Prostaglandin prevents alterations in DNA, RNA, and protein in damaged gastric mucosa

Mechanisms of nonsteroidal anti-inflammatory drug-induced gastric damage

The effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on the gastric mucosa are well documented. The complex mechanisms of gastric damage, however, are not fully understood. This review examines current knowledge about the normal function of the gastric mucosal barrier; the role of prostaglandins in cytoprotection and repair; the mechanisms by which aspirin and other weak organic acids are absorbed by the stomach; and the subsequent cascade of events--including ion trapping and back diffusion of hydrogen ions--that leads to gastric erosion and bleeding. A hypothesis describing NSAIDs' dual insult on the stomach is advanced.

Intraportal prostaglandin E1 ameliorates the toxicity of intraportal 2'-deoxy-5-fluorouridine in rats

This study was designed to see whether intraportal infusion with prostaglandin E1 (PGE1) could reduce mortality associated with high-dose intraportal infusion of 2'-deoxy-5-fluorouridine (FUDR). Thirty anesthetized male Sprague-Dawley rats underwent laparotomy and placement of osmotic pumps (Alzet 2ML1) infusing a branch of the portal vein. Animals were weighed and infused for 1 week with buffer (control), FUDR (3 mg/kg/day), or FUDR (3 mg/kg/day) + PGE1 (0.1 microgram/kg/min). Blood was then obtained for liver functions and white blood cell count. The body and liver were weighed. No animals died in the control group. Five animals in the FUDR group died during the fourth (n = 1), sixth (n = 2), and seventh (n = 2) days of infusion. Only one animal in FUDR + PGE1 group died during the sixth day of infusion. Weight loss was greater in both treated groups than in controls. Animals receiving PGE1 lost significantly less weight than animals receiving FUDR alone. These data suggest that intraportal PGE1 ameliorates the hepatic toxicity of intraportal FUDR. The effect of PGE1 on the tumoricidal properties of FUDR infused by either the portal vein or the hepatic artery remains to be studied.

Circadian rhythmicity of acid secretion and electrical function in intact and injured rat gastric mucosa--the relation of timing to ulcerogenesis

Alteration of electrical function in mammalian gastric mucosa is considered as an indicator of gastric barrier rupture. Measurements of transmucosal potential difference (PD) and electrical resistance (R) have documented such alterations to a variety of mucosal damaging agents. This study was designed to test whether the rat gastric mucosa exhibits circadian rhythms in acid secretion and electrical function and whether the damage produced by a mucosal acting agent (butyric acid) is also circadian-stage dependent. Mucosa was isolated from the gastric body of male rats standardized from birth to a light-dark regimen. Circadian rhythms of acid secretion and PD and R with acrophases during the dark hours were documented. Administration of butyric acid produced circadian-stage dependent damage with an acrophase also during the dark-phase span. Thus, in this experimental model, measurements of electrical function represented a poor index of gastric mucosal susceptibility to damaging agents. The authors discuss the possibility that rhythms other than those related to electrical function may better define mucosal vulnerability to ulcerogenesis.

Gastric antisecretory, gastric and duodenal anti-ulcer and cytoprotective properties of Ro 22-6923, a synthetic trimethyl prostanoid in rats

Ro 22-6923, a synthetic trimethyl prostanoid, has been studied for its ability to inhibit gastric secretion and to protect the gastroduodenal mucosa against the injuries caused by pyloric ligation, hypothermic restraint stress, nonsteroidal anti-inflammatory drugs (NSAIDs), reserpine, dimaprit, cysteamine and the cytodestructing agents--80% ethanol, 0.6 M HCl, 0.2 M NaOH, 25% NaCl, aspirin 30 mg in 0.35 M HCl and 100 mM sodium taurocholate in 0.2 M HCl. The results of this study demonstrate that Ro 22-6923 has both prophylactic and curative effects on various experimental models. It produces a dose dependent inhibition of the gastric mucosal damage induced by pyloric ligation, hypothermic restraint stress, NSAIDs, reserpine, dimaprit and cytodestructing agents and that of duodenal ulcers induced by cysteamine. It also produces a dose dependent healing of the acetic acid induced chronic gastric ulcers. These observations suggest that Ro 22-6923 exerts its anti-ulcer effects by its antisecretory, gastric mucosal resistance increasing and cytoprotective activities and that it may be a useful therapeutic agent for the treatment of peptic ulcer disease in humans.

