Effects of aspirin and prostaglandin E2 on interdigestive motility complex and duodenogastric reflux in man

Prostaglandin E2 receptors and their role in gastrointestinal motility - Potential therapeutic targets

Prostaglandin E2 (PGE2) is found throughout the gastrointestinal tract in a diverse variety of functions and roles. The recent discovery of four PGE2 receptor subtypes in intestinal muscle layers as well as in the enteric plexus has led to much interest in the study of their roles in gut motility. Gut dysmotility has been implicated in functional disease processes including irritable bowel syndrome (IBS) and slow transit constipation, and lubiprostone, a PGE2 derivative, has recently been licensed to treat both conditions. The diversity of actions of PGE2 in the intestinal tract is attributed to its differing effects on its downstream receptor types, as well as their varied distribution in the gut, in both health and disease. This review aims to identify the role and distribution of PGE2 receptors in the intestinal tract, and aims to elucidate their distinct role in gut motor function, with a specific focus on functional intestinal pathologies.

Chronic constipation in hemiplegic patients

AIM: To assess the prevalence of bowel dysfunction in hemiplegic patients, and its relationship with the site of neurological lesion, physical immobilization and pharmacotherapy.

METHODS: Ninety consecutive hemiplegic patients and 81 consecutive orthopedic patients were investigated during physical motor rehabilitation in the same period, in the same center and on the same diet. All subjects were interviewed ≥ 3 mo after injury using a questionnaire inquiring about bowel habits before injury and at the time of the interview. Patients’ mobility was evaluated by the Adapted Patient Evaluation Conference System. Drugs considered for the analysis were nitrates, angiogenic converting enzyme (ACE) inhibitors, calcium antagonists, anticoagulants, antithrombotics, antidepressants, anti-epileptics.

RESULTS: Mobility scores were similar in the two groups. De novo constipation (OR = 5.36) was a frequent outcome of the neurological accident. Hemiplegics showed an increased risk of straining at stool (OR: 4.33), reduced call to evacuate (OR: 4.13), sensation of incomplete evacuation (OR: 3.69), use of laxatives (OR: 3.75). Logistic regression model showed that constipation was significantly and independently associated with hemiplegia. A positive association was found between constipation and use of nitrates and antithrombotics in both groups. Constipation was not related to the site of brain injury.

CONCLUSION: Chronic constipation is a possible outcome of cerebrovascular accidents occurring in 30% of neurologically stabilized hemiplegic patients. Its onset after a cerebrovascular accident appears to be independent from the injured brain hemisphere, and unrelated to physical inactivity. Pharmacological treatment with nitrates and antithrombotics may represent an independent risk factor for developing chronic constipation.

Serotonergic and non-serotonergic targets in the pharmacotherapy of visceral hypersensitivity

Visceral hypersensitivity is considered a key mechanism in the pathogenesis of functional gastrointestinal (GI) disorders. Targeting visceral hypersensitivity seems an attractive approach to the development of drugs for functional GI disorders. This review summarizes current knowledge on targets for the treatment of visceral hypersensitivity, and the status of current and future drug and probiotic treatment development, and the role of pharmacogenomic factors.

Maize meal predisposes to endemic squamous cancer of the oesophagus in Africa: breakdown of esterified linoleic acid to the free form in stored meal leads to increased intragastric PGE2 production and a low-acid reflux

Endemic cancer of the oesophagus in Africa is associated with the use of maize as the staple. In one African community endemic cancer of the oesophagus has been shown to have a strong statistical association with the consumption of foods based on maize in the meal form. A strong association with consumption of maize meal has also been shown in a region of Italy. It has been argued in the past that the association with maize consumption is due to a fortuitous association; or due to the nutritional deficiencies of maize meal; or due to fungal contamination. We argue that maize meal is a distinctly different food from whole maize, and that nutritional content as much as deficiency is responsible for predisposition of the oesophagus to carcinogenesis. An important factor is the breakdown of esterified linoleic acid to the free form in stored maize meal. This leads to excess production of prostaglandin E2 in the stomach. The excess Prostaglandin E2 causes a low-acid duodenogastro-oesophageal reflux, which predisposes to carcinogenesis. Supporting evidence is available that the steps of this mechanism occur in endemic areas, and that they are associated with the carcinogenic process. Health measures including poverty alleviation, health education, and monitoring and control of maize meal storage and content may be required to reduce the incidence of this disease in Africa.

