Time course study on the action of 5-hydroxytryptamine on gastric secretion and mucosal blood flow and on ethanol-induced gastric mucosal damage in rats

The effects of 5-hydroxytryptamine (5-HT; given i.p. in doses of 1 or 10 mg/kg) on gastric secretion and mucosal blood flow (GMBF) and on ethanol-induced gastric mucosal damage were studied in rats over a period of 30-450 min. The blood pressure was also examined, in relation to the changes in GMBF. 5-HT, 10 mg/kg, given 30 min before ethanol administration markedly worsened lesion formation and this potentiating action was present for a further 90 min; a significant protective effect was seen only at 450 min after 5-HT injection. The lower dose of 5-HT, 1 mg/kg, did not affect the severity of gastric damage. 5-HT (10 mg/kg) also decreased GMBF at 30 min after injection and this lasted up to the end of 120 min, but the depressive action of ethanol on GMBF was reversed at 450 min. The basal gastric secretory volume was depressed from 30 to 120 min but acid output fell from 75 to 120 min after the higher dose of 5-HT; this reduction of acid secretion was followed by an increase from 360 to 450 min. 5-HT decreased the mean blood pressure in a dose- and time-dependent manner. The heart rate was unaffected by either dose level of 5-HT. The present study not only demonstrates the ulcerogenic action of 5-HT but also the protective nature of the amine. The reduction in secretory volume and lesion formation, but not acid secretion, seems to be related to GMBF depression, whereas the protective action depends on the maintenance of GMBF.

Ethacrynic acid and sulphasalazine inhibit the generation of leukotriene C4 in rat stomachs: a possible gastric anti-ulcer mechanism in cold-restraint-stressed rats

The role of gastric glandular mucosal leukotriene C4 in gastric ulceration, produced by restraint at 4 degrees C (stress) for 2 h in rats, was studied in relation to the ulcer-preventing effects of ethacrynic acid, sulphasalazine and its constituents (sulphapyridine and 5-aminosalicylic acid), AA-861 and ONO-1078. Stress itself significantly raised mucosal leukotriene C4 levels; pretreatment with ethacrynic acid, sulphasalazine, sulphapyridine or AA-861 antagonised these changes and reduced the severity of gastric ulceration. Mucosal mast cell degranulation was prevented by ethacrynic acid, sulphasalazine, 5-aminosalicylic acid, AA-861 or ONO-1078; the mucus-depleting effect of stress was also reversed by all these drugs, except for 5-aminosalicylic acid. The anti-ulcer effect of ethacrynic acid and sulphasalazine appears to be related to their influence on glandular mucosal leukotriene C4 levels.

The pharmacological differences and similarities between stress- and ethanol-induced gastric mucosal damage

Stress- and ethanol-induced gastric mucosal damage are the two commonly used ulcer models in animals. They share some of the similarities but also have differences in the etiology of gastric ulceration. This article reviews the influences of various protective drugs on these two types of gastric damage in rats. Verapamil (a calcium antagonist) or N-ethylmaleimide (a sulfhydryl depletor) prevents cold restraint-, but potentiates ethanol-provoked gastric lesion formation. N-Acetylcysteine (a mucolytic agent) and acetaminophen (an antipyretic analgesic) have the opposite actions. Prostaglandins provide a much better antiulcer effect on ethanol-induced lesions. Cimetidine (a histamine H2-receptor antagonist) prevents only stress-induced mucosal damage. These differences in drug actions indicate that stress and ethanol may have dissimilar ulcerogenic mechanisms in rats. On the other hand, carbenoxolone (a mucus inducer), histamine H1-receptor antagonists, leukotriene inhibitors (FPL 55712 and nordihydroguaiaretic acid) and mast cell stabilizers (like zinc compounds, sodium cromoglycate, FPL 52694 and ketotifen), all protect against gastric mucosal damage by stress or ethanol in rats. However, the role of gastric sulfhydryls in both types of gastric lesions is still controversial. These findings imply that the two types of lesion formation share some of the ulcerogenic mechanisms. This communication attempts to analyze the various findings and to relate them to the etiology of stress and ethanol-induced gastric lesions. It also summarizes the uses, and the antiulcer mechanisms, of the drugs that have been studied utilizing these two animal ulcer models, and suggests their possible implications in man.

