Time-course studies of the distribution of [1-14C]acrylonitrile in rats after intravenous administration

Intravenous injection of acrylonitrile (ACN) causes adrenal hemorrhagic necrosis. ACN and its metabolites react with glutathione and bind covalently with macromolecules. Hence the purpose of this investigation was to measure the distribution and covalent binding of radiolabel derived from [1-14C]ACN in order to determine whether binding of ACN or its metabolites may be implicated in the pathogenesis of ACN-induced adrenal injury. Following intravenous injections of ACN, concentrations of total radiolabel were highest in the blood, liver, duodenum, kidneys, and adrenals. Except for blood, there was a time-dependent decrease in total radiolabel in these tissues. Compared with other major organ systems, the levels of covalently bound radiolabel were lower in the adrenal glands. These results do not support a role of covalent binding of ACN or its metabolites in the adrenal toxicity of ACN, but suggest that the initial high concentrations of total radiolabelled compounds derived from ACN could play a role in the action of ACN on the adrenal glands.

Gastric mucosal protection by agents altering gastric mucosal sulfhydryls. Role of endogenous prostaglandins

Intragastric administration of sulfhydryl-containing cysteamine or sulfhydryl-oxidizing diethylmaleate caused a dose-dependent reduction in the mean area of gastric lesions induced by absolute ethanol. The protective effects of these agents are abolished by the sulfhydryl blocker N-ethylmaleimide, while indomethacin, a potent inhibitor of cyclooxygenase, caused only about 50% reduction in this protection. This study indicates that mucosal generation of prostaglandins contributes to the gastric cytoprotection by these agents administered intragastrically, but endogenous sulfhydryls are also involved in the gastric mucosal protection by sulfhydryl-containing or sulfhydryl-oxidizing compounds.

Gastric mucosal protection by acetazolamide derivatives: role of carbonic anhydrase and sulfhydryls

Acetazolamide, a carbonic anhydrase inhibitor, prevents acute gastric hemorrhagic lesions induced by ethanol. We used acetazolamide and other carbonic anhydrase inhibitors to correlate their gastroprotective effects with the degree of inhibition of carbonic anhydrase. Since acetazolamide is a thiadiazole, we also investigated structurally related thiadiazoles that contain sulfhydryls to test the hypothesis that the protection against ethanol-induced gastric erosions is related to the presence of sulfhydryls. Dose-response studies with acetazolamide revealed that the protection did not correlate with the inhibition of carbonic anhydrase in the rat gastric mucosa. The carbonic anhydrase inhibitors sulfanilamide and ethoxzolamide, did not offer protection. Bismuthiol I, a thiadiazole with two sulfhydryls, was twice as protective as 2-amino-5-mercapto-1,3,4-thiadiazole with only one sulfhydryl group. We conclude that the protection by acetazolamide against ethanol-induced lesions is not related to the inhibition of carbonic anhydrase in the gastric mucosa. The gastroprotective effect of acetazolamide and its derivatives may be related to their content of sulfhydryls in an oxidized or reduced state.

Prevention of ethanol-induced vascular injury and gastric mucosal lesions by sucralfate and its components: possible role of endogenous sulfhydryls

We tested the hypothesis that sucralfate, which contains eight sulfate and aluminum molecules on a sucrose and its other components might decrease ethanol-induced vascular injury and hemorrhagic mucosal lesions through a sulfhydryl (SH)-sensitive process. Experiments performed in rats revealed that the entire sucralfate molecule is not a prerequisite for protection against ethanol-induced mucosal vascular injury and erosions. It appears that sulfate and sucrose octasulfate are potent components of sucralfate, although an equimolar amount of sucralfate is at least twice as effective in gastroprotection than its components. The SH alkylator N-ethylmaleimide abolished the gastroprotection by sucralfate, suggesting SH-sensitive process in the mucosal protection which seems to be associated with the prevention of rapidly developing vascular injury in the stomach of rats given ethanol.

