Interaction between warfarin and nonsteroidal anti-inflammatory drugs (NSAIDs) in rats

In fed rats, the following NSAIDs were administered orally 24 hr before or 18 hr after the intraperitoneal administration of 1.34 mg/kg warfarin: phenylbutazone, 150 mg/kg; diflunisal, 75 mg/kg; ibuprofen, 150 mg/kg; acetylsalicylic acid, 300 mg/kg; indomethacin, 8 mg/kg; tolmetin sodium, 50 mg/kg; ketoprofen, 8 mg/kg; and amfenac sodium, 8 mg/kg. The elevation of the 24-hr prothrombin time was indicative of the effect of the warfarin. Warfarin-treated fasted rats showed a significantly higher prothrombin time than warfarin-treated fed rats. Interaction with phenylbutazone and warfarin occurred in fed and not in fasted rats when administered 18 hr after administration of the warfarin. At the 24-hr pretreatment time, only phenylbutazone significantly reduced the elevated prothrombin time. With the exception of amfenac sodium, all the NSAIDs significantly enhanced the elevated prothrombin time when administered 18 hr after warfarin. Their decreasing order of activity in enhancing the elevated prothrombin time was phenylbutazone, diflunisal, acetylsalicylic acid, ibuprofen, indomethacin, tolmetin sodium, and ketoprofen. The results indicate that the rat is more sensitive than the human to the interaction between warfarin and NSAIDs.     

Effect of bromocriptine,a dopamine receptor agonist,on the experimentally induced gastric ulcers in albino rats

The effect of bromocriptine, a dopamine receptor agonist, has been studied on the aspirin, phenylbutazone and reserpine induced gastric ulcers in rats. A single dose of bromocriptine 4 mg/kg s.c. produced a significant exacerbation of gastric ulcers induced by all the three ulcerogenic drugs, whereas in the same dose administered once daily for 5 consecutive days, it produced a marked protective effect in all the models. A review of the literature shows that different mechanisms may be involved in the opposite effects of acutely and chronically administered bromocriptine observed in this study. The study also points towards a role of dopamine in the pathogenesis of gastroduodenal ulceration.     

Effects of oral administration of PGE2 on gastric secretion and experimental peptic ulcerations

The anti-secretory and anti-ulcer effects of prostaglandin E₂ (PGE₂) using iso-osmotic buffer as a vehicle have been investigated in several types of laboratory animals. Orally administered PGE₂ was found to be highly effective in preventing formation of ulcers in several experimental models -- pylorus ligated induced ulcers in rats, histamine induced ulcers in guinea pigs, reserpine induced ulcers in rats and pentagastrin induced ulcers in guinea pigs and cats. PGE₂ also suppressed acid secretion but not pepsin activity. It was concluded that the anti-ulcer effects of PGE₂ were due to its anti-secretory activity rather than antipepsin activity. In view of PGE₂'s activity in preventing ulceration induced by histamine and reserpine in addition to pentagastrin, it is suggested that the anti-pentagastrin activity of PGE₂ is not specific.     

Untersuchungen zum Einfluß von Jahreszeit und Wetter auf das experimentelle Magenulkus der Ratte

Three different models for the induction of gastric ulcers in rats (phenylbutazone, 200 mg/kg; swimming, 3 × 30 min, water temperature 26–27°C; immobilization, 30 hours) were used to investigate the influence of weather and season. In a systematic study experiments were carried out weekly over a period of one year with male (phenylbutazone, immobilization) and female (swimming) rats of the same age kept under controlled conditions. The highest incidence of gastric ulcers was found in the swimming test; the lowest in the immobilization test. Maximum and minimum gastric ulcer rates were observed for each test but at different times. There was no uniform seasonal pattern. With decreasing atmospheric pressure a higher incidence of gastric ulcers was found 24 hours before the phenylbutazone and immobilization tests. Low atmospheric pressure and high relative humidity during the phenylbutazone and swimming tests also caused a higher incidence of gastric lesions (P<0.05). No correlation was found between the other meteorological conditions and the incidence of gastric ulcer.     