The role of the gastric mucosal sulfhydryls in the ulcer-protecting effects of sulphasalazine

The role of gastric mucosal sulfhydryls in gastric ulceration, produced by restraint at 4 degrees C (stress) for 2 h, and in the ulcer-protecting effects of sulphasalazine and its constituents (sulphapyridine and 5-aminosalicylic acid), have been studied in rats. Stress significantly raised the mucosal sulphydryl content, but sulphasalazine and sulphapyridine did not influence these changes; only 5-aminosalicylic acid decreased the mucosal sulphydryl concentration. These results indicate that depletion of mucosal sulfhydryls does not occur in stress-induced ulceration, in contrast to what has been shown in other experimental ulcer models. The antiulcer effects of sulphasalazine or of any of its constituents may, therefore, not involve the sulphydryl mechanism.

Effects of adenosine on gastric and cardiovascular systems, and ethanol ulceration in male and female rats

The time course of the effects of adenosine, a vasodilator, on the ulcerogenicity of ethanol was studied in male and female rats. Gastric secretory function and mucosal blood flow (GMBF), systemic blood pressure and heart rate were monitored during the 90-min experimental period. In the male rats, adenosine 7.5 mg/kg s.c. (injected at 30 min) increased the GMBF at 45 min and depressed it at 75 min. The mean blood pressure was decreased at 45 min and steadily recovered thereafter; the heart rate was unaffected throughout the experimental period. The gastric secretory volume was elevated at 60 min, with a significant drop in gastric acid output at the same time. Ethanol administration from 45 to 90 min produced haemorrhagic lesions in the glandular mucosa. The severity of gastric damage was markedly reduced by adenosine at 45 and 60 min when the GMBF and the secretory volume were increased respectively, but severity was increased at 75 min while the GMBF was significantly reduced. In the female rats, adenosine had no effect on the secretory function but still had a depressive action on GMBF at the 75th min. In these animals, adenosine exacerbated the gastric injury at 60 and 75 min. The blood pressure was also decreased at 45 min. In conclusion, adenosine produces a different pattern of effects on the ulcerogenic action of ethanol in male and in female rats. These differential effects depend on the states of GMBF and gastric secretory volume but not on the changes of systemic blood pressure and gastric acid secretion.

In vitro study of ethanol on the electrical parameters in rat stomachs

The electrophysiological effects of mucosal or submucosal ethanol (5, 10, or 20%) were assessed in isolated stomach preparation. Mucosal incubation with these concentrations of ethanol dose- and time-dependently decreased the transmucosal potential difference (PD), while the electrical current (I) and resistance (R) were unaffected. Submucosal exposure to the same concentrations of ethanol also reduced the PD, but to a lesser extent; only 20% of ethanol produced a significant effect. This same dose of ethanol not only decreased I but also increased R to a significant level. These findings indicate that transmucosal PD appears to be generated largely by the mucosal epithelial cell barrier, while the I and R are elicited by the laminea propria mucosa which is easily approached and altered by ethanol which acts from the submucosal side. The significance of the effects produced by mucosal or submucosal ethanol is discussed.

Ulcerogenic mechanism of ethanol and the action of sulphanilyl fluoride on the rat stomach in-vivo

The effects of ethanol alone and in combination with sulphanilyl fluoride on some of the antioxidant defences in the stomach of rats have been examined. These effects were correlated with lesion formation in the gastric mucosa. Oral administration of ethanol induced gastric lesions which were prevented by sulphanilyl fluoride pre-treatment. N-Ethylmaleimide antagonized the anti-lesion action of sulphanilyl fluoride. Ethanol administration lowered the glucose-6-phosphate dehydrogenase activity in the gastric mucosa, an effect potentiated by N-ethylmaleimide pre-treatment. The total superoxide dismutase activity was unaffected by the drugs used in the present study. Ethanol, however, markedly increased mucosal catalase activity which was reduced by sulphanilyl fluoride pretreatment and reversed by N-ethylmaleimide. It is concluded that the ulcerogenic mechanism of ethanol is mediated at least in part by the depression of the hexose monophosphate shunt and the production of active oxygen species, whereas the anti-lesion action of sulphanilyl fluoride is probably not mediated through these mechanisms.