Ethanol-induced acute gastric injury in mast cell-deficient and congenic normal mice. Evidence that mast cells can augment the area of damage

The authors used stereomicroscopy and planimetry to measure the area of glandular stomach mucosa acutely injured by oral ethanol in mast cell-deficient and congenic normal (+/+) mice, and examined the damaged areas in 1-mu sections. Ethanol caused degranulation and/or disruption of gastric mucosal mast cells, and, at certain concentrations of ethanol, mast cell-deficient WBB6F1-W/Wv or WCB6F1-Sl/Sld mice developed significantly less (43-90% less) acute gastric injury than either congenic +/+ mice or WBB6F1-W/Wv mice whose mast cells were restored by bone marrow transplantation from WBB6F1-+/+ mice. Nevertheless, ethanol produced detectable, and in some cases substantial, gastric injury even in the complete absence of mast cells. Thus, ethanol can produce some damage to the gastric mucosa independently of mast cells. But these data suggest that under certain circumstances mast cells can augment the area of acute gastric injury induced by ethanol.

Role of lipid peroxidation in gastric mucosal lesions induced by HCl, NaOH, or ischemia

We investigated whether lipid peroxidation is an important biochemical mechanism in acute gastric mucosal injury induced by acid, base, or postischemic reperfusion. Lipid peroxidation products, i.e., the concentration of conjugated dienes (absorbance at 242 nm), products absorbing at 270 nm, and malondialdehyde were measured in the gastric mucosa of rats killed 30 s or 1, 3, or 6 min after intragastric (ig) administration of 0.6 N HCl or 0.2 N NaOH. No increase in any of the lipid peroxidation products was detected at any of the time intervals. Mucosal lesions, however, were already visible at 30 s. Cumene hydroperoxide (1 ml, 100 mM ig) induced neither mucosal lesions nor lipid peroxidation. In vitro incubation of mucosal homogenates with cumene hydroperoxide (1 or 10 mM) however, rapidly induced elevation of the three parameters of lipid peroxidation. Ischemia induced by clamping the blood vessels of the stomach for 20, 30, and 40 min followed by reperfusion for 10, 30, and 40 min did not induce lipid peroxidation, despite the development of hemorrhagic mucosal lesions. Similarly, in gastric mucosal lesions induced by hemorrhagic shock no lipid peroxidation products were detected. In the small intestine, however, prolonged ischemia (2 h) followed by reperfusion (30 min) resulted in mucosal necrosis and elevation of malondialdehyde levels. These results suggest that lipid peroxidation is not a major pathogenetic mechanism in rapidly developing acute gastric mucosal injury caused by 0.6 N HCl or 0.2 N NaOH, or in the more slowly developing mucosal injury caused by postischemic reperfusion.

Infections associated with transhepatic biliary drainage devices

To determine the infectious complications associated with transhepatic biliary drainage devices, an analysis of the records of 38 patients who underwent placement of a pigtail catheter (n = 11), a Ring catheter/feeding tube (n = 13), or a Carey-Coons endoprosthesis (n = 15) was carried out. Nineteen infectious events occurred in 38 patients with 39 biliary devices. Infections consisted of bacteremia, cholangitis with and without documented bacteribilia, and intrahepatic abscesses and were frequently associated with obstruction (66.7 percent of infectious episodes). The most frequent organisms isolated from blood were Escherichia coli and Pseudomonas aeruginosa, and the most frequent organisms isolated from bile were P. aeruginosa, Klebsiella pneumoniae and Streptococcus faecalis. Trends for more frequent occurrence of neoplasms involving the gallbladder or biliary tract, recent surgical procedures and catheter manipulations in infected as compared with noninfected patients, and a delayed time to infection were noted in patients with an endoprosthesis.