The influence of weather and climate on the incidence of gastric ulcers after reserpine in rats

Each month over a period of 22 months two groups of female rats were given i.p. 2.5 mg reserpine/kg BW and the number of gastric ulcers/rat were counted 24 h later. One group (n = 40) was kept for 17 days under environmentally controlled conditions (temperature, humidity, light intensity, length of photoperiod) while the other group (n = 40) was maintained for the same 17 days in a room near the open window under uncontrolled conditions. Under uncontrolled conditions gastric ulcer rate was negatively correlated with T_a (r=–0.87), T_a+T_wb(r=–0.84), and T_eq=T_a+2e (r=–0.83) of the last 24 hours. The correlation coefficients were higher with meteorological data of the 24 hours after administration of reserpine than with the data of the previous 16 days. No seasonal variation of ulcer morbidity was observed in the rats kept under controlled conditions. Hence, in rats, reserpine increases the gastric ulcer rate in the cold. Serious errors might arise in the interpretation of experiments when the rats are not housed under environmentally controlled conditions.     

The influence of exposure to cold on the incidence of gastric ulcers after reserpine in rats

Groups of female rats (n=20) exposed from 0 to 13 days to T_a's from 8.0° to 29.0°C were given 2.5 mg/kg reserpine i.p.; T_re and gastric ulcers (GU) were recorded 24 h afterwards. At exposure temperatures below 21.0°C there was a highly significant positive correlation between T_a and T_re (r=0.85) and a negative correlation between T_a and GU (r=–0.92). The GU rate after reserpine was not affected by temperatures above 21°C up to 29°C. Below 16.5°C a difference of the reserpine response was found between rats with less and more than 3 days acclimation to a given T_a. In rats with less than 3 days acclimation the mean T_re after reserpine was 1.0°C lower and the mean GU rate was 1.7 ulcers/rat higher than in rats with more than 3 days acclimation. The correlation of T_re with GU rate revealed that the mean number of GU increased with decreasing T_re · T_re and GU were negatively correlated in both series of experiments: r= –0.92 for non-acclimated rats and r= –0.95 for >3d acclimated rats. Cold acclimation of rats for 8 days at 13.0 °C or 13 days at 10.0 °C did not significantly affect T_re and the GU rate if the rats were taken to 21.0°C after reserpine administration. The results show that with and without cold-acclimation the extent of hypothermia in rats after a standard reserpine dose depends on the prevailing ambient temperature below the comfort range and the GU rate depends on the extent of the hypothermia.     

Interrelation between the analgesic and ulcerogenic action of cysteamine

Interrelationship was studied between the influence of cysteamine on pain threshold and ulcerogenic effect on the duodenum. Cysteamine (350 mg/kg) induced analgesia in mice which was prevented by naloxone (1.5 mg/kg). In rats, cysteamine produced duodenal ulcers with concomitant analgesia. The intensity of ulceration was higher in animals with lower basal pain threshold. The correlation between central and peripheral effects of endogenous opioids in the development of experimental duodenal ulcers is discussed.     

Aspirin, age, and proximity to lymphoid nodules influence cell proliferation parameters in rat colonic crypts

