Effect of prostaglandin 15 (R) 15 methyl-E2-methyl ester on the gastric mucosa in patients with peptic ulceration--an endoscopic and histological study

Aspirin-like drugs cause gastrointestinal injuries by metallic cation chelation

Aspirin-like (nonsteroidal anti-inflammatory) drugs may cause injuries including ulcers to the gastrointestinal tract by chelation of the divalent and/or multivalent metallic cations in the gastrointestinal mucus and mucosa, as suggested by the chemical properties of these drugs and supported by experimental and clinical data.

Effect of 16,16-dimethyl prostaglandin E2 on lipidic organelles of rat gastric surface mucous cells

BACKGROUND

We examined the effect of 16,16-dimethyl prostaglandin E2 (dmPGE2) on the subcellular distribution of phospholipids in rat gastric surface mucous cells (SMCs) using the cytochemical stain, iodoplatinate (IP).

METHODS

The volume of a number of subcellular organelles and the density of IP reactivity within these organelles was determined by modified vertical section stereology.

RESULTS

The volume occupied by most of the subcellular organelles was not affected by dmPGE2 treatment, with the exception that the volume fraction of two classes of large infranuclear inclusion bodies (LIIB1 and LIIB2, organelles we have previously shown to contain hydrophobic lipids), were significantly expanded by a factor of 3-4-fold. The distribution of IP reactivity among the various subcellular compartments appeared to undergo a shift in response to dmPGE2 treatment. Once again the major prostanoid effect was seen in the infranuclear inclusion bodies, as the volume density of IP reactivity was increased 2-24-fold in LIIB1 and 9-10-fold in LIIB2 in comparison to control values.

CONCLUSION

dmPGE2 administration to rats induces an increase in the volume and IP reactivity of a family of lipid-containing organelles, which may underlie its ability to increase the hydrophobic surface properties of the stomach.

Mechanism of inhibitory action of prostaglandins on the growth of human gastric carcinoma cell line KATO III

Prostaglandins (PGs) play important roles in the regulation of various gastric functions. In this study, the effects of various PGs on the growth of the human gastric carcinoma cell line KATO III were investigated. All the PGs tested inhibited KATO III cell growth with a relative potency order of PGE2 greater than PGE1 greater than 17S,20-dimethyl-6-oxo PGE1-methyl ester (ornoprostil) greater than PGF2 alpha. This inhibition was accompanied by an increase of cyclic adenosine monophosphate production. Furthermore, in the presence of guanosine triphosphate, these PGs stimulated adenylate cyclase activity in the plasma membrane of KATO III cells, followed by enhancement of membrane guanosine triphosphatase activity. The relative potencies of these PGs for increasing cyclic adenosine monophosphate levels, activating adenylate cyclase, and enhancing guanosine triphosphatase activity were all comparable to those for inhibiting cell growth. On the other hand, the proliferation of KATO III cells was also inhibited by forskolin as well as dibutyryl cyclic adenosine monophosphate, whereas none of the agents that did not increase cyclic adenosine monophosphate levels had any effect. These results suggest that PGs inhibit KATO III cell growth by stimulating cyclic adenosine monophosphate production via a guanosine triphosphate-dependent process, suggesting the involvement of guanosine triphosphate-binding stimulatory protein, probably coupled to PGE2 receptors, in the action of PGs.

The effects of enprostil and RS-86505-007 on in-vitro intestinal permeability of rabbit and monkey

Enprostil is a prostaglandin E2 analogue characterized as a racemic mixture of four stereoisomers. Enprostil and a single isomer, RS-86505-007, were evaluated for their effects on the permeability of actively and passively transported compounds in segments of small intestine from rabbits and monkeys. Consistent with human in-vivo studies, which have demonstrated decreases in absorption of D-xylose, both compounds inhibited D-glucose transport. The passively transported compounds mannitol and progesterone were also less permeable in this model in the presence of enprostil or RS-86505-007. In contrast to the concentration-dependent inhibition displayed by ouabain, RS-86505-007 had no effect on purified Na+K(+)-ATPase. It is suggested that an effect of a general nature, possibly an increase in the barrier properties at the intestinal surface, may explain the transport inhibition. Of two other enprostil isomers, RS-86812-007 inhibited D-glucose transport in rabbit small intestine, while RS-86505-008 had no effect. The prostaglandin E1 analogue misoprostol was ineffective in monkey and poorly effective in rabbit. This suggests that the inhibition of D-glucose transport by enprostil and its active stereoisomers is mediated through some structurally specific receptor interaction.