Development of cysteamine-induced ultrastructural surface changes on duodenal mucosa

Duodenal ulcers were induced acutely in female rats by a single oral administration of cysteamine, 70 mg/100 gm, in order to study morphologic progression of lesion development from the perspective of cellular surface changes by scanning electron microscopy. Thick sections of resin-embedded specimens were also studied by light microscopy, and animals were sacrificed at intervals of 30 minutes, 1, 2, 4, 8, 12, 20, and 24 hours post-treatment. Earliest evidence of cytologic lesions was apparent at 2 hours and data confirmed earlier reports that alterations began at villous tips. Both cellular sloughing and in situ cellular injury were evident, the latter phenomenon constituting the principal mode of cysteamine-induced erosion. In situ change began, from surface perspective, as a minute cavitation on the apical aspect of an isolated, single epithelial cell which was surrounded by normal cells. These early lesions progressed to in situ necrosis either of isolated cells or of small clusters of adjacent cells. This phenomenon occurred concurrently on multiple villi, all within the localized site at which cysteamine-induced duodenal ulcers are known to develop. An additional early morphologic change was the occasional appearance of a background of pleomorphic cellular apices of variable size on the villous ridges. By 8 to 12 hours, cellular damage advanced to erosions with some cells in the preulcer area still showing initial stages of in situ cellular injury. Precipitated mucus on the surface was increased in the preulcer area, and by 20 to 24 hours typical duodenal ulcers were evident. These scanning electron microscopic data confirm the significance of surface damage at villous tips very early in the cysteamine-induced ulcerogenesis. The present higher resolution findings demonstrated that earliest cellular damage, principally in situ cell injury, occurred simultaneously at multiple sites in the preulcer zone rather than at a single cluster of cellular damage which enlarges peripherally.

Effect of tyrosine administration on duodenal ulcer induced by cysteamine in the rat

Duodenal ulcers were produced by administering cysteamine to rats. Pretreatment with the catecholamine precursor, L-tyrosine (40 mg/100 g i.p. for 5 days), decreased the intensity of duodenal ulcers induced by cysteamine. Equimolar doses of tyrosine methyl ester (51.2 mg/100 g i.p. or s.c.) were equally effective in reducing ulcer intensity. Other amino acids (i.e., alanine, aspartic acid, glutamic acid, glycine, leucine, lysine, tryptophan and valine) did not prevent experimental duodenal ulcers. Coadministration of other large neutral amino acids (e.g., leucine and valine) that compete with tyrosine for uptake into the brain did not inhibit the effect of tyrosine on duodenal ulcers induced by cysteamine. Gastric, duodenal and brain dopamine concentrations were increased 1 hr after the injection of tyrosine methyl ester (25.6 mg/100 g s.c.). These results suggest that the effect of tyrosine on duodenal ulcer induced by cysteamine may be mediated by changes in gastrointestinal dopamine metabolism.

Effect of dopamine-related drugs on duodenal ulcer induced by cysteamine or propionitrile: prevention and aggravation may not be mediated by gastrointestinal secretory changes in the rat

Dose- and time-response studies have been performed with dopamine agonists and antagonists using the cysteamine and propionitrile duodenal ulcer models in the rat. The experiments demonstrate that the chemically induced duodenal ulcer is prevented by bromocriptine, lergotrile and reduced by apomorphine or L-dopa. Aggravation of cysteamine-induced duodenal ulcer was seen especially after (-)-butaclamol, (-)-sulpiride, haloperidol and, less effectively, after other dopaminergic antagonists. The duodenal antiulcerogenic action of dopamine agonists was more prominent after chronic administration than after a single dose, whereas the opposite was found concerning the proulcerogenic effect of dopamine antagonists. In the chronic gastric fistula rat, both the antiulcerogens bromocriptine or lergotrile and the proulcerogens haloperidol, pimozide or (-)-N-(2-chlorethyl)-norapomorphine decreased the cysteamine- or propionitrile-induced gastric secretion. No correlation was apparent between the influence of these drugs on duodenal ulcer development and gastric and duodenal (pancreatic/biliary) secretions. In the chronic duodenal fistula rat, decreased acid content was measured in the proximal duodenum after haloperidol, and diminished duodenal pepsin exposure was recorded after bromocriptine. Furthermore, the aggravation by dopamine antagonists of experimental duodenal ulcer probably involves a peripheral component. The site of dopamine receptors and physiologic effects which modulate experimental duodenal ulcer remain to be identified, but their elucidation may prove to be an important element in the pathogenesis and treatment of duodenal ulcer.