Recent epidemiological studies have demonstrated a correlation between regular aspirin (acetylsalicylic acid) use and decrease risk for the development of fatal colorectal cancer. An increase in the size of the cell proliferation compartment in colorectal crypts has been correlated with an increased risk for the development of colon cancer in animals and in humans. To determine if acetylsalicylic acid acts to decrease the size of the cell proliferation compartment, young (3 month) and old (22 month) rats were treated intragastrically with: 1 the vehicle for acetylsalicylic acid delivery (0.25% wt/vol carboxymethylcellulose in 0.15 N HCI), 2 a single dose of acetylsalicylic acid (100 mg/kg), or 3 acetylsalicylic acid (30 mg/kg) given daily for 30 days. One day after the last treatment, colons were resected, fixed, sectioned and mounted on slides for immunohistochemical staining with a monoclonal antibody to proliferating cell nuclear antigen to assess cell proliferation parameters in the colonic crypts. The results were subjected to three way analysis of variance to assess the effects of: 1 rat age, 2 acute or chronic acetylsalicylic acid treatment, and 3 location of crypts over and away from aggregates of lymphoid nodules on the crypt proliferative parameters. Results demonstrated that: 1 acetylsalicylic acid treatment caused an overall decrease in the proliferative zone height, as measured in number of cells in the crypt column, 2 that crypts located over aggregates of lymphoid nodules had significantly higher proliferative activity than crypts located away from aggregates of lymphoid nodules, and 3 after chronic acetylsalicylic acid treatment there was a greater suppression of proliferative zone height in the crypts of old rats than in the crypts of young rats. In conclusion, acute and chronic intragastric delivery of acetylsalicylic acid caused an overall downward shift in the cell proliferation compartment of colonic crypts of young and of old rats. Whether or not acetylsalicylic acid administration will cause the same proliferative zone height response in carcinogen-treated rats is not yet established.     

Inhibition of arachidonate- and escherichia coli-induced enteropooling in the rat by acetylsalicylic acid and similar drugs

Some foods and laxatives stimulate prostanoid biosynthesis and this effect is inhibited by acetylsalicylate (1); prostanoid administration causes diarrhoea and other symptoms of gut dysfunction (2,3,4). We therefore studied the effects of arachidonic acid, prostaglandins E₁ and E₂, endotoxin, laxatives and cyclooxugenase inhibitors in the rat ‘enteropooling’ test (5). All drugs were given orally. Prostaglandin E₂ (0.2mg/ kg), prostaglandin E₁ (0.74mg/kg), arachidonic acid (129mg/kg), castor oil (0.42ml/kg), magnesium sulphate (37mg/kg) and endotoxin (39.5mg/kg) doubled intestinal fluid volume. Cyclooxygenase inhibitors reduced arachidonate-induced enteropooling (indomethacin > acetylsalicylic acid > paracetamol > sodium salicylate > bismuth subsalicylate). Acetylsalicylic acid inhibited endotoxin-, castor oil-, but not prostaglandin E₂-or magnesium sulphate-induced enteropooling. Because acetylsalicylic acid was unexpectedly active in this test, we suggest that it may prove useful for the treatment of ‘travellers’ diarrhoea.     

The gastric ulcer protective effect of boswellic acids, a leukotriene inhibitor from Boswellia serrata, in rats

Aim of the study is to evaluate the anti-ulcer efficacy of the boswellic acids (BA), a triterpenoid known as anti-inflammatory/anti-arthritic agent, which is in clinical use. The reason for the study is that, the known non-steroidal anti-inflammatory drugs (NSAIDs) are full of side effects especially ulceration which is at the top. BA, although, used as an anti-arthritic agent yet it is not only devoid of ulcer production but protective also. The activity evaluation was done by the following universally accepted animal models viz., pyloric ligation, ethanol–HCl, acetylsalicylic acid, indomethacin and cold restrained stress-induced ulceration in rats. Results of the present study revealed that BA possess a dose dependent antiulcer effect against different experimental models. It showed different degree of inhibition of the ulcer score towards different ulcerogenic agents. The ulcer score against various ulcer inducing agents viz., pyloric ligation, ethanol/HCl, (acute and chronic) acetylsalicylic acid, indomethacin and cold restraint stress, was inhibited by 39%, 38%, 51%, 31%, 37% and 42% respectively at 250 mg/kg. From the data it is concluded that BA inhibited ulcer production non-specifically in all the experimental models, whereby, it is not possible to propose a single specific mechanism. Nevertheless it is possible that BA might be acting by increasing the gastric mucosal resistance and local synthesis of cytoprotective prostaglandins and inhibiting the leukotriene synthesis.     