Double-blind, placebo-controlled study on effects of diclofenac sodium and indomethacin on postprandial gastric motility in man

Data from animal studies suggest that NSAIDs-induced gastric damage may be due to increased gastric motility. Such a mechanism, however, has never been tested or demonstrated in man. We evaluated the effects of two frequently prescribed NSAIDs, indomethacin and diclofenac sodium, on postprandial gastric motor activity (a physiologically reproducible stimulus) in healthy volunteers to see whether these compounds increase gastric motility. Twenty-four healthy volunteers of both sexes, 21-35 years of age, underwent a basal gastric motility recording. Thereafter, they were randomized in three groups to receive either placebo, indomethacin (50 mg three times a day) or diclofenac sodium (50 mg three times a day) for a week. At the end of the week, they underwent an identical manometric study. Analysis of the motility tracings showed no difference in gastric antral motility index and in amplitude of gastric antral contractions after NSAIDs with respect to the basal study and to the placebo group. About 50% of subjects (two in the placebo group) complained of side effects. These were transient and mild, except in two subjects taking indomethacin, in whom endoscopy was necessary; one of these had a small prepyloric ulcer. It is concluded that in man NSAID-related gastric damage is unlikely to be due to increased gastric motility.

Effects of parenteral diclofenac sodium on upper gastrointestinal motility after food in man

In experimental animal models nonsteroidal anti-inflammatory drugs may influence gastrointestinal motility, but as evidence is lacking in man. The effect of diclofenac sodium 75 mg i.m. on the motor response of the upper gastrointestinal tract to food has been studied by manometry in 9 healthy volunteers. Diclofenac had no effect on the motor activity of the stomach, duodenum, or jejunum after a 605 kcal meal.

Antroduodenal motility studied by real-time ultrasonography. Effect of enprostil

Transabdominal real-time ultrasonography was used to investigate antroduodenal motility effects of the prostaglandin E2 analogue enprostil. Ten healthy subjects were studied on two separate days, once after oral administration of one capsule of enprostil 35 micrograms 1 hour before the ingestion of 500 mL of meat soup and once without drug administration before the meal. The ultrasound probe was positioned at the level of the transpyloric plane to visualize the antrum, pylorus, and proximal duodenum simultaneously and thereafter vertically to visualize the antrum, superior mesenteric vein, and aorta simultaneously. The motility was videotaped for 15 minutes. The antroduodenal coordination, frequency and amplitude of antral contractions, and size of antral area were reduced, whereas the time during which the pylorus was wide open (greater than 5 mm) was increased after enprostil. It is concluded that antroduodenal motility can easily be visualized by ultrasonography. Therapeutic doses of enprostil impair antroduodenal peristalsis and coordination and open the pylorus in healthy subjects.

Misoprostol treatment exacerbates abdominal discomfort in patients with non-ulcer dyspepsia and erosive prepyloric changes. A double-blind, placebo-controlled, multicentre study

One hundred and thirty-seven consecutive outpatients with non-ulcer dyspepsia (NUD) and erosive prepyloric changes (EPC) were randomly allocated to double-blind treatment with 400-micrograms misoprostol tablets twice daily or placebo for 4 weeks. Misoprostol had a significant worsening effect on epigastric pain, nausea, meteorism, lower abdominal pain, and diarrhoea, as compared with placebo. The fact that symptoms in patients with NUD and EPC were exacerbated by an antisecretory dose of misoprostol indicates that the symptoms are largely unrelated to gastric acid.