Biochemical changes in tissue catecholamines and serotonin in duodenal ulceration caused by cysteamine or propionitrile in the rat

Previous structure-activity and pharmacologic studies with duodenal ulcerogens cysteamine and propionitrile implicating catecholamines in the pathogenesis of duodenal ulceration have now been followed up by dose- and time-response biochemical investigations to assess the importance of monoamines in the development of duodenal ulcers. The concentrations of norepinephrine (noradrenaline), dopamine, serotonin and their metabolites were measured in total brain, brain regions, stomach, duodenum, pancreas and adrenals in the rat. Turnover of catecholamines was determined in rats pretreated with the inhibitor of tyrosine hydroxylase alpha-methyl-p-tyrosine. The duodenal ulcerogens caused a dose- and time-dependent depletion of norepinephrine in virtually all the tissues examined. The effect was maximal 4 or 7 hr after cysteamine or propionitrile, and norepinephrine levels returned to normal in 24 hr. Dopamine changes were selective and often biphasic, e.g., elevation in adrenals, biphasic in brain cortex, hippocampus and midbrain, but uniformly decreasing in glandular stomach and duodenum. In the median eminence dopamine levels decreased by 181 and 324% at 15 and 30 min, respectively, after cysteamine, but neither dopamine nor 3,4-dihydroxyphenylacetic acid was modified in the periventricular nucleus. Serotonin levels were relatively stable, revealing slight elevations or no changes in most of the tissues. The turnover of norepinephrine was accelerated by both chemicals in virtually all brain regions, but dopamine turnover was affected only in a few areas, e.g., in the corpus striatum and medulla oblongata cysteamine decreased dopamine turnover, whereas propionitrile first (at 1 hr) accelerated then (at 8 hr) significantly suppressed it.(ABSTRACT TRUNCATED AT 250 WORDS)

Early ultrastructural changes in rat duodenal mucosa associated with cysteamine-induced ulcer

The early morphologic sequelae induced by the duodenal ulcerogen, cysteamine, have been studied in rats by transmission electron microscopy. Cysteamine was administered per os at 70 mg/100 g body wt to groups of female rats sacrificed at 30 min, 1, 2, 4, 8, 12, 20, and 24 hr after chemical treatment, and duodenal tissue sampled from the antimesenteric side of the proximal duodenum, where ulcers develop, was studied. Emphasis was placed on early times as our previous scanning electron microscopic data had demonstrated enhanced in situ cellular necrosis and surface cavitation at 2-4 hr after cysteamine treatment. Results indicated intracellular changes as early as 30 min after treatment and prior to damage of the columnar cell microvilli or epithelial tight junctions. A staging of observed cellular degenerative changes suggested early apical endoplasmic reticular swelling and loss of cytoplasmic ground substance, followed later by moderate internal disruption of mitochondria. Through these stages the cell surface microvilli remained morphologically normal. Subsequently, microvilli degenerated and mitochondrial fine structure became severely disrupted and cell contents were expelled. Deeper villous changes such as separation of columnar cells from the lamina propria and alterations of selected elements within the lamina propria were observed. These data suggest that intracellular cytotoxic reactions at the villous tips occur early and may precede the influence of intraluminal damaging factors induced by cysteamine.