Effects of chemically- and environmentally-induced hypothermia on micronucleus induction in rats

We investigated micronucleus induction in rats treated with chlorpromazine and reserpine, drugs that induce hypothermia. We administered chlorpromazine (31.3--250mg/kg) or reserpine (500--2000 mg/kg) intraperitoneally and measured temperature rectally. Chlorpromazine at 62.5-250mg/kg and reserpine at all doses significantly decreased rectal temperature, although the hypothermic response was weaker than previously reported in mice. Only chlorpromazine at 250mg/kg decreased rectal temperature transiently to <33 degrees C for 20h and induced a statistically significant increase in micronucleated polychromatic erythrocyte frequency. When rats treated with reserpine at 500mg/kg were exposed to an environmental temperature of 16 degrees C for 6, 12, or 24h to keep their body temperature under 33 degrees C, only the 24h treatment group significantly induced micronuclei. In addition, relatively large micronuclei (diameter of micronucleus> or = 1/4 diameter of cytoplasm) accounted for 33.0% of the induced micronuclei, suggesting that hypothermia affected the mitotic apparatus. The hypothermic response to chlorpromazine and reserpine was weaker in rats than in mice, and it was correspondingly more difficult to induce micronuclei in rats with those drugs.     

Role of endogenous nitric oxide (NO) and NO synthases in healing of indomethacin-induced intestinal ulcers in rats

We examined the roles of nitric oxide (NO) and NO synthase (NOS) isozymes in the healing of indomethacin-induced small intestinal ulcers in rats. Animals were given indomethacin (10 mg/kg, s.c.) and killed 1, 4 and 7 days after the administration. Indomethacin (2 mg/kg), N(G)-nitro-L-arginine methyl ester (L-NAME: a nonselective NOS inhibitor: 10 mg/kg) and aminoguanine (a relatively selective iNOS inhibitor: 20 mg/kg) were given s.c. once daily for 6 days, the first 3 days or the last 3 days during a 7-day experimental period. Both indomethacin and L-NAME significantly impaired healing of these lesions, irrespective of whether they were given for 6 days, first 3 days or last 3 days. The healing was also impaired by aminoguanine given for the first 3 days but not for the last 3 days. Expression of iNOS mRNA in the intestine was up-regulated after ulceration, persisting for 2 days thereafter, and the Ca(2+)-independent iNOS activity also markedly increased with a peak response during 1-2 days after ulceration. Vascular content in the ulcerated mucosa as measured by carmine incorporation was decreased when the healing was impaired by indomethacin and L-NAME given for either the first or last 3 days as well as aminoguanidine given for the first 3 days. These results suggest that endogenous NO plays a role in healing of intestinal lesions, in addition to prostaglandins, yet the NOS isozyme mainly responsible for NO production differs depending on the stage of healing: iNOS in the early stage and cNOS in the late stage.     

Comparative study on the gastroprotective potential of some antidepressants in indomethacin-induced ulcer in rats

Clinical studies have shown that anxiolytic and antidepressant drug therapy benefits patients with ulcers. Many antidepressant drugs have been shown experimentally to produce antiulcer activity in various ulcer models. This study investigated the antiulcer activities of tianeptine, trazodone, and venlafaxine on indomethacin-induced ulcers in rats; and evaluated tianeptine's effects on oxidant and antioxidant parameters in rat stomach tissue. The results show that trazodone and venlafaxine did not prevent indomethacin-induced ulcers. Tianeptine, however, decreased indomethacin-induced ulcers significantly at all doses used (6, 12, and 25 mg/kg). Famotidine, an H₂ receptor blocker, showed the highest antiulcer activity. Tianeptine significantly prevented the decrease in glutathione (GSH) content that occurred in the indomethacin-only group's damaged stomach tissues. All doses of tianeptine, but especially the 25 mg/kg dose, significantly decreased catalase (CAT) activity in stomach tissue, compared to the control. All doses of tianeptine eliminated the decrease in superoxide dismutase (SOD) activity in the stomach tissue of rats given indomethacin. Although all doses of tianeptine significantly decreased the malondialdehyde (MDA) content, all doses of tianeptine, except 6 mg/kg, decreased myeloperoxidase (MPO) activities significantly compared to the control. Our results indicate that activating enzymatic and non-enzymatic antioxidant mechanisms and inhibiting some toxic oxidant mechanisms play a role in tianeptine's antiulcer effect mechanism.     