Chronic nicotine treatment intensifies gastric ulceration by cold-restraint stress in rats

Nicotine 5, 25 or 50 micrograms/ml drinking water given ad lib for 5, 10 or 20 days, dose- and time-dependently worsened cold-restraint-induced (stress) ulceration in rat stomachs. Treatment with nicotine 5 or 25 micrograms/ml did not influence the number of gastric mucosal mast cells degranulated by cold and restraint; however, drinking 50 micrograms/ml for 10 days lowered further the mast cell count in stressed animals. During 20-day nicotine administration, the daily food intake and body weight gain, up to the 18th day when the animals were starved before experiments, were not affected by the three concentrations of the alkaloid, except that fluid consumption tended to be less only in those animals given the highest dose. The findings indicate that chronic nicotine treatment exacerbates the severity of stress-evoked ulcer formation. The ulcer-intensifying mechanism of the two lower doses of nicotine appears not to be related to additional mast cell degranulation; only the ulcerogenic action of the highest concentration includes this factor. It is unlikely that ulcer aggravation by nicotine is due to malnutrition because body weight gain and solid food intake by the alkaloid-treated rats were normal.

[The identification of high-risk pregnancy, using a simplified antepartum risk-scoring system]

This study was carried out to assess the problems with the pregnant women, and check out the risk-factors in the high-risk pregnancies, using a simplified antepartum risk-scoring system, which was revised from Edwards' scoring system to be suitable for Korean situation. This instrument was included 4 categories, demographic, obstetric, medical and miscellaneous factors. This survey was based on the 1300 pregnant women who were admitted, from Jan. 1, 1988, to May 31, 1990, Chung Ang Medical Center. Data were collected from June 25, 1990 to July 7, 1990. Data was analyzed by x2-test, F-test, Pearsons correction, using statistical package SAS in NAS computer system, KIST. The results of the study were as follows; 1. 1313 infants were deliveried of these 560 infants (42.7%) were born to mothers with risk-scores greater than 7, and 753 infants (57.3%) were born to mothers risk-scores less than 7. 2. Maternal age, parity, education level, of the demographic factors were significant relation statistically to identify the high risk pregnancies (X2 = 20.88, 42.87, 15.60 P less than 0.01). 3. C-section, post term, incompetent cervix, uterine anomaly, polyhydramnios, congenital anomaly, sensitized RH negative, abortion, preeclampsia, excessive size infant, premature, low birth weight infant, abnormal presentation, perinatal loss, multiple pregnancy, of the obstetric factors were significant relation statistically to identify the high risk-pregnancies. (chi 2 = 175.96, 87.5, 16.28, 21.78, 9.46, 8.10, 6.75, 22.9, 64.84, 6.93, 361.43, 185.55, 78.65, 45.52, P less than 0.01). 4. Abnormal nutrition, anemia, UTI, other medical condition (pulmonary disease, severe influenza), heart disease, V.D., of the miscellaneous and medical factors, were significant relation statistically to identify the high risk-pregnancies. 5. Premature, low birth weight infant, contracted pelvis, abnormal presentation, of the risk factors were significantly related with Apgar score at 1 & 5 minute after birth and neonatal body weight. 6. Apgar score at 1 & 5 minute after birth and neonatal body weight were significantly negative correlated with risk-score. 7. There were statistically significant difference between risk-score and Apgar score at 1 & 5 minute after birth, 3 group (0-3, 4-6, above 7), and neonatal body weight, 2 group (below 2.5 kg, the other group) (F = 104.65, 96.61, 284.92, P less than 0.01). 8. Apgar score at 1 & 5 minute after birth (below 7), and neonatal body weight (below 2.5 kg), were significant relation statistically with risk score. (chi 2 = 65.99, 60.88, 177.07, P less than 0.01) were 60.8%, 60%.(ABSTRACT TRUNCATED AT 400 WORDS)