Development and significance of cysteamine and propionitrile models of duodenal ulcer

Cysteamine is widely used in rodents to induce duodenal ulcer. Herein, the pathogenesis of duodenal ulceration in its earliest stages was reviewed using findings from cysteamine- and propionitrile-induced duodenal ulcer in rodent models, especially taking into account changes in the secretion of gastric acid, duodenal and pancreatic bicarbonate as well as gastroduodenal motility. The effect of cysteamine-HCl in inducing ulcers in rats is circadian rhythm-dependent. The effect is greatest from just before the end of diurnal rest to just after the start of nocturnal activity. The chronobiologic effect may be in part due to the circadian rhythm-dependent increased gastric acid production from cysteamine. Titratable acidity was found to be twice as great in the gastric juice of rodents when cysteamine was given by injection at 2000 (just after the start of nocturnal activity) in comparison to when given at 0800 or 1200 (at the beginning or middle span of daily rest). Further studies have shown that adrenalectomy of rats 7 days before cysteamine administration obliterated the observed circadian susceptibility to ulcer formation. Duodenal ulceration, at least in the cysteamine model, appears to be under chronobiologic neuroendocrine control or influence, seemingly mediated by the adrenal glands.

Ethanol-induced damage to mucosal capillaries of rat stomach. Ultrastructural features and effects of prostaglandin F2 beta and cysteamine

Impairment of the mucosal microcirculation may contribute to ethanol-induced gastric mucosal damage. In this report, we describe diffuse and severe ultrastructural damage to the capillaries of the gastric glandular mucosa of the rat that occurred within 1 min after intragastric instillation of 100% ethanol. There was a gradient of damage in that endothelial cell structure was most severely disrupted in profiles of capillaries located close to the luminal surface but some morphologic evidence of damage was evident in the wall of capillary profiles to a mean depth of 256 micron. Capillary structure was generally normal in the deeper regions of the mucosa. Pretreatment with intragastric cysteamine, 30 mg/100 g, or intragastric prostaglandin F2 beta, 0.5 mg/100 g, significantly reduced the depth in the mucosa to which damage to capillaries extended. Pretreatment with intragastric prostaglandin F2 beta, 0.2 mg/100 g, afforded no significant protection. We conclude that a 1-min exposure to 100% ethanol induces striking damage to the microcirculation of glandular mucosa of the rat stomach with severe damage to capillary profiles near the lumen and sparing of capillary profiles near the muscularis mucosa, and pretreatment with the sulfhydryl agent, cysteamine, or with a large dose of prostaglandin F2 beta reduces the extent of but does not abolish ethanol-induced damage to gastric mucosal capillaries.

Mechanisms of gastric cytoprotection

Gastric cytoprotection is a real but relative phenomenon that is induced by both endogenous and exogenous compounds. The key element in acute mucosal protection is the preservation of vascular integrity and the resulting maintenance of blood flow. The critical factors in chronic mucosal protection include the stimulation of bicarbonate and mucus secretion, and the proliferation of epithelial, endothelial, and mesenchymal cells. Investigations are currently underway to identify the biochemical targets of cytoprotection.

Mechanisms of mucosal injury in the stomach and duodenum: time-sequence analysis of morphologic, functional, biochemical and histochemical studies

This review is based on results from our laboratory and those published by others, and is focused on the early stages of pathogenesis that can be studied mostly in animals. Gastric mucosal injury is analysed on the examples of ethanol- and aspirin-induced lesions. Ethanol (50-100%) rapidly penetrates the mucosa, causes directly and/or indirectly (e.g., release of vasoactive products) endothelial damage in superficial and deep capillaries and venules. The vascular damage results in increased vascular permeability and decrease in blood flow leading to complete circulatory standstill in superficial capillaries 1-2 min after intragastric administration of concentrated ethanol. The direct chemical damage to surface mucosal epithelium is then followed by hypoxia and deep hemorrhagic necrosis in 1-5 min (erosion or ulcer). Unionized aspirin initiates a similar and complex yet slower progressing and less extensive erosion than alcohol. Duodenal erosion and ulcer produced by cysteamine, mepirizole or MPTP are preceded by excess acid in the proximal duodenum. This could be due to increased gastric acid output (1-4 hr), decreased bicarbonate secretion or duodenal dysmotility (0.5-8 hr) preventing the proper mix of acid and base in duodenal bulb. Necrosis and desquamation of absorptive cells in duodenal villi are evident 2-4 hr, followed by villus amputation (4-8 hr), erosion and ulcer (8-24 hr). The pathogenesis of gastroduodenal mucosal injury can thus be reconstructed from results obtained with animal models and from human studies. The results should serve as a basis to design protective drugs that are active on the basis of pathogenetic events.