Prostaglandins in the gut and their relationship to non-steroidal anti-inflammatory drugs

Prostaglandins are long-chain, saturated, oxygenated fatty acids. Relatively large quantities of prostaglandins have been found in gut mucosa, suggesting that these substances play an important role in gastrointestinal physiology. Non-steroidal anti-inflammatory drugs (NSAIDs) cause damage to the gastric, intestinal, and colonic mucosa in experimental animals and in humans. Prostaglandins protect the gastric mucosa against injury induced by NSAIDs, and this property has been labelled cytoprotection. The mechanisms of cytoprotection have been extensively evaluated and are probably multifactorial, including effects on the gastric mucosal barrier, gastric blood flow, mucus, bicarbonate, and fluid section, ionic transport, cyclic AMP, and surface-active phospholipids. Prostaglandins may also prevent NSAID-induced injury in the small intestine and colon. The mechanisms responsible for prostaglandin protection in the lower gut against injurious agents are unknown. Further studies of the role of prostaglandins in the gut and their relationship to the effects of NSAIDs are needed. The results of these investigations may lead to a better understanding of the importance of prostaglandins in the physiology of the gastrointestinal tract, and may provide information regarding actions of NSAIDs on the functional integrity of the gastric, intestinal, and colonic mucosa.

Effects of secretin on content of PGE2 and 6-keto PGF1 alpha in gastric mucosa

To determine the involvement of prostaglandins in the action of secretin on the promotion of the healing process in injured gastric mucosa, the effect of secretin infusion on the content of PGE2 and 6-keto PGF1 alpha (a major metabolite of PGI2) in human gastric mucosa was investigated. Specimens of both normal and injured mucosa were obtained from each of the patients who underwent polypectomy a week prior to the study. The specimens were obtained before and 20 min after intravenous infusion of secretin [2 Crick, Harper and Raper (CHR) units/kg] or saline. The basal content of PGE2 in injured mucosa was three times higher than that in normal gastric mucosa. Secretin did not increase the PGE2 content of normal gastric mucosa. However, secretin induced a sevenfold increase in the PGE2 content of injured mucosa. The content of 6-keto PGF1 alpha was not affected by secretin. These results suggest that, in injured mucosa, PGE2 is involved in the healing process and in the action of secretin as well.

Stimulatory effect of enprostil, an anti-ulcer prostaglandin, on gastric mucus secretion

Enprostil, a synthetic analogue of prostaglandin E2, is known to be a potent inhibitor of gastric acid secretion, and has marked anti-ulcer activity in rodents. Enprostil was administered in doses ranging from 15 to 250 micrograms/kg to rats prepared using the Shay procedure. Three hours later, the rats' stomachs were removed and processed either for the chemical determination of mucus, or for scanning electron microscopy. For the chemical determination, the secreted gastric juice was removed and the adherent gastric mucus was eluted with 2 M sodium chloride. The anthrone method was used to determine the mucus present. Enprostil was found to significantly increase gastric mucus at a dose of 60 micrograms/kg when measured by the anthrone test. Enprostil administered by the oral route was most effective in stimulating mucus secretion, suggesting a local or topical action of enprostil on mucus-secreting cells. Scanning electron microscopy of rat fundic mucosa after enprostil administration (50 to 100 micrograms/kg) revealed the presence of thin veil-like layers covering the epithelial surface, which was interpreted as an increase in mucus secretion. Higher magnifications (X 2,000) clearly showed the layers of mucus covering the surface epithelial cells. Enprostil's apparent increase of gastric mucus secretion may contribute to its anti-ulcer activity and may promote gastric healing.

Gastric protection by misoprostol against 1300 mg of aspirin. An endoscopic study

Misoprostol, a synthetic prostaglandin E1 analog, is being evaluated in the treatment of peptic ulcer. It has been reported to have both antisecretory and cytoprotective properties. In this placebo-controlled, double-blind study, pretreatment with 200-micrograms doses of misoprostol was evaluated in the prevention of gastric injury caused by aspirin. Five oral doses of misoprostol or placebo were administered over 24 hr followed by a single oral 1296-mg dose of aspirin 30 min after the fifth dose of test agent. Two hours later the gastric mucosa was examined with a small-caliber fiberendoscope. Protection was defined as no more than 10 petechiae and no more than two hemorrhagic streaks in the gastric mucosa. Twenty of 30 (67%) subjects who received misoprostol was protected, whereas only one of 30 (3%) subjects receiving placebo was protected. The difference between the effects of misoprostol and placebo was highly significant (P less than 0.001). We concluded that five 200-micrograms doses of misoprostol given over 24 hr protects the gastric mucosa from the injurious effect of a single dose of aspirin.

