Effect of estrogen on visceral sensory function in a non-inflammatory colonic hypersensitivity rat model.

BACKGROUND: Increased prevalence of functional gastrointestinal disorders in women and perimenstrually accentuated symptoms imply that sexual hormones play a crucial role in the pathogenesis of such syndromes. The aim of this study was to analyze the selective effect of estrogen on visceral sensitivity in gonadectomized female and male Lewis rats with or without prior treatment with butyrate enemas. METHODS: Following ovariectomy (OVX) or orchiectomy (ORX) estradiol pellets (E2-P) or sham pellets (Sham-P) were implanted. After treatment with butyrate (BUT) or saline (NaCl) enemas, colorectal distensions (CRD) were performed and the visceromotor reflex (VMR) to CRD was measured by electromyography. KEY RESULTS: Gender did not influence VMR to CRD in gonadectomized animals. VMR in E2-P animals compared to Sham-P animals was increased (635 ± 32 µVs vs 470 ± 39 µVs; p = 0.002). Overall, instillation of butyrate enemas did not influence VMR to CRD. A comparison of CRD clusters showed that butyrate enemas in the E2-P animals resulted in a significant sensitization in both OVX and ORX animals. In female rats, sensitization was also caused by estrogen substitution alone. CONCLUSION & INFERENCES: In our animal model, estrogen is a strong factor for an increase in visceral sensory function. Surprisingly, the treatment with butyrate alone did not evoke a general rise in VMR to CRD. Rats treated with butyrate enemas and under selective estrogen substitution developed visceral sensitization during the series of CRDs.

Effects of the Tibetan herbal formula Padma Lax on visceral nociception and contractility of longitudinal smooth muscle in a rat model.

BACKGROUND: The high prevalence of functional bowel disorders among the general population contrasts with the limited number of pharmacological treatment options for this condition. This has led to an interest for alternative therapeutic approaches. Padma Lax is an herbal laxative on the basis of Tibetan formulas. Our aim is to examine the effect of Padma Lax on visceral nociception in vivo and (B) on contractile activity of longitudinal smooth muscle of the lower gut in vitro and ex vivo. METHODS: (A) Visceral sensory function in response to colorectal distension was assessed by abdominal wall electromyography in male Wistar rats pretreated with Padma Lax. (B) Effects of Padma Lax on contractility of gut smooth muscles were studied both in vitro with superfusion of the agent and ex vivo following oral administration of the preparation. Activities were measured as area under the curve. KEY RESULTS: (A) For visceral sensitivity, no differences were observed between the Padma Lax and the control group. (B) Proximal colon muscle strips of the Padma Lax pretreated group showed significantly lower spontaneous contractility ex vivo than controls. Cholinergic procontractile stimulation was reduced in Padma Lax pretreated group and in colon strips of naive rats when Padma Lax was superfused in vitro (all P < 0.05). CONCLUSION & INFERENCES: Cholinergic mechanisms appear to be important in the modulation of rat proximal colon contractility of orally and directly applied Padma Lax. These findings help elucidate a potential mechanism of action of this herbal remedy which has undergone clinical testing in patients with constipation predominant irritable bowel syndrome.

Amelioration of murine colitis by feeding a solution of lysed Escherichia coli.

BACKGROUND: Immune reactivity towards the bacterial intestinal flora plays an important part in the pathogenesis of inflammatory bowel disease. Disease activity can be positively influenced by the administration of living probiotic bacteria. We investigated the effect of soluble bacterial antigens extracted from Escherichia coli (strain Laves) on the disease activity of murine colitis. METHODS: C3H.IL-10-/- and BALB/c mice with dextran sulphate sodium-induced colitis were treated with either a bacterial lysate from E. coli or with a placebo. Mice were monitored and inflammation was assessed by histological scoring, analysis of fecal IL-1beta and measurement of cytokine production by ELISA. T cell proliferation was quantified by 3H-thymidine incorporation. RESULTS: Clinically and histologically, bacterial-lysate-treated mice revealed significantly (P < 0.05) fewer signs of colitis than placebo-treated mice. Fecal IL-1beta and mucosal TNF-alpha and IFN-gamma concentrations were significantly lower (P < 0.05) in verum-treated mice than in the placebo group. Furthermore, lymphocyte proliferation after stimulation with lipopolysaccharide or caecal bacterial antigen was significantly (P < 0.05) reduced in verum-treated mice. CONCLUSION: The use of E. coli lysate is effective in the amelioration of murine colitis. This effect may be due to a decreased Th1 reaction and to an induction of tolerance against bacterial antigens.