Early microcirculatory stasis in acute gastric mucosal injury in the rat and prevention by 16,16-dimethyl prostaglandin E2 or sodium thiosulfate

We used in vivo microscopy and laser-Doppler velocimetry to examine the effects on the gastric mucosal microcirculation and in gastric mucosal blood flow of agents that induce acute gastric mucosal damage. In vivo microscopic observation of superficial mucosal capillaries revealed vascular stasis within a mean of 54, 81, or 61 s after 100% ethanol, 0.6 N HCl, or 0.2 N NaOH, with the subsequent development of hemorrhagic mucosal lesions. Mucosal blood flow estimated by laser-Doppler velocimetry decreased by 30% at 5 min after luminal application of 100% ethanol, and decreased further to about 40% of basal levels by 15 min. The decreased mucosal blood flow 15 min after application of 50% ethanol correlated with the extent of hemorrhagic mucosal lesions. Examination of the submucosal vessels that supply and drain the mucosa showed moderate dilation of small arterioles 1, 3, and 6 min after exposure to 100% ethanol but there were no consistent changes in venules. Mild vasoconstriction of small- and medium-sized venules could be detected 6, 10, and 15 min after NaOH but not after exposure to HCl. Pretreatment with 16,16-dimethyl prostaglandin E2 or sodium thiosulfate before exposure of the mucosa to ethanol prevented capillary stasis, maintained mucosal blood flow, and prevented the development of hemorrhagic gastric mucosal lesions. Topical mucosal application of 16,16-dimethyl prostaglandin E2 decreased, whereas topical exposure to sodium thiosulfate increased gastric mucosal blood flow, indicating that change in blood flow per se is an unlikely mediator of protection.

Protection by metals against ethanol-induced gastric mucosal injury in the rat. Comparative biochemical and pharmacologic studies implicate protein sulfhydryls

Recent evidence suggests a role of endogenous sulfhydryls (SHs) in gastric "cytoprotection." Because divalent metals bind to or oxidize SH groups, their effect on ethanol-induced gastric erosions was studied. For comparative biochemical studies the SH cysteamine, the glutathione depletor diethylmaleate. and SH alkylating agent N-ethylmaleimide (NEM) were also used. Rats pretreated with CdCl2, ZnCl2, or Cu(NO3)2 6 h before absolute ethanol showed a significant dose-dependent decrease in the mucosal lesions. Copper was effective in preventing the lesions up to 15 min before the ethanol. Iron and manganese were active at 30 min, but not at 6 h before the ethanol lesions. Indomethacin administration decreased the protection afforded by iron, manganese, and cadmium, but did not modify that by lead and copper. N-ethylmaleimide abolished the protection by iron, manganese, and cadmium, but did not affect the protection caused by lead and copper when given after the metals. However, when NEM was given before lead and copper, it diminished the protection. Secretory studies revealed that cadmium and zinc slightly inhibited gastric acid secretion, but a similar reduction of acid output by cimetidine did not decrease the ethanol-induced gastric erosions. Biochemical studies of endogenous SH showed that the protective metals and NEM decreased the glutathione concentration in the nonprotein fraction, whereas these metals diminished and NEM, which antagonizes mucosal protection, elevated the cysteine concentration in the protein fraction of the gastric mucosa. The common factor with the protective agents thus seems to be the blocking of protein SH by binding or oxidation by protective agents. These endogenous SHs may mediate cellular responses to injury.