The effect of tiaprofenic acid and indomethacin on in vitro prostaglandin synthesis by rat, rabbit and human stomach tissue

We compared the inhibitory effect of two non-steroidal anti-inflammatory drugs (NSAIDs), tiaprofenic acid and indomethacin, on in vitro prostaglandin (PG) synthesis by human, rat and rabbit stomach/duodenal tissue. Both drugs were equipotent inhibitors of PGE2, 6-oxo-PGF1 alpha (the stable metabolite of prostacyclin, PGI2) and PGF2 alpha. These findings suggest that tiaprofenic acid does not offer 'gastric protection' by sparing the cytoprotective PGs, as previously claimed. Our in vitro findings are in agreement with the results of clinical trials which show that faecal blood loss and epigastric discomfort are of a similar pattern whether tiaprofenic acid or other NSAIDs are administered.

Prostaglandins and the gastrointestinal mucosa: are they important in its function, disease, or treatment?

In 1971 interest in the role of prostaglandins in the gastrointestinal tract was stimulated by the publication of two hypotheses--that aspirin damaged the gastric mucosa by inhibiting prostaglandin synthesis (1) and that cholera toxin caused diarrhea by stimulating it (2). Subsequent research into the gastrointestinal actions of prostaglandins has been considerable and now impinges on clinical practice. This paper reviews the involvement of prostaglandins and related compounds in mucosal protection, in ulcer healing, in diarrhea, and in gastrointestinal inflammation, with particular reference to the growing body of human data.

Gastric mucosal damage in sepsis--effects of pretreatment with a synthetic prostaglandin E1 analogue

An experimental model was used which includes intragastric instillation of 80 mM HCl and 0.6 ml bile/kg followed by intravenous infusion of live E coli in cats for up to three hours. This procedure regularly induces gastric mucosal ulcerations. Mucosal blood flow was measured by microspheres before, early, and late in sepsis. Total gastric blood flow was recorded electromagnetically. Mucosal regeneration capacity as reflected by the RNA/DNA ratio was measured. Misoprostol (a PGE1 analogue) was infused iv (5 micrograms/kg X h) or given locally in the stomach (10 micrograms/kg) before bacteriemia. Misoprostol did not influence the haemodynamic response to bacteria. The gastric mucosal damage was assessed either as an index representative for the entire corpus-fundus region or as the number of areas with intact surface epithelium within the series. Misoprostol iv protected the mucosa from ulceration compared with untreated septic controls while misoprostol intragastrically significantly reduced the number of damaged areas only. Topical misoprostol increased total gastric and mucosal blood flows early in sepsis compared to iv or no pretreatment while no difference was seen during late sepsis. The protective effect of misoprostol was thus not dependent on increased gastric mucosal blood flow. Nor was it mediated through effects on mucosal nucleic acid concentrations or ratio.

Gastric antral and fundic mucosal protein, DNA and RNA changes in different experimental ulcer models

The changes in gastric (fundic and antral) mucosal protein, DNA and RNA content, have been investigated in different experimental gastric ulcer models of rat. It seems that indomethacin and stress (restraint) ulcer formation were followed by a predominant fundic (oxyntic cell area) mucosal DNA increase, while in the antral mucosa this phenomenon was connected to a significant RNA increase. The observed changes of the RNA/DNA ratio in the fundic mucosa were interpreted as a sign of accelerated cell renewal. The authors conclude that during ulceration the regenerative processes concomitantly take place.

Evaluation of the protection of rat gastric mucosa by a prostaglandin analogue using cellular enzyme marker and histologic techniques

Damage to the rat gastric mucosa after oral administration of ethanol and the effect of pretreatment with a prostaglandin analogue has been evaluated using histologic and enzyme-marker techniques. Rat whole stomachs were incubated in vitro and the intraluminal release of the cytoplasmic enzyme lactate dehydrogenase and the lysosomal enzymes acid phosphatase and beta-glucuronidase was determined by spectrophotometric techniques. Ethanol irrigation in vivo for 10 min significantly elevated the subsequent intraluminal release of both cytoplasmic and lysosomal enzymes in vitro. Pretreatment with 16,16-dimethyl prostaglandin E2 (0.1-1.25 microgram/kg p.o.) in doses that substantially inhibited the formation of macroscopically apparent necrotic lesions failed to prevent enzyme release. However, higher doses of the prostaglandin analogue (2.5-20 micrograms/kg) did significantly reduce the intraluminal release of the cellular enzymes, with the lysosomal enzymes being more readily inhibited. Histologic studies confirmed that the lower doses of the prostanoid prevented deep tissue necrosis and vasocongestion, yet did not protect surface epithelial cells from ethanol-induced damage. However, with the highest dose of 16,16-dimethyl prostaglandin E2 (20 micrograms/kg) a significant reduction in the extent of damage to the superficial epithelial cells was observed, suggesting a correlation with the findings using enzyme markers of cell damage. The apparent protective mechanisms of this prostanoid under the present conditions may involve mucus and fluid effusion that could allow restitution of the surface epithelial layer.