Oral prostaglandin E analogues induce intestinal migrating motor complexes after a meal in dogs. Evidence for a central mechanism

The effects of oral, intravenous, and intracerebroventricular administration of synthetic derivatives of prostaglandins E1 (misoprostol) and E2 (enprostil) on postprandial gastrointestinal motility were investigated in dogs chronically fitted with strain gauge transducers on the antrum and the proximal and middle jejunum. Synthetic prostaglandin E analogues administered orally at a dose of 20-50 micrograms/kg 15 min before the meal did not modify the postprandial pattern of gastric contractions but suppressed the spontaneous postprandial irregular activity on the jejunum and induced a cyclic pattern of migrating motor complexes for 4-6 h after the meal. These postprandial migrating motor complexes induced by prostaglandin E were propagated between the two recording sites and had a period similar to that observed in the fasted state. However, the duration of phase 2 was significantly increased and the amplitude of the phase 3 decreased. This jejunal cyclic motor pattern was reproduced by administration of synthetic prostaglandin E derivatives either intravenously (4-10 micrograms/kg) 15 min before the meal or intracerebroventricularly (50 ng/kg) 1 h after the meal. The intestinal migrating motor complex activity observed after oral administration of synthetic prostaglandin E derivatives was abolished by the previous intracerebroventricular (40 micrograms/kg) but not intravenous (200 micrograms/kg) administration of SC-19220, a receptor antagonist of prostaglandin E. These results suggest that oral administration of synthetic prostaglandin E1 (misoprostol) or prostaglandin E2 (enprostil) analogues before a meal induces postprandial migrating motor complexes on the jejunum in dogs through a mechanism involving central prostaglandin receptors.

The effect of enprostil on duodeno-jejunal motility in man

Motor changes could be involved in the pathogenesis of diarrhoea that complicates the treatment of ulcer disease by prostaglandins. Our aim was to assess the effect of enprostil, a synthetic analogue of PGE2, on duodeno-jejunal motility. During this randomized double-blind crossover study, two manometric recordings, each lasting 20 h (12.00-08.00 hours), were carried out during dosing with 35 micrograms enprostil b.d. or placebo (eight volunteers: part 1), or during dosing with 35 or 70 micrograms enprostil b.d. (nine volunteers: part 2). Subjects were only allowed a standard dinner at 18.00 hours. During fasting, in part 1, the number of phase 3 activity patterns (PIIIs) was higher with enprostil than with placebo (P less than 0.01), without any difference in their characteristics; the overall duration of phase 1 activity was longer with enprostil than with placebo (P less than 0.01). In part 2, during fasting the number and characteristics of the PIIIs were not different, but there was a dose-related increase in PI, and decrease in PII activity. Fed motor patterns did not differ between the two doses of enprostil.

Cisapride stimulates antral motility and decreases biliary reflux in patients with severe dyspepsia

Duodenogastric reflux has a deleterious effect on the gastric mucosa. It was the aim of this study to assess the acute effects of cisapride on antroduodenal motility and duodenogastric reflux in seven patients with severe dyspepsia and increased biliary reflux, as evidenced by increased bile salt output in their gastric aspirates. Each patient underwent two studies on separate days. On each day, after an overnight fast, each patient swallowed a multilumen tube for manometric recording of gastroduodenal motility. Phenol red was infused into the second portion of the duodenum, gastric juice was aspirated, and motor activity was monitored for 90 min. At the end of this period, the patient received either cisapride or placebo intravenously in a double-blind randomized fashion. Antroduodenal motility and duodenogastric reflux were monitored for the subsequent 90 min. A significantly (P less than 0.01) higher motility index was found in the antrum after cisapride (2678 +/- 712 vs 1110 +/- 412 in the basal period) while placebo had no effect. The duodenal motility index was not affected by cisapride or placebo. Bile salt outputs in gastric aspirates were significantly (P less than 0.05) reduced following cisapride injection (0.42 +/- 0.6 mmol vs 1.6 +/- 1.2 mmol during basal period). Conversely, outputs of phenol red in the gastric aspirates were unaffected by cisapride. In conclusion, cisapride stimulates antral motility and decreases biliary reflux in patients with dyspepsia and increased duodenogastric reflux.