The inhibitory action of zinc sulphate on the contractile activity of guinea-pig ileum

The present study examines the inhibitory action of zinc sulphate (ZnSO4) on the contractile response of various agonists on guinea-pig isolated ileum. Different doses of agonists were selected to produce similar contractile activity, in order to compare the degree of inhibition produced by ZnSO4. Preincubation of ileum with ZnSO4 1 x 10(-3) or 3 x 10(-3) M for 10 min dose-dependently and significantly prevented the contraction induced by acetylcholine (1.7 x 10(-8) M), 5-HT (2.4 x 10(-6) M), histamine (5.4 x 10(-7) M) and nicotine (1.7 x 10(-6) M) but not by prostaglandin E2 (PGE2, 8.5 x 10(-9) M). The same doses of ZnSO4 reduced the twitch contraction produced by electrical field stimulation. These findings indicate that the contractile activity of PGE2 is mediated by a mechanism different from that of other agonists and of electrical field stimulation. It is likely that the contractile activity of PGE2 is acting through the receptors on the ileal muscle which are not blocked by ZnSO4 pretreatment.

Nicotine induced gastric injury. A quantitative macroscopic and microscopic analysis of the protective effects of sucralfate and feeding

Nicotine, while an important component of cigarettes, does not cause gross gastric mucosal damage, although its microscopic effect remains unknown. We have evaluated the histology and the microvascular permeability of (a) the effect of nicotine alone or in combination with ethanol on the gastric mucosa of rats and (b) the effect of feeding and sucralfate on the mucosa of rats treated with nicotine and ethanol. Mucosal injury was assessed histologically by the depth of injury and microvascular permeability by the leakage of fluorescein isothiocyanate-labelled albumin. Our results show that nicotine induced microscopic mucosal damage and accentuated the damage induced by alcohol. The damaging effects on mucosa of nicotine and ethanol, alone or in combination, were reduced by pretreatment with sucralfate. Similarly, feeding reduced the degree of mucosal injury. Nicotine and ethanol increased leakage of albumin into the interstitium and the leakage was reduced after sucralfate pretreatment. This study substantiates the adverse effect of smoking on mucosal damage. Vascular factors are probably involved in the pathogenesis.

[The meaning of pain in labor]

From of old, labor has been accompanied by pain and much effort has been made to eliminate or diminish the amounts of pain during labor. Little concern has yet been given to the subjective meaning of pain in labor. Recently, rates of cesarean section in Korea and in some other nations have increased rapidly and some investigators are reporting negative reactions such as anger, disappointment and feeling of loss due to lack of control over labor and its pain. These findings are thought to suggest that control of labor and its pain gives some meaning to the laboring woman. Thus the investigators sought to discover the meaning of pain during labor for Korean women. Specific objectives of this study were to explore the meaning of pain in labor to the mothers, their reactions to the experience of labor and their preference for delivery method. The subjects of this study were 95 mothers who delivered their babies in hospital from September 1989 to May 1990: 45 gave birth by vaginal delivery, and 50 by cesarean section. Data were gathered through direct interviews by the investigators, and questions were focused on five areas i.e. mothers' feelings about delivery and their babies, their feelings about of having more children, the most difficult aspect about this labor and delivery, and what they thought the differences were between vaginal delivery and cesarean section. After interview, mothers' answers were summarized, and classified according to the degree of positive or negative attitude.(ABSTRACT TRUNCATED AT 250 WORDS)

N-ethylmaleimide antagonizes stress-induced gastric ulcers in rats

N-ethylmaleimide (NEM) 10 or 25 mg/kg b.wt, given s.c. 20 min beforehand, dose-dependently and significantly antagonizes the severity of gastric glandular ulcers produced by restraint at 4 degrees C (stress) for 2 h. These findings suggest that reduced activity of endogenous nonprotein sulfhydryl substances in gastric tissue does not worsen stress-induced ulceration in rat stomachs, unlike the deleterious effect its depletion is claimed to have on ethanol-evoked gastric mucosal damage. Thus, decreased SH activity appears not to play a role in the aetiology of mucosal ulcers due to stress.