Differences in the effects of amphetamine and methylphenidate on brain dopamine turnover and serum prolactin concentration in reserpine-treated rats.

In the present study we compared the ability of amphetamine and methylphenidate to antagonize the elevation of serum prolactin produced by reserpine because of the differences in the actions of amphetamine and methylphenidate on brain dopamine turnover. Groups of male rats were treated with either methylphenidate (10 mg/kg) or amphetamine (5 mg/kg) alone or in combination with reserpine (5 mg/kg). The reserpine treatment was given 4 hours before methylphenidate or amphetamine, and the rats were killed 5 hours after reserpine. Neither amphetamine nor methylphenidate alone was able to suppress serum prolactin. Amphetamine but not methylphenidate was able to block the increase of serum prolactin in response to reserpine. Amphetamine lowered brain DOPAC in control and reserpine-treated rats, but methylphenidate elevated brain DOPAC in control rats and had no effect in reserpine-treated rats. These results indicate that the methylphenidate group of CNS stimulants can be differentiated on the basis of their neuroendocrine effects from the amphetamine group of stimulants.     

Effect of 16,16-dimethyl PGE2 on renal papillary necrosis and gastrointestinal ulcerations (gastric, duodenal, intestinal) produced in rats by mefenamic acid

Mefenamic acid, given orally to rats at a single dose of 1200 mg/kg, produced renal papillary necrosis (RPN) in 63% of animals. The incidence was reduced to 27% by 16,16-dimethyl PGE2 (dmPGE2), given at an oral dose of 0.75 mg/kg t.i.d. RPN is likely to be caused by the renal prostaglandin depletion elicited by mefenamic acid, an inhibitor of prostaglandin cyclooxygenase. Substitution with dmPGE2 reduces RPN presumably by preventing the prostaglandin depletion. We conclude that the prostaglandin used is cytoprotective for the kidney. Mefenamic acid, like most nonsteroidal anti-inflammatory compounds (NOSAC), produced ulcerations of the small intestine (jejunum and ileum). These were prevented by dmPGE2 (intestinal cytoprotection). Unlike most other NOSAC, however, mefenamic acid produced duodenal ulcers in nearly all animals (80%). Of these ulcers, 88% were perforated. Twenty-five of the twenty-six animals that died had a perforated ulcer. These duodenal ulcers were also prevented by dmPGE2. Mefenamic acid-induced ulcers could be used as an experimental model for testing agents with a potential for preventing or healing duodenal ulcers.     

The depletion of the granules of argyrophile cells of dog duodenum by reserpine

Summary The influence of reserpine on the argentaffin and non-argentaffin argyrophile cells of the duodenum has been studied in 8 dogs. In two dogs that were given 5 mg/kg of reserpine there was a complete disappearance of both types of cells. In another dog given 5 mg/kg and in dogs given 2.5 mg/kg and 1 mg/kg reserpine, the number of argentaffin cells was reduced to almost nil while the number of non-argentaffin argyrophile cells showed a statistically significant reduction. The degree of depletion of non-argentaffin argyrophile cells was proportional to the dose of reserpine given. The findings show that the non-argentaffin argyrophile cells are closely related to 5-hydroxytryptamine and their distinction from argentaffin cells is only a quantitative one.     