Prostaglandins and acute pancreatitis--experimental and clinical studies

Acute pancreatitis has a mortality of 10-20 per cent, and in cases of acute haemorrhagic pancreatitis this rises to 80-90 per cent. At present there is no reliable treatment for this condition. Based on the hypothesis that the release locally and systemically of the intracellularly activated pancreatic digestive enzymes is due to cell membrane instability, we have studied the cytoprotective (cell membrane stabilizing) role of prostaglandins in this condition. In the first part of this study, an animal model of acute pancreatitis with a mortality of 100 per cent by 14 days has been established by feeding mice a choline-deficient ethionine supplemented diet. Using this model we have demonstrated improved survival (16 out of 50 survived 14 days or longer) by administering prostaglandin E2 subcutaneously (P less than 0 X 02). We have demonstrated that the improved survival is dose-dependent, in the range 2 X 5-5 X 0 mg/kg body weight 8 hourly (P less than 0 X 02) and time-dependent, still being effective if treatment is delayed for 24 h (P less than 0 X 02). Great emphasis has been placed on not commencing treatment until after the induction of acute pancreatitis. In the second part we have used cell membrane marker enzymes to study the cell membrane stabilizing effect of prostaglandin E2 in the human. It has been demonstrated that cell membrane instability occurs. In 12 of 50 episodes treated by prostaglandin E2 infusion, the lysosomal, mitochondrial and cell membranes are stabilized, thus decreasing the release of intracellular enzymes.

Role of prostaglandin E2 on human gastric ulcers

Using radioimmunoassay, we determined the mucosal prostaglandin E2 (PGE2) concentration in normal subjects and in patients with tractable and intractable gastric ulcers. The fundic and antral mucosa of the normal subjects contained large amounts of PGE2; they were not significantly different from those found in tractable and intractable gastric ulcer patients. The mucosal PGE2 concentration at the ulcer margin was significantly higher in tractable than intractable cases. To assess the effect of PGE2 on ulcer healing, 11 intractable ulcer patients received PGE2 (1.5 or 3.0 mg/day) perorally. In 7 (64%), the ulcer healed completely within 4 to 14 weeks.

Role of prostaglandin E2 on gastric ulcers induced by non-steroidal anti-inflammatory compounds (NOSAC)

We investigated the effect of indomethacin and aspirin on the prostaglandin E2 (PGE2) levels in rat gastric mucosa. In untreated controls, the PGE2 level was 1085 +/- 80 ng/g in the fundic- and 2435 +/- 339 ng/g in the antral mucosa; it was markedly reduced by indomethacin (6 or 20 mg/kg) in a dose-related manner prior to the formation of gastric ulcers. Aspirin (200 mg/kg) also decreased the mucosal PGE2 content. The simultaneous infusion of 5 microgram/kg 16, 16-dimethyl PGE2 and 20 mg/kg indomethacin inhibited the formation of gastric ulcers. Our experimental results suggested that the indomethacin- or aspirin-induced gastric mucosal lesions are due to a deficiency of endogenous mucosal PGE2.

The effect of orally administered prostaglandins on gastric mucus secretion in the rat

The secretion of gastric mucus may play a role in the protective effect of prostaglandins against gastric ulcers. To investigate the effect of prostaglandins E1, E2, F1alpha, F2alpha, A1, A2 and 15 (S) 15 methyl prostaglandin E2-methyl ester on gastric mucus secretion, these prostaglandins were given orally to rats at doses of 0.1, 1.0 and 4.0 mg/kg. The anthrone method was used to analyze the amount of mucus washed from the stomach with 2 M Nacl. Gastric secretory volume effects were also observed. All of the compounds tested increased both gastric mucus and secretory volume. The most active compound was 15(S)15 methyl PGE2 Me ester. The mucus stimulating effect of these prostaglandins, when administered locally, may be relevant to the understanding of the anti-ulcer effect of prostaglandins.