Calcium and ethanol-induced gastric mucosal damage in rats

The effects of graded doses of ethanol on stomach mucosal damage and calcium levels were studied in rats. The influence of verapamil and/or calcium chloride on these changes was also investigated. Orally administered ethanol (20, 50 or 80% v/v) markedly decreased gastric glandular tissue calcium and it concentration dependently produced mucosal lesions. Pretreatment with verapamil (2.5 or 5 mg/kg, i.p.) dose dependently lessened glandular wall calcium levels and worsened ethanol-induced mucosal damage. Calcium chloride (50 mg/kg, i.p.) significantly prevented ethanol-induced gastric calcium depletion; it also dose dependently antagonized the damaging effect of ethanol as well as the lesion-intensifying action of verapamil. The findings that verapamil potentiated, whereas calcium chloride prevented, ethanol-induced glandular mucosal damage and tissue calcium changes indeed suggest that altered gastric cell calcium levels could be closely related to the mucosal lesions produced by ethanol in rats.

Cholinoceptor blockers protect against ethanol-induced gastric mucosal damage in rats

The role of the cholinergic nervous system in ethanol-induced gastric mucosal damage has been examined in rats. Oral administration of 50 or 80% ethanol produced haemorrhagic lesions which were reduced by atropine pretreatment (0.65, 2.5, 5 or 10 mg/kg injected i.p.); there was lesser protection against the higher dose of ethanol. Pirenzepine (a specific M1 receptor antagonist) pretreatment (0.1, 0.2, 1 or 2 mg/kg, injected s.c.) also protected against ethanol-induced gastric injury to a similar extent; it also increased the amount of adherent mucus on the glandular mucosa. This action may, therefore, account for the protective action of the ganglion blocker. It is concluded that ethanol may stimulate the stomach wall ganglionic nicotinic receptors to activate the postganglionic fibres and subsequently the muscarinic receptors which would then trigger off some of the ulcerogenic mechanisms in the stomach. However, ethanol could also produce gastric damage via the non-cholinergic mechanisms; this action becomes more prominent in gastric injury produced by high doses of ethanol.

The membrane-stabilizing action of zinc carnosine (Z-103) in stress-induced gastric ulceration in rats

Zinc compounds have been shown to antagonize various types of gastric ulceration in rats. Zinc carnosine (Z-103), a newly developed agent was, therefore, examined for its antiulcer effect in stress-induced ulceration and also its membrane stabilizing action in rat stomachs. Cold-restraint (restrained at 4 degrees C for 2 h) stress induced severe hemorrhagic lesions together with increased mast cell degranulation and beta-glucuronidase release in the gastric glandular mucosa. Z-103 pretreatment with a single oral dose (3, 10 or 30 mg/kg) reversed these actions in a dose-dependent manner. When the compound was incubated in concentrations of 10(-7, 10(-6), 10(-5) or 10(-4) M, with isolated hepatic lysosomes, it significantly reduced the spontaneous release of beta-glucuronidase in the medium. The present study not only demonstrates the antiulcer effect of Z-103 but also indicates that the protective action is likely to be mediated by its membrane-stabilizing action on mast cells and lysosomes in the gastric glandular mucosa.

Role of gastric mucosal blood flow in cytoprotection

We compared the effects of graded doses of misoprostol (50-200 mg), omeprazole (12.5-50 mg), cimetidine (6.25-50 mg) and sucralfate (50-200 mg) on gastric mucosal blood flow as measured by laser Doppler flowmetry and gastric mucosal injury induced by ethanol. The results demonstrated that sucralfate, misoprostol and omeprazole, but not cimetidine, increased gastric mucosal blood flow in a dose-dependent manner and protected the mucosa against ethanol damage. The peak and summation blood flow were significantly greater with sucralfate than with misoprostol and omeprazole, but the degree of mucosal protection was similar. These results indicate that the increase in gastric mucosal blood flow, an action which is common to the three drugs, plays an important role in gastric mucosal protection, but other factors are also involved.