Effect of acrylonitrile on the rat pituitary: enlargement of Golgi region in prolactin cells, crinophagy in prolactin cells and growth hormone cells

Since it has been shown that acrylonitrile prevents the appearance of spontaneous pituitary adenomas, we have investigated its effect in acute experiments on rat pituitaries by histology, immunocytochemistry, electron microscopy and morphometry; in addition, serum prolactin and growth hormone levels were measured by radioimmunoassay. Electron microscopy of prolactin cells revealed hypertrophy of the Golgi region without significant change in volume densities and diameters of forming and storage granules. In the 24 h group, crinophagy was observed in prolactin cells and growth hormone cells. Corticotrophs, thyrotrophs and gonadotrophs were unaltered. Dilation, congestion and rupture of capillaries, as well as pericapillary and intercellular oedema were evident in the 24 h group. One hour after intravenous acrylonitrile injection, serum prolactin levels were within the normal range, whereas at 24 h, hyperprolactinemia was noted. Serum growth hormone concentrations were unchanged. It can be concluded that acrylonitrile has a complex effect on prolactin cells. Hypertrophy of Golgi complex and hyperprolactinemia may reflect increased prolactin synthesis and release. Since volume densities and diameters of secretory granules in prolactin cells remained unchanged, it appears that newly synthesized prolactin was preferentially released and not the prolactin stored in secretory granules. Crinophagy may be the morphological manifestation of a discrepancy between hormone synthesis and release suggesting increased degradation of unused hormone by lysosomes.

Dose-dependent effects of linear and cyclic somatostatin on ethanol-induced gastric erosions: the role of mast cells and increased vascular permeability in the rat

Somatostatin prevents hemorrhagic gastric erosions produced by ethanol. In this paper we describe studies with linear (reduced) and cyclic (oxidized) synthetic somatostatin-14 in the rat model of ethanol-induced gastric mucosal injury. The linear form of somatostatin was more potent at concentrations of 10(-9) to 10(-8) mol per rat than the cyclic isomere. However, at a concentration of 10(-7) mol per rat i.p. injection of linear somatostatin significantly (P less than 0.01) enhanced gastric erosions caused by the alcohol. The area of hemorrhagic mucosal lesions correlated significantly (r = -0.846) with mast cell depletion in the gastric mucosa of the animals. Increased vascular permeability and mast cell degranulation were also observed after intradermal injection of linear or cyclic somatostatin. The 'cytoprotective' as well as the aggravating potency of linear somatostatin may be connected to gastric mucosal mast cell activity in the rat.

Cysteamine induces duodenal ulcer in the mouse

A new model of duodenal ulcer disease has been developed in the mouse. The ulcers were produced after either oral or subcutaneous administration of cysteamine which has been shown to cause duodenal ulcer in the rat. Cysteamine induced duodenal ulcers in a time- and dose-dependent manner after oral administration. The new mouse model shares many similarities with both the rat model and human ulcer disease. Cysteamine caused a significant increase in gastric acidity and pepsin activity. The mouse can be protected against the cysteamine-induced duodenal ulcer by either the dopamine agonist lergotrile or histamine H2 receptor antagonist cimetidine. This new model of duodenal ulcer disease in the mouse may represent a simple and inexpensive way to screen for new antiulcerogenic drugs.

Alterations in blood vessels during gastric injury and protection

Recent investigations suggest that the mucosal vascular endothelium is not a passive bystander, and that alterations within the blood vessel wall actively participate in the pathogenesis of gastric mucosal injury. We review here our data on rapidly developing vascular injury as detected by monastral blue deposition and increased vascular permeability measured by Evan's blue extravasation in dose- and time-dependent experiments with ethanol, HCl, and NaOH in the rat. In addition, using in vivo microscopy and laser-Doppler velocimetry, we demonstrate circulatory stasis in the superficial capillaries within about 1 min after topical application of damaging agents, and a gradual decrease in blood flow that correlates with the extent of hemorrhagic erosions. Prostaglandins or sulfhydryl agents prevented the circulatory standstill and the development of hemorrhagic mucosal lesions. We conclude that microvascular damage, increased vascular permeability, and capillary stasis precede the development of hemorrhagic mucosal lesions.