammatory effects seen with nitrogen-containing bisphosphonates. Clodronic acid has been shown to be effective in the maintenance or improvement of bone mineral density when given orally, intramuscularly or intravenously in patients with osteoporosis. Use of the drug is also associated with reductions in fracture risk. The intramuscular formulation, which is given at a dose of 100 mg weekly or biweekly, is at least as effective as daily oral therapy and appears more effective than intermittent intravenous treatment. Intramuscular clodronic acid in particular has also been associated with improvements in back pain. The drug is well tolerated, with no deleterious effects on bone mineralization, and use of parenteral therapy eliminates the risk of gastrointestinal adverse effects that may be seen in patients receiving bisphosphonate therapy.

Effect of acid secretion blockade on acute gastric mucosal lesions induced by Tityus serrulatus scorpion toxin in anaesthetized rats

Scorpion venom (TX) promotes gastric acid and pepsin secretion leading to acute gastric mucosal lesions (AGML), when injected in animals. The goal of the present study was to observe the effects of acid gastric secretion blockers over the incidence of TX-induced AGML in vivo. To verify this model, we used male albino rats, fasted 18-20 h (n=122) and anaesthetized with urethane (1.4 g/kg, i.p.). Their trachea and left femoral vein were both cannulated; the first to avoid airway obstructions during scorpion intoxication and the second for administration of saline, TX and acid blockers. Following the surgical procedure, the animals were divided in 10 groups of at least 10 animals each. Control groups were injected with NaCl 0.9% 1 ml/kg (n=10) or TX 375 microg/kg (n=32). Test groups (n=10, each) received atropine 5 mg/kg, cimetidine 10mg/kg, ranitidine 2.5mg/kg, ranitidine 5mg/kg, omeprazol 1 mg/kg, omeprazol 4 mg/kg, octreotide 80 and octreotide 100 microg/kg 10 min before the TX was injected. After 1h of intoxication, the stomach was resected for macroscopic study and the gastric secretion was collected for volume, pH and acid output assessment. We observed that all blockers were able to completely or partially prevent the TX-induced acid secretion as well as the AGML (p<0.05). Our data suggest the TX-induced AGML can be prevented by different class of acid blockers injected before the intoxication.

Drug injury in the upper gastrointestinal tract: effects of alendronate

Osteoporosis is a disease characterized by an increase in bone resorption and a decline in bone density, which leads to increased susceptibility to bone fractures. Long-term therapy is needed to increase bone mineral density and maintain bone strength. Safe and well-tolerated medical therapies are required for long-term maintenance. Alendronate, an oral bisphosphonate, has been used for treatment of osteoporosis since the mid 1990s; however, recent studies have suggested alendronate can have significant gastrointestinal side effects. Most data suggest that the risk of these effects is low and not significantly higher than with placebo but there are limited reports that suggest otherwise, in both clinical trials and animal studies. Alendronate continues to remain an important mainstay of osteoporosis therapy.

Protective effect of taurine against alendronate-induced gastric damage in rats

Alendronate (ALD) causes serious gastrointestinal adverse effects. The aim of this study was to investigate whether taurine (TAU), a semi-essential amino acid and an antioxidant, improves the alendronate-induced gastric injury. Rats were administered 20 mg/kg ALD by gavage for 4 days, either alone or following treatment with TAU (50 mg/kg, i.p.). On the last day of treatment, following drug administration, pylorus ligation was performed and 2 h later, rats were killed and stomachs were removed. Gastric acidity and tissue ulcer index values, lipid peroxidation and glutathione (GSH) levels, myeloperoxidase (MPO) activity as well as the histologic appearance of the stomach tissues were determined. Chronic oral administration of ALD induced significant gastric damage, increasing lipid peroxidation, MPO activity and collagen content, as well as decreasing tissue GSH levels. Treatment with TAU prevented the damage and also the changes in biochemical parameters. Findings of the present study suggest that ALD induces oxidative gastric damage by a local irritant effect, and that TAU ameliorates this damage by its antioxidant and/or membrane-stabilizing effects.

Clinical endocrinology and metabolism. The somatostatin neuroendocrine system: physiology and clinical relevance in gastrointestinal and pancreatic disorders

Somatostatin is produced in enteroendocrine D cells and intrinsic neurons of the stomach, intestines and pancreas. Its physiologic actions are mediated primarily by somatostatin receptors type 2 and 5, and include the inhibition of secretion of most endocrine and exocrine factors. Diseases directly attributable to somatostatin excess or deficiency are rare, although there is a complex pathogenic relationship between persistent Helicobacter pylori infection and reduced somatostatin in chronic gastritis. Abundant somatostatin receptors on many neoplastic and inflammatory cells are the basis for sensitive in vivo imaging with radiolabeled somatostatin analogs and provide a therapeutic target. Current indications for somatostatin therapy include hormone-expressing neuroendocrine tumors, intractable diarrhea and variceal bleeding secondary to portal hypertension. Exciting advances are being made in the development of high-affinity nonpeptide analogs with receptor-subtype selectivity and increased bioavailability. Somatostatin analogs coupled to high-energy radionuclides show promise as novel cytotoxic agents for certain metastatic tumors.