Modulatory action of adenosine on gastric function and ethanol-induced mucosal damage in rats

This study examines the gastric effects of adenosine and its antagonist, theophylline, on secretory function, mucosal blood flow, and on ethanol-induced glandular mucosal damage in rats that were fasted for 24 hr before experimentation. The animals were anesthetized with sodium pentobarbitone (50 mg/kg intraperitoneal) and their tracheae cannulated. An ex vivo stomach chamber then was prepared. The luminal bathing solution was collected every 15 min and the concentrations of H+ and Na+ were determined by a pH autotitrator and an ionmeter, respectively. The glandular mucosal blood flow was measured by a laser Doppler flowmeter and the severity of lesions was determined by measuring the hemorrhagic areas. Adenosine administration (2.5 or 7.5 mg/kg, subcutaneous) markedly lowered the H+ and Na+ output but increased the secretory volume and mucosal blood flow in a dose-dependent manner. The same doses of the nucleoside also prevented ethanol-induced mucosal damage. These effects were prevented by pretreatment with theophylline (30 or 60 mg/kg, subcutaneous). Ethanol given alone significantly depressed the H+ and Na+ secretion. Both effects were not modified by adenosine treatment. However, the depressive action of ethanol on mucosal blood flow was prevented by adenosine. These findings indicate that adenosine modulates the physiological function of the stomach. It also directly activates the defensive mechanism of the stomach, which is partially mediated by the improvement of the gastric mucosal blood flow and an increase in the nonacid component of gastric secretion.

The effect of misoprostol, omeprazole and sucralfate on nicotine- and ethanol-induced gastric injury and gastric mucosal blood flow: a comparative study

Nicotine, which is thought to be responsible for part of the pharmacological effect of smoking, exacerbates gastric mucosal injury in rats. The effects of misoprostol (12.5 micrograms to 100 micrograms), omeprazole (12.5 mg to 100 mg) and sucralfate (50 to 400 mg) on gastric mucosal blood flow and mucosal injury induced by nicotine were studied in an ex vivo gastric chamber preparation in rats. Rats were pretreated with nicotine (25 micrograms/mL orally) for 10 days and ethanol was added to the gastric chamber preparation. Laser Doppler flowmetry was used to measure the gastric mucosal blood flow and mucosal damage (ulcer index) was assessed by the area of haemorrhagic lesions. The ulcer index was significantly higher in rats pretreated with nicotine. Treatment with misoprostol and omeprazole lowered the ulcer index significantly compared with controls. The peak and summation blood flows were lower in nicotine-treated rats but failed to reach statistical significance. The peak blood flow (blood flow at 45 min) and the summation blood flow were significantly higher with all doses of sucralfate, misoprostol and omeprazole than in controls (P less than 0.05). The increase in gastric mucosal blood flow was significantly higher with sucralfate and misoprostol than with omeprazole. We conclude that sucralfate, misoprostol and omeprazole prevent nicotine- and ethanol-induced gastric mucosal damage and are accompanied by an increase in gastric mucosal blood flow. This indicates that smoking exacerbates gastric mucosal injury and that cytoprotective and site-protective agents can reduce injury by these noxious agents.

Endogenous prostaglandins: its role in gastric mucosal blood flow and ethanol ulceration in rats

The involvement of endogenous prostaglandins (PGs) in modulating gastric mucosal blood flow (GMBF) is still unclear. The present study was designed to demonstrate the role of this autacoid in the basal GMBF and the restoration of blood flow after restriction of blood supply to the stomach. The ex-vivo gastric chamber was prepared and the GMBF was measured by a laser Doppler technique. 20% ethanol incubation for 10 min in the chamber increased the basal GMBF and lessened the reduction of blood flow induced by absolute ethanol. It also decreased lesion formation caused by ethanol. Indomethacin 5 mg/kg, given s.c 60 min before experimentation had the opposite effects. Ligation of the gastric artery for 20 min which reduced the GMBF by 60%, worsened ethanol ulceration. There was a marked rebound of the GMBF after the ligation was released. Indomethacin totally abolished the blood flow rebound and aggravated ethanol ulceration. However, 20% ethanol incubation significantly potentiated such a rebound in blood flow and reduced lesion formation. Indomethacin pretreatment reversed these actions, whereas misoprostol administration produced the similar effects as 20% ethanol. It is concluded that GMBF plays an important role in ethanol ulceration and both basal and rebound GMBF is probably modulated by endogenous PGs.