Comparison of the effect of the antacid Rennie versus low-dose H2-receptor antagonists (ranitidine, famotidine) on intragastric acidity.

BACKGROUND: Symptoms of functional dyspepsia are common and patients often self-medicate with antacids, or with low-dose H2-antagonists which are available as over-the-counter medications. To date, there has been limited information available comparing the effects on intragastric acidity of these two types of over-the-counter medication. Therefore we studied the effect of the antacid Rennie and two H2-antagonists on the intragastric pH of fasting volunteers. METHODS: Sixteen healthy, fasting volunteers were randomized into a double-blind, placebo-controlled, four-way crossover study comparing Rennie (calcium-magnesium carbonate) 1360 mg, ranitidine 75 mg, famotidine 10 mg and placebo. Their effect on gastric pH was monitored by a 4-h gastric pH-metry. The primary efficacy parameter was the time lag before an intragastric pH > 3.0 was reached after drug administration. RESULTS: The median time lag before pH > 3.0 was reached after drug administration was 5.8 min for Rennie, 64.9 min for ranitidine, 70.1 min for famotidine and 240.0 min for placebo. The percentage of time with values of pH > 3.0 was 10.4% for Rennie, 61.4% for ranitidine, 56.6% for famotidine and 1.4% for placebo. CONCLUSION: The onset of action in fasting volunteers was significantly faster with the antacid than with the two H2-antagonists. The duration of action was significantly longer with an H2-antagonist than with the antacid. This suggests that the two products should be used for different indications: antacids are superior for rapid pain relief, whereas H2-antagonists might be better for symptom prophylaxis--for example for nocturnal dyspepsia.

Effects of inhibition of prostaglandin endoperoxide synthase-2 in chronic gastro-intestinal ulcer models in rats.