Effect of 16, 16 dimethyl prostaglandin E2 on aspirin-induced permeability changes in the pancreatic duct

Perfusion of the pancreatic duct with acidified aspirin in cats increased the permeability of the duct to HCO3-. Intravenous administration of the synthetic prostaglandin analog 16,16 dimethyl prostaglandin E2 (PGE2) prevented this permeability change. The effect was dose-related and at the highest dose (50 microgram/kg/hour) was essentially complete. The beneficial effect of the PGE2 was apparent even when it was given after the duct had been exposed to aspirin. PGE2 had no effect on pancreatic water or electrolyte secretion in the unstimulated nonsecreting gland. No histologic changes in the pancreatic ducts were seen after exposure to aspirin, PGE2 or both. The effectiveness of PGE2 in restoring membrane permeability towards normal suggests the possibility of its therapeutic role in pancreatitis.

Decrease in aspirin-induced gastric mucosal damage in rats by oral administration of the cytotoxic drugs melphalan and methotrexate

Gastric mucosal damage by aspirin and chemotherapeutic drugs was studied in Wistar rats. Aspirin 60 mg given by stomach tube caused substantial gastric mucosal damage as judged by visual examination of the stomachs removed four hours later. Melphalan and methotrexate given daily for four days had no significant macroscopic effect on the gastric mucosa, but reduced the damage caused by aspirin. This protective effect my involve a stimulation of prostaglandin synthesis by the stomach, increased mucus secretion, and/or inhibition of acid secretion.

Effect of prostaglandin E2, cimetidine, and atropine on ethanol-induced gastric mucosal damage in the rat

The effect of prostaglandin E2 (PGE2), cimetidine, and atropine on ethanol-induced gastric mucosal damage was studied in anaesthetised rats. Intravenous infusion of PGE2 (120 micrograms/kg X h) protected the gastric mucosa against lesions produced by irrigation of the stomach with 30% (v/v) ethanol in 100 mM HCl plus 50 mM NaCl. PGE2 had no effect on back-diffusion of H+ ions, whereas outflow of Na+ and K+ ions decreased. The increases in pepsinogen secretion and gastric mucosal blood flow during mucosal damage were not affected by PGE2. Cimetidine (25 mg/kg intravenously) failed to prevent mucosal haemorrhages induced by ethanol. Cimetidine caused a slight decrease in outflow of Na+ ions but otherwise had no effect on the variables measured. Atropine sulphate (1 mg/kg X h intravenously) similarly did not protect the gastric mucosa against ethanol-induced lesions, nor did it change ion fluxes, fluid output, or pepsinogen secretion during mucosal damage. Gastric mucosal blood flow, however, was lower in the atropine-treated rats than in the control rats. The results indicate that PGE2, but not cimetidine or atropine, protects the gastric mucosa against ethanol-induced damage in anaesthetised rats, but that this effect is not due to prevention of back-diffusion of H+ ions or to increased mucosal blood flow.

The effects of a prostaglandin endoperoxide analogue on canine gastric acid and mucus secretion

The effects of U-46619, a stable analogue of the prostaglandin endoperoxide PGH2, were studied on canine gastric acid secretion, gastric mucosal blood flow, and secretion of mucus into gastric juice and compared to those of PGE2. U-46619 was approximately four and three times as potent as PGE2 in inhibiting acid secretion and stimulating mucus secretion, respectively. When infused at a low dose, U-46619 inhibited acid secretion directly without causing a decrease in the ratio of mucosal blood flow to volume rate of secretion (R), this effect being similar to that observed for PGE2. However, unlike PGE2, U-46619 when administered in a higher dose caused a decline in R while decreasing acid secretion and mucosal blood flow, suggesting a primary restriction of blood flow. The antisecretory effects of arachidonic acid may be due in part to the endogenous formation of prostaglandin endoperoxides as opposed solely to prostaglandin formation. Considering the antisecretory and mucogenic actions of U-46619, nontoxic analogues of prostaglandin endoperoxides may be of value as antiulcer agents.

Inhibition of harmaline induced tremors by 16 (S)-16-methyl PGE2 in different mammalian species: a correlation with central cyclic nucleotides and prostaglandins

Harmaline, an alcaloid of Paganum Armala, induces tremors of central origin and increases cerebellar cGMP without affecting cortical and cerebellar prostaglandin levels. 16(S)-16-methyl PGE2 protects the animals against the seizures induced by the alcaloid and prevents the concomitant rise in cerebellar cGMP. Experiment performed in cats and limited to pharmacological observations, confirmed that, the PGE2 derivative, is a powerful antitremorogenic agent at doses that are devoid of appreciable side effects.