Dissociation between the renal and blood acid-base actions of acetazolamide in restraint-stressed rats

Subcutaneous injection of acetazolamide (50 or 200 mg/kg) markedly increased the blood H+ and lowered the HCO3- concentrations in a dose-related manner. The urinary pH and HCO3- excretion were elevated. Restraint stress normalized the blood HCO3- levels but not the H+ concentrations; the high levels of urinary pH and the HCO3- content were unaffected in the acetazolamide-treated animals. These findings suggest that acetazolamide induces metabolic acidosis which appears not to be caused by depletion of blood HCO3- through increased urinary HCO3- excretion. Instead, an extra-renal mechanism could be responsible for the increased blood H+ concentration. Restraint stress significantly decreased the respiratory rate, which was prevented by acetazolamide pretreatment. The reversal of restraint-stress-induced respiratory depression by acetazolamide is probably due to the activation of both peripheral and medullary chemoreceptor sites by acidosis.

Paracetamol potentiates stress-induced gastric ulceration in rats

The effect of paracetamol on gastric ulcers produced by restraint at 4 degrees C for 2 h (stress) was studied in rats. Paracetamol treatment s.c. or p.o., with a dose as high as 250 mg kg-1, did not produce any haemorrhagic lesions in the glandular mucosa. Oral administration with 250 mg kg-1, however, significantly reduced the mast cell count in the gastric glandular mucosa and potentiated haemorrhagic ulceration but not mast cell degranulation caused by stress. The potentiating action was maximum when paracetamol was given between 15 and 30 min before stress. Ranitidine, astemizole, dimethylsulphoxide, sucralfate and verapamil did not protect against the adverse action of paracetamol on stress-evoked lesions. This study suggests that paracetamol worsens stress-induced stomach ulceration by an action which appears not to be due to histamine release, free radical production or intracellular calcium disturbance in the gastric mucosa.

The interaction of ethanol and zinc on hepatic glutathione and glutathione transferase activity in mice

The effects of ethanol and/or zinc sulphate on liver glutathione and glutathione transferase activity were studied in mice. Ethanol suppressed glutathione transferase activity and had no significant effect on glutathione levels in the organ. Zinc sulphate administration dose-dependently increased glutathione transferase activity but did not affect hepatic glutathione content. Furthermore, the depressive action of ethanol on glutathione transferase activity was prevented by zinc sulphate pretreatment. It is suggested that zinc sulphate can reactivate glutathione transferase which in turn increases the excretion of the active metabolites produced by ethanol, through conjugation with glutathione in the liver. This action of zinc may alleviate the hepatic toxicity of ethanol in mice.

The role of serotonin in ethanol-induced gastric glandular damage in rats

The effects of serotonin (5-HT) or methysergide (a 5-HT antagonist), given intraperitoneally 30 min beforehand, on ethanol-induced mucosal injury and mucosal blood flow were studied in rats. 5-HT itself dose dependently decreased the gastric mucosal mucus content and induced gastric damage in conscious animals. It also worsened ethanol-induced lesion formation but not mucus depletion. Methysergide pretreatment only prevented the former action. In the ex vivo chamber preparation, 5-HT lowered the gastric mucosal blood flow and produced mucosal damage in unconscious animals. It also potentiated ethanol-induced gastric injury and 5-HT release. Methysergide significantly prevented lesion formation and 5-HT release in ethanol-treated rats. Ethanol decreased the gastric mucosal blood flow in the mucosa which had been preincubated with HCl. This depression of gastric mucosal blood flow was further reduced by 5-HT, but was reversed by methysergide. The lesion-potentiating or -protecting actions of 5-HT or methysergide, respectively, suggest that the amine is involved in gastric mucosal damage by ethanol in rats.