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LPS stimulates gastric bicarbonate secretion and prevents gastric injury from acidified ethanol, possibly due to dilution and/or neutralization of this irritant. This study was conducted to determine the time course of LPS-induced alkaline secretion and its relationship with gastroprotection. The role of endogenous prostaglandins in gastroprotection was also examined. When compared to control conscious rats receiving saline, LPS (20 mg/kg IP) for 1, 2, or 3 hours, time dependently increased gastric luminal fluid accumulation (0A ± 0.08 vs. 0.55 ± 0.13, 2.1 ± 0,21, 2.6 ± 0.32 ml) and augmented gastric bicarbonate secretion (0.2 -+ 0.1 vs. 0.4 -+ 0.2, 1.6 ± 0.5, 2.3 ± 0.4 ~tEq). These LPS-induced effects were significantly (p -5/group) different from controls at 2 and 3 hours, but not at 1 hour. Thus, conscious rats received either saline or LPS for 1 hour and then were challenged with 1 ml of the luminal irritant acidified ethanol (150 mM HCI/50% ethanol) for 5 minutes. LPS reduced the magnitude of gastric mncosa involved with macroscopic damage (4.7 ± 1 vs. 15.3 ± 2%, p = 0.01) when analyzed by computerized planimetry. The gastroprotective effect of LPS was in turn negated by administration of the cyclooxygenase inhibitor aspirin (100 mg/kg IP) given 1 hour prior to LPS (14.4±2.6 vs. 4.5±0.1%, p=0.01). In the absence of acidified ethanol and using an enzyme linked immunoassay to measure endogenous prostaglandins, a 1-hour pretreatment with LPS also increased gastric mucosal levels of the prostacyclin metabolite, 6-keto-PGFla (1280±219 vs. 610~-186 pg/mg protein, p = 0.03) but did not enhance prostaglandin E 2 levels (2823 ± 437 vs. 2328 ± 230 pg/mg protein, p = NS) when compared to controls. Aspirin resulted in a 98% reduction in gastric mucosai prostaglandin levels. Consequently, these data suggest that LPSinduced gastroprotection cannot be fully explained by dilution as the protective response is present prior to any significant effect on bicarbonate secretion. Moreover, the mechanism responsible for this action is mediated in part by release of endogenous prostaglandins. This research was funded by NIGMS Grant GM 38529.

Using macroscopic criteria for injury, prostaglandins have been alleged to possess potent antiulcer properties despite meager histologic evidence for this cytoprotective action. This time-sequence study used light, scanning, and transmission electron microscopy to evaluate the effects of 16,16-dimethyl prostaglandin E 2 on gastric mucosal integrity after exposure to 100% ethanol. Macroscopically, virtually complete protection against injury to the glandular mucosa of the in vivo rat stomach was noted in animals receiving 10 μg/kg body wt of prostaglandin subcutaneously before oral ethanol administration when killed at 5, 20, and 60 min after ethanol exposure compared with oral ethanol after saline injection. On light microscopy the length of injured epithelium in prostaglandin/ethanol- and saline/ ethanol-treated tissues was not significantly different at all time periods studied. Although the depth of injury extended into gastric glands in both groups killed at 5 min, the deep pit surface mucus cells in prostaglandin/ethanol mucosa were less damaged and necrotic lesions were virtually absent when compared with saline/ethanol mucosa. At 20 and 60 min, cellular injury could still be identified in prostaglandin/ethanol-treated mucosa but the depth of injury became even less pronounced over time in contrast to mucosa exposed to ethanol without prostaglandin. Scanning electron microscopy and transmission electron microscopy confirmed these differences. Despite the macroscopic findings, these results indicate that prostaglandin does not prevent superficial surface mucus cell necrosis in ethanol-exposed mucosa even though it does spare cells in the pit base. The reduction in damaged cells over time in prostaglandin/ethanol-treated mucosa, in contrast to saline/ethanol-treated mucosa, supports the hypothesis that the reepithelialization of the lamina propria is initiated by spared deep-lying pit cells.

The growth, morphologic, and functional characteristics of eight populations of monolayer culture cells originating from biopsies of human small intestinal mucosa were studied over a period of several months. Epithelial-like cells predominated in the eight cell populations during the first 2 wk of culture, as seen by light and electron microscopy. Some cultures harvested after 10 days contained well preserved and highly organized tissue. These contained enterocytes with a rudimentary brush border and several types of endocrine cells with secretory granules of variable appearance. In addition, these early cultures contained large numbers of loosely arranged epithelial-like cells, which were sometimes attached to one another by junctional complexes. Fibroblasts became the predominant cell type after the second week of culture, at which time ultrastructural changes consistent with dedifferentiation of the epithelial-like cells were observed. The cells also seemed to have a decreased functional capacity with time in that the hormone gastrin was released in diminishing amounts into the medium as the culture period was increased. Additionally, cellular gastrin concentration as well as brush-border enzymatic activity decreased throughout the first 3 wk of culture. These results indicate that epithelial-like cells originating from human intestinal mucosae can be grown for limited periods in monolayer culture. This technique, therefore, may have utility in studying the properties of human intestinal cells for periods up to 2 wk in vitro.