1. In the stomach, prostaglandins protect the gastric mucosa against injuries. One rate-limiting step in prostaglandin synthesis is mediated by prostaglandin endoperoxide synthase (PGHS), the target enzyme of non-steroidal anti-inflammatory drugs (NSAIDs). Two isoforms of PGHS exist: a constitutive (PGHS-1) and an inducible (PGHS-2) enzyme. PGHS-1 is the major source of gastric prostaglandins under physiological conditions. Inhibition of prostaglandin synthesis by traditional NSAIDs such as indomethacin and diclofenac which non-selectively inhibit both PGHS-1 and PGHS-2, causes gastric and intestinal ulceration and delays gastric ulcer healing in chronic models. It has been shown that selective PGHS-2 inhibitors such as L-745,337 (5-methanesulphonamide-6-(2,4-difluorothio-phenyl)-1-inda none) are not ulcerogenic and do not inhibit gastro-intestinal prostaglandin synthesis. However, minimal information is available on the long-term effects of PGHS-2 inhibitors on the healing of previously established gastric injuries. We assessed the cellular localization and expression of PGHS-1 and PGHS-2 during gastric ulcer healing and assessed the effects of L-745,337 on previously established cryoulcers in the rat gastric stomach. 2. PGHS-1 and PGHS-2 were located and quantified by immunohistochemistry during experimental gastric ulcer healing. PGHS-2 immunoreactivity was only negligible in the normal gastric wall, but after gastric ulcerations, it was strongly detected in monocytes, macrophages, fibroblasts and endothelial cells below and between the regenerative glands. PGHS-1 immunoreactivity detected in normal gastric mucosa, disappeared after gastric ulceration in the mucosa adjacent to the ulcer crater. However, it reappeared in the regenerative glands from day 5 onwards. Thus, PGHS-1 and PGHS-2 were located at different sites and their maximal expression followed a different time-sequence. 3. We assessed the effects of L-745,337, indomethacin and diclofenac on gastric ulcer healing and histological healing parameters in rats. L-745,337, indomethacin and diclofenac dose-dependently decreased the healing of gastric ulcers. L-745,337, indomethacin and diclofenac decreased epithelial cell proliferation in the ulcer margin and microvessel density in the ulcer bed on day 8 and increased the thickness of the granulation tissue below the ulcer crater and the gap between both edges of the muscularis mucosae on day 15. Indomethacin and diclofenac, but not L-745,337, decreased synthesis of 6-keto-PGF1alpha and PGE2 in tissue fragments from the stomach and terminal ileum and decreased platelet thromboxane B2 synthesis in clotting whole blood. 4. Dose-response curves for the inhibition of chronic gastric ulcer healing by L-745,337 (administered twice daily intragastrically) showed an ID50 value of 1.7 mg (4.3 micromol) kg(-1). Dose-response curves for the inhibition of PGE2 synthesis in inflammatory exudates in the acute carrageenin sponge rat model, showed ID50 values of 1.1 mg (3.1 micromol) kg(-1) and 1.3 (3.3 micromol) mg kg(-1) for indomethacin and L-745,337, respectively. Thus, inhibition of chronic gastric ulcer healing by L-745,337 occurs within a potentially therapeutic dose-range. 5. In summary, PGHS-2 is markedly accumulated after gastric ulceration in monocytes, macrophages, fibroblasts and endothelial cells in regions of maximal repair activity. Selective inhibition of PGHS-2 by L-745,337 delayed gastric ulcer healing though interference with epithelial cell proliferation, angiogenesis and maturation of granulation tissue in a potentially therapeutic dose range. PGHS-2-derived prostaglandins seem to have an important role in gastric ulcer healing.

Roles of hepatocyte growth factor and its receptor Met during gastric ulcer healing in rats.

BACKGROUND & AIMS: It is unclear which growth factors are primarily responsible for stimulating gastric ulcer healing. The roles of hepatocyte growth factor (HGF) and Met/HGF receptor during gastric ulcer healing were studied in rats. METHODS: HGF and Met/HGF receptor were located and quantified by in situ hybridization and immunohistochemistry during experimental gastric ulcer healing. The in vivo effects of exogenous recombinant human HGF on cell proliferation and ulcer healing were assessed and compared with those of placebo and omeprazole treatment. RESULTS: Compared with intact oxyntic mucosa, messenger RNA (mRNA) of HGF and met was substantially greater in the ulcerated region on days 3 and 15. HGF mRNA was located in stromal cells between the regenerative glands and in the arterial vessels of submucosal tissue, whereas met mRNA was located in the epithelial cells of the regenerative glands. After cryoinjury, immunoreactivity for the Met/HGF receptor was absent on day 3, reappeared on day 8, and was overexpressed on day 15. Exogenous recombinant human HGF had no effect on the ulcer healing parameters over days 3-8, but it did increase epithelial cell proliferation in the ulcer margin over days 8-15. CONCLUSIONS: These data suggest that HGF mediates specific tissue interactions between mesenchyme and epithelia during gastric ulcer healing.

Influence of acid and angiogenesis on kinetics of gastric ulcer healing in rats: interaction with indomethacin.