Antroduodenal motility and gastric emptying. Gastroduodenal motility and pH following ingestion of paracetamol

The influence of paracetamol on antroduodenal motility and gastric pH was studied in 11 healthy subjects and the relationship between gastroduodenal motility and gastric emptying rate time, tmax, to peak concentration of serum paracetamol, Cmax, was evaluated. The incidence of antral phase III activity and the duration of phase III was diminished with paracetamol (P less than 0.05). The other motility parameters assessed were unchanged. Three patterns of motility and absorption were observed. One group (n = 5) were fast absorbers with a tmax of 1 h and a motility pattern characterized by antral activity, a high motility index and a short duration of phase II (33-60 min); the phase IIIs were complete except in one case. The second group (n = 4) had tmax at 1.5 h and their phase II motility was characterized by a longer duration (80-133 min) (P less than 0.05), by antral activity, and by a high motility index; their phase IIIs were all incomplete. The last group (n = 2) were slow absorbers: Cmax was not reached in the investigation period, no antral contractions were seen, and the motility index was low. The area under the serum-concentration curve of paracetamol differed between the groups at 90 and 180 min (P less than 0.01).

Mucosal prostaglandin levels of the gastric stump

The endogenous mucosal PG levels (PGE2, PGF2 alpha, PGI2, TXB2) of the gastric stump were investigated from biopsy materials, after partial gastrectomy made for ulcer disease. The mucosa of the stomach remnant were found to contain mainly PGE2 and PGI2. The PG contents of the mucosa of gastric stump were not influenced by the type of resection. Mucosal PG concentrations on the greater curvature were not dependent on the patients' age, the indication of the gastrectomy, the duration of postoperative interval, or the sex of the patient. There was no relation between the secretion capacity of the resected stomach and the mucosal PG contents of the greater curvature. After Billroth I and II gastrectomy procedures equivalently fair correlations have been established between the mucosal levels of PGE2 and PGF2 alpha, PGE2 and TXB2, PGF2 alpha and TXB2, PGI2 and TXB2 on the greater curvature, respectively. After both types of gastrectomy the mean PGI2 mucosal concentration of the greater curvature was significantly lower than those of the gastroenteroanastomosis and lesser curvature below the cardia, which in turn did not differ from each other. Biliary reflux does not cause characteristic alterations of the mucosal PG levels on the greater curvature. No definite relation between the histological findings of the mucosa and the PG concentrations was observed, which suggests a secondary role of the endogenous PGs in the pathogenesis of light microscopic mucosal alterations of the resected stomach.

Effects of prostaglandins E2 and F2 alpha on motility of small intestine in man

Interdigestive motility of the small intestine was examined in 23 fasted healthy volunteers following luminal administration of the prostaglandins E2 and F2 alpha. Motility was monitored by means of water-perfused catheters measuring intraluminal pressure changes. The registration points were located 25 cm apart, in the proximal duodenum, at the angle of Treitz, and in the jejunum. Prostaglandin E2 administered intraduodenally delayed the initiation of the subsequent activity front. The interval to the next activity front was prolonged by a dose of 1.0 mg prostaglandin E2 from 79.5 +/- 9.5 min to 137.1 +/- 5.0 min (P less than 0.01) and to 158.0 +/- 14.0 min by 2.0 mg prostaglandin E2 (P less than 0.05). Also, in four of seven experiments, a progressing activity front was arrested by 2.0 mg prostaglandin E2. Prostaglandin F2 alpha at 2.5 or 5.0 mg given intraduodenally induced bursts of contractions with a frequency of 17.7 +/- 0.8 contractions per minute and an amplitude of 10 to 110 mm Hg (P less than 0.01). In comparison, food intake produced irregular contractions at a frequency of 5.3 +/- 1.8 contractions per minute and an amplitude of 10 to 50 mm Hg (P less than 0.05). It is concluded that prostaglandin E2 delays the initiation of activity fronts in the duodenum. In contrast, prostaglandin F2 alpha changes the interdigestive motility pattern to one of intense contractile activity, which is different from the postprandial motility pattern.