Stimulation of mucus and nonparietal cell secretion by the E2 prostaglandins

The effects of prostaglandin E2 (PGE2), 15-methyl prostaglandin E2 (15M), and 16,16-dimethyl prostaglandin E2 (16DM) on gastric mucus and nonparietal cell secretion in rats were measured. Alcian blue binding was used as a measure of gastric mucus. Applied topically, all three agents stimulated nonparietal cell secretion, and PGE2 and 16DM stimulated the secretion of mucus, increasing the fraction in the gastric contents but not that adherent to the mucosa. Topical 15M did not stimulate the production of mucus. Given intranveously, all three agents increased the amount of mucus in the gastric contents without altering the amount of mucus bound to the mucosa. The prostaglandins had no effect on nonparietal cell secretion when given intravenously. These effects could be relevant to the ability of the E2 prostaglandins to protect the gastric mucosa from damage.

Estimation and characterization of prostaglandins in the human gastrointestinal tract

1 Prostaglandin-like material was extracted from muscle and mucosa of surgically removed human stomach, ileum and colon and assayed against prostaglandin E(2) on strips of rat gastric fundus. Superfused human isolated gastric mucosa released prostaglandin-like material and release was increased by stretching or clamping the tissue.2 The relative amounts of extracted biological activity were broadly as follows: gastric antral mucosa > colon muscle > gastric body mucosa approximately ileal mucosa > colon mucosa approximately gastric muscle approximately ileal muscle.3 Prostaglandin E and F were tentatively identified by chromatography and sensitivity to inactivation by alkali.4 Prostaglandin E apparently contributed most to the biological activity, possibly because the assay tissue is more sensitive to prostaglandin E than to F. Chromatography of gastric body mucosal extracts located material running with prostaglandin E(2) and a little with E(1). Colonic muscle and mucosal extracts contained material with R(F) values of prostaglandins E(1), E(2), E(3) and F(1a), whereas F(2a) and F(3a)-like substances were found only in the mucosa. The proportions of prostaglandin F varied between specimens.5 The amount of extracted prostaglandin-like activity was increased by adding cofactors and arachidonic acid, and lessened by homogenization with acid-ethanol.6 The type and amount of activity generated from arachidonic acid by partly purified colonic mucosal prostaglandin synthetase depended on the substrate concentration.7 The possible relationships of prostaglandins to mucus secretion and other physiological and pathological gut functions are discussed.

On the synthesis of prostaglandins by human gastric mucosa and its modification by drugs

1. Specific radioimmunoassays for the prostaglandins E2, A2 and F2alpha were used to study the synthesis of prostaglandins by gastroscopically obtained small biopsy specimens of human gastric corpus mucosa. 2. Both prostaglandin E2 and prostaglandin F2alpha were found to be synthesized from arachidonic acid by themicrosomal fraction of human gastric mucosa. The synthesis of prostaglandin E2 exceeded that of prostagladin F2alpha by a factor of about 10. 3. Synthesis of prostaglandin A2 or prostaglandin B2 was not observed under the same incubation conditions. 4. Indometacin effectively inhibited synthesis of both prostaglandin E2 (ID50 4.2 microng/ml) and prostaglandin F2alpha (ID50 1.8 microng/ml) by human gastric mucosa, while paracetamol even in a concentration of 310 microng/ml did not influence prostaglandin synthesis. The anti-ulcer agent carbenoxolone, which has been shown to inhibit prostaglandin inactivation, at the same concentration only slightly inhibited (about 20%) prostaglandin synthesis. 5. The results support the hypothesis that the gastro-intestinal effects or side effects of several drugs are mediated by an influence on the enzymes of prostaglandin synthesis or inactivation.

Effect of 15 (R) 15 methyl prostaglandin E2 on the healing of gastric ulcers: a double-blind endoscopic study

A double-blind trial was carried out to assess the effect of 15 (R) 15 methyl prostaglandin E2 on the healing of gastric ulcers. The prostaglandin preparation was given orally in doses of 150 mug every 6 hours for two weeks to 10 subjects with proven gastric ulcer. The control group consisted of 10 subjects with proven gastric ulcer, who did not receive prostaglandin treatment. All were in hospital, and at rest in bed. Ulcer healing was assessed endoscopically with a duodenofibrescope. The maximum diameter of the ulcer crater was determined endoscopically just before and after two weeks of treatment. In the prostaglandin group, complete healing was seen in three cases and considerable healing (50% and more) in five cases, and the overall mean healing rate was 63-3%. In the control group, complete healing was seen in no case and considerable healing in one case, and the overall mean healing rate was 17-1%. The difference was highly significant. The results confirm the belief that 15 (R) 15 methyl prostaglandin E2 is effective in promoting the healing of gastric ulcers.20