We examined the role of the vagus nerve in mediating the protective effects of subcutaneous 16,16-dimethyl prostaglandin E 2 (16,16-dmPGE 2 ) or of the mild irritant 30% ethanol (topically) against gastric mucosal injury induced by concentrated solutions of ethanol. Anesthetized rats underwent either truncal vagotomy or sham truncal vagotomy and were studied acutely or 7 days later. Under acute conditions, in rats with intact vagi, oral saline followed by 100% ethanol produced severe gastric hemorrhagic and necrotic lesions throughout the glandular gastric mucosa. Oral 30% ethanol or pretreatment with 16,16-dmPGE 2 (5, 10, or 25 μg/kg) before giving oral saline significantly reduced the magnitude of injury when mucosa was subsequently exposed to 100% ethanol. In animals with truncal vagotomy, the protective effect of 16,16-dmPGE 2 or 30% ethanol was not observed. Similar results were noted when animals were studied 7 days after sham or truncal vagotomy. In other studies, the ability of 16,16-dmPGE 2 to prevent gastric injury induced by 50% ethanol or 80 mM aspirin in acid solution (160 mM HCl) with and without prior vagotomy was compared. Although 16,16-dmPGE 2 (5 or 25 μg/kg) pretreatment significantly reduced the degree of gastric damage induced by both agents in the nonvagotomized state, and by aspirin under vagotomized conditions, only partial protection by 16,16-dmPGE 2 against ethanol injury was observed in the vagotomized state. These results suggest that the mechanisms whereby prostaglandins mediate their protective effects against aspirin and ethanol may be different and that the vagus nerve influences the ability of 16,16-dmPGE 2 and of the mild irritant 30% ethanol to prevent alcohol-induced gastric injury in the rat stomach.

Using an in vivo canine chambered stomach preparation, the clearance of [ 14 C]aminopyrine across mucosa when intravenously infused and the backdiffusion of this substance from gastric lumen to mucosa when topically applied to gastric epithelium were evaluated in aspirin-damaged gastric epithelium. In mucosa damaged by either 20 mM or 40 mM aspirin, the recovery of [ 14 C]aminopyrine, when topically mixed with acid (pH = 1.1) perfusate solution, was not significantly different from nondamaged control mucosa. In addition, the degree of "trapping" of this substance from back-diffusion was not different in damaged mucosa from that observed in nondamaged epithelium. In contrast, when [ 14 C]aminopyrine was intravenously infused, its clearance was significantly impaired in aspirindamaged mucosa when compared with control studies, as evidenced by the increased "trapping" of this substance in injured epithelium. These findings indicate that movement of aminopyrine from plasma to gastric lumen is impaired in damaged epithelium, making the aminopyrine clearance technique an unreliable method to accurately measure absolute gastric blood flow in this experimental setting.

Previous reports have demonstrated that the synthetic prostaglandin analogue, 16,16-dimethyl prostaglandin E 2 (dm PGE 2 ), protects the rat gastric mucosa against the damaging effects of a variety of ulcerogenic agents, including alcohol. The effects of dm PGE 2 on alcohol-induced gastric mucosal injury in the dog has not been investigated. Using the canine Heidenhain pouch, the present study examined the action of dm PGE 2 on gastric mucosal damage induced by 15% ethanol, both in the presence and absence of HCl. Ethanol by itself damaged the pouches as evidenced by large net fluxes of Na + and K + into the pouch. The combination of ethanol and 100 mn HCl produced the same effects on Na + and K + and also increased pepsin secretion into the pouch and the loss of H + from the bathing solution. Intravenous injection of dm PGE 2 in the doses 0.01, 0.1, and 1.0 μg per kg, one-half hour before administration of ethanol in acid solution, significantly reduced the net loss of H + from the pouch and the gain of Na + , K + , and pepsin. The most effective doses for protection were 0.1 and 1.0 μg per kg. The increases in Na + and K + efflux elicited by ethanol in the absence of HCl were also significantly reduced by dm PGE 2 . It is concluded that dm PGE 2 effectively protects the canine gastric mucosa against the damaging effects of alcohol and that this protection is dose-related. Although the mechanism underlying this protection is not apparent from this study, it appears to be independent of inhibition of acid secretion because equal protection against ethanol was observed both in the presence and absence of HCl.

This study compared the ability of topical 16,16-dimethyl prostaglandin E 2 in a dose range of 0.3–3.0 μg/ml to prevent aspirin-induced injury in the canine stomach under both in vivo and in vitro conditions. For in vitro studies, isolated strips of oxyntic mucosa were exposed to 10 or 20 mM aspirin (ASA) at pH 1–4, with and without treatment with 16,16-dimethyl prostaglandin E 2 . For in vivo experiments, a portion of the oxyntic stomach was mounted between the rings of a Lucite chamber, with splenic vessels intact, such that the mucosa was divided into halves. Both sides were exposed to 20 mM ASA at pH 1 or 2, and one side also received concomitant treatment with 16,16-dimethyl prostaglandin E 2 . After ASA exposure, tissue samples were prepared for quantitative microscopic analysis of the degree of injury. Under both experimental conditions, the magnitude of gastric injury by ASA was pH-related, being most pronounced at pH 1; this damage was worse under in vitro conditions, and both concentrations of ASA were equally damaging in this setting. 16,16-Dimethyl prostaglandin E 2 failed to prevent ASA injury in vitro at any pH and ASA concentration tested, but markedly reduced the magnitude of injury in vivo. The most effective protective dose of 16,16-dimethyl prostaglandin E 2 under in vivo conditions was 1.0 μg/ml. The diminished tolerance to ASA damage in vitro when compared with in vivo, and the inability of 16,16-dimethyl prostaglandin E 2 to prevent these damaging effects in vitro, underscores the probable crucial role for blood flow, and possibly neural innervation, in mediating the protective effects of prostaglandins.