Abnormalities of the migrating motor complex in diabetics with autonomic neuropathy and diarrhea

Diarrhea is a common symptom in long-standing diabetes. The pathogenesis of this diarrhea remains obscure, although it appears to be related to the development of autonomic neuropathy, which may cause several abnormalities including altered gut motility. We studied fasting gastrointestinal motility for a mean of 210 min in a group of 12 type-II diabetics with diarrhea. All patients had peripheral neuropathy and symptoms of autonomic neuropathy. Their motor activity was compared with that of a group of six normal volunteers. In addition, gastrointestinal transit time was assessed by the hydrogen breath test. The presence of bacterial overgrowth was assessed by the hydrogen breath test and culture of jejunal secretions. The diabetics showed grossly disordered motor activity. There was a complete absence of phase-III activity in two patients. Most phase III's commenced in the distal duodenum or jejunum. The phase-III component was often of short duration at each recording site. There was increased velocity of propagation between sites. Continuous phase-II activity was noted in some patients. Antral activity was absent or reduced during phase II. Gastrointestinal transit time was significantly prolonged in the diabetics. Bacterial overgrowth was demonstrated in three diabetic subjects. These motility abnormalities are nonspecific and are unlikely to play a major role in the pathogenesis of diabetic diarrhea.

The influence of variable gastric emptying and intestinal transit rates on the plasma level curve of cimetidine; an explanation for the double peak phenomenon

A physiological flow model is presented to account for plasma level double peaks based on cyclical gastric emptying and intestinal motility in the fasted state. Central to the model is the assumption that gastric emptying and intestinal transit rates will vary directly with the strength of the contractile activity characteristic of the fasted state motility cycle. Simulated curves clearly indicate that variable gastric emptying rates can result in variable absorption rates from the gastrointestinal tract and double peaks in the plasma level curves of cimetidine. Vital to the occurrence of double peaks are (i) dosing time relative to phasic activity, (ii) variability in flow out of the stomach, and (iii) a small emptying rate constant Qs/Vs, for a period of time within the first hour after administration. Variability in intestinal flow rates alone does not cause a double peak in the plasma level curve. Results of the simulations, as well as experimental results, can be categorized according to the shapes of the plasma level curves into four types: type A, Cpmax (1) less than Cpmax (2); type B, single peak; type C, Cpmax (1) greater than Cpmax (2); type D, Cpmax(1) = Cpmax(2). Assuming that the experimental results were obtained from fasted subjects, with the time of dose administration being a random variable, the frequency of the experimental curves having shape A, B, C, or D correlates extremely well with theoretical predictions. It is concluded that variable gastric emptying rates due to the motility cycle can account for plasma level double peaks. Furthermore, variable gastric emptying rates combined with the short plasma elimination half-life and poor gastric absorption of cimetidine can be the cause of the frequently observed plasma level double peaks.

Effect of 15(R),15-methyl prostaglandin E2 and indomethacin on pancreatic secretion in man

In addition to gastric mucosal cytoprotective and antisecretory effects, prostaglandin E2 has a beneficial effect on experimental pancreatitis in some animal models, while prostaglandin synthesis inhibitors such as indomethacin and salicylates may induce pancreatitis at maximal doses. However, their effect on human pancreas is unclear. For this reason we considered it necessary to delineate their actions on human pancreatic secretion. Six healthy volunteers were studied on six separate days. On day 1, against a background of 1 pmol/kg/hr secretin, increasing doses of CCK were infused intravenously. On day 2, increasing doses of an amino acid mixture were infused intraduodenally and both studies were repeated on two occasions, following 100 micrograms 15(R), 15-methyl prostaglandin E2 per os on one and following indomethacin 50 mg orally 12 and 1 hr prior to the study on the other. Both indomethacin and PGE2 had no significant effect on pancreatic secretion in response to graded doses of CCK. 15(R),15-Methyl prostaglandin E2 and indomethacin caused a reduction of amylase output in response to the higher doses of intraduodenal amino acids. The prostaglandin E2 derivative also elicited a significant increase in basal bicarbonate output.

IN CONCLUSION

the acute effects of 15(R),15-methyl prostaglandin E2 and indomethacin on human pancreatic secretion do not seem to offer an explanation for the mechanisms of protection against experimental acute pancreatitis or an association with pancreatitis, respectively.