Evidence for thimerosal induced cytoprotection on rat stomach

Intragastrically administered thimerosal protects against ethanol induced ulceration with an ID50 of 1.6 mg/kg body weight. In contrast, intravenously administered thimerosal exhibits an ID50 of greater than 30 mg/kg. The antiulcerogenic effect of thimerosal persists for at least 20 hours before allowing gastric ulcers to be induced by ethanol. Intragastric application of thimerosal protects against acetyl salicylic acid induced with an ID50 of 6.8 mg/kg. Stress ulceration is inhibited by thimerosal with an ID50 of 9.2 mg/kg body weight. Investigations on the structure-activity relationship show that it is the mercury moiety and not the thiosalicylic acid moiety which is responsible for the inhibition by thimerosal.     

Role of Dopaminergic Mechanisms in the Formation of Stress-Induced Ulcer Damages to the Duodenum and Stomach in Rats

Intraperitoneal injections of 2.5 mg/kg reserpine daily for 3 days combined with immobilization/pain stress evoked the development of ulcerous damages to the duodenum and stomach in rats. This is accompanied by increases in the content of malonic dialdehyde (MDA) and activity of superoxide dismutase (SOD) in erythrocytes, level of vitamin C in the blood plasma, and activity of SOD in a homogenate of the duodenum tissue. Injections of 0.5 mg/kg L-deprenyl (i.p.) and 50 mg/kg pentoxifylline (i.p.) provided protection effects with respect to stress-induced ulcers; the influences of these agents were mutually potentiated.     

Central noradrenergic-cholinergic interaction in regulation of gastric acid secretion in rats

Possible roles of noradrenaline (NA) and acetylcholine (ACh) within the lateral hypothalamic area (LHA) in regulation of gastric acid secretion were examined in urethane anesthetized rats. When NA 30 nmoles was given into the LHA, the gastric acid output decreased and this inhibitory effect of NA was potentiated in rats pretreated with reserpine (2 mg/kg, i.p., 20 hr). Even in a dose of 3 nmoles which was without effect in non-treated control animals, there was a remarkable decrease in acid output. In these reserpinized animals, ACh in a dose of 30 nmoles induced a remarkable increase in acid output, while in the controls this ACh-induced increase was observed only with a 10 times higher dose. In the rats not given reserpine, the cholinergic muscarinic agonist bethanechol (10 nmoles) increased the gastric acid output while nicotine (30 nmoles) was without effect. Therefore, in rats, the central noradrenergic inhibitory mechanisms related to regulation of gastric function may be present at the level of LHA as well as the ala cinerea (area of the dorsal motor nucleus of vagi and the nucleus tractus solitarius). In addition, in the LHA, a cholinergic muscarinic mechanism which elevates gastric acid secretion may be antagonized by a noradrenergic inhibitory mechanism.     

Antioxidant and antiplatelet effects of the alpha-tocopherol-aspirin combination in type 1-like diabetic rats

We analyze the effect of the combination of acetylsalicylic acid (2 mg/kg/day p.o.) and alpha-tocopherol (25 mg/kg/day p.o.) in a type-1-like experimental model of diabetes mellitus on platelet factors, endothelial antithrombotic factors and tissue oxidative stress. In diabetic rats, the combination of drugs had a greater inhibitory effect on platelet aggregation than in untreated control animals with diabetes (88.87%). The combination of drugs had little effect on the inhibition of thromboxane production (-90.81%) in comparison to acetylsalicylic acid alone (-84.66%), potentiated prostacyclin production (+162%) in comparison to alpha-tocopherol alone (+30.55%), and potentiated nitric oxide production (+241%) in comparison to either drug alone (acetylsalicylic acid +125%, alpha-tocopherol +142%). The combination of the two drugs improved the thromboxane/prostacyclin balance (0.145+/-0.009) in comparison to untreated diabetic animals (4.221+/-0.264) and in untreated healthy animals (0.651+/-0.045). It did not potentiate the antioxidant effect of either drug alone, but did increase tissue concentrations of reduced glutathione, especially in vascular tissue (+90.09% in comparison to untreated animals). In conclusion, in the experimental model of diabetes tested here, the combination of acetylsalicylic acid and alpha-tocopherol led to beneficial changes that can help protect tissues from thrombotic and ischemic phenomena.