Indomethacin delays healing of experimental gastric ulcers. We investigated whether inhibition of gastric acid secretion by omeprazole or stimulation of angiogenesis by basic fibroblast growth factor (bFGF) may reverse this delay. Rats with gastric ulcers induced by cryoprobe were treated subcutaneously with either placebo, indomethacin (2 x 0.5 mg/kg), bFGF (2 x 100 micrograms/kg), omeprazole (1 x 40 mumol/kg), indomethacin plus omeprazole, or indomethacin plus bFGF given daily for 8, 10, 15, and 22 days. Ulcer size, epithelial cell proliferation, angiogenesis, and maturation of granulation tissue were sequentially quantified. Omeprazole significantly accelerated ulcer healing in an early phase (days 3-8). In contrast, bFGF accelerated healing in a late phase (days 10-15). Indomethacin significantly delayed ulcer healing in late phase and decreased prostaglandin generation, cell proliferation, angiogenesis, and maturation of granulation tissue. Despite stimulation of angiogenesis, bFGF did not reverse indomethacin-induced delay in ulcer healing. In contrast, omeprazole reversed indomethacin-induced effects on angiogenesis, cell proliferation, maturation of granulation tissue, and ulcer healing rate.

Antacid provides better restoration of glandular structures within the gastric ulcer scar than omeprazole.

Mucosa of healed gastric ulcers displays histological abnormalities that are possibly the basis of ulcer recurrence. The influence of antacid and omeprazole treatment was studied on the quality of ulcer healing. Sixty four rats with gastric cryoulcers were treated daily either with placebo, antacid, omeprazole, or antacid plus omeprazole. Ulcer size was measured three times per week with a novel video endoscopic method. Prostaglandin generation (day 6), cell proliferation (day 8 and 15), height and cell composition of ulcer margin (day 8), and mucosal scar (day 15) were quantitatively assessed. Antacid, omeprazole, and antacid plus omeprazole significantly accelerated ulcer healing predominantly during days 3-8. Compared with placebo, the height of ulcer margin and mucosal ulcer scar was significantly increased in antacid (+7 and +9% respectively) and significantly decreased in omeprazole (-33 and -22% respectively) and antacid plus omeprazole (-26 and -18% respectively) treated rats. The number of bromodeoxyuridine labelled cells (+42%, day 8), epithelial cell mass (+42%, day 15), and the ratios of epithelial cells/connective tissue (+73%, day 15) and epithelial cells/gland lumen (+100%, day 15) were significantly increased in antacid treated rats. In conclusion, both antacid and omeprazole accelerate ulcer healing but antacid provides a better quality of healing. This advantage is lost by cotreatment with omeprazole.

Cholecystokinin type B receptor antagonist PD-136,450 is a partial secretory agonist in the stomach and a full agonist in the pancreas of the rat.

Gastrin (cholecystokinin type B (CCK-B)) receptor antagonists may help to elucidate the physiological role of gastrin, have therapeutic potential as acid antisecretory drugs, and may be of use as adjuvant therapy for gastrin sensitive tumours. In binding studies, the gastrin receptor antagonist PD-136,450 had at least 1000 fold greater affinity for gastrin (CCK-B) than CCK-A receptors. In this study the biological activity of PD-136,450 was evaluated in conscious and anaesthetised rats. PD-136,450 antagonised gastrin stimulated acid secretion after subcutaneous (IC50: 0.28 mumol/kg; conscious rats) and intravenous (IC50: 0.17 mumol/kg; anaesthetised rats) administration. In basal secreting fistula animals, the compound stimulated acid output to 30 (5)% of the maximal response to gastrin. Stimulant activity was not caused by gastrin release. As an agonist PD-136,450 was about 350 times less potent than gastrin-17 on a molar basis. In addition, PD-136,450 was a powerful agonist of pancreatic secretion in anaesthetised rats. The specific gastrin antagonist L-365,260 inhibited the (partial) agonist activity of PD-136,450 in the stomach and the specific CCK-A receptor antagonist L-364,718 inhibited the agonist activity of PD-136,450 in the pancreas. It is concluded that the agonist effect of PD-136,450 is mediated via interaction with the gastrin (CCK-B) receptor in the stomach and the CCK-A receptor in the pancreas.

Interleukin-1 and experimental gastric ulcer healing in the rat.

The involvement of inflammation in peptic ulcer development and healing attracts growing interest. Since lymphokines, in particular interleukin-1 (IL-1), as ubiquitous mediators of inflammation are currently intensively studied in the gastrointestinal tract, we assessed the effect of this cytokine as well as that of a specific IL-1 release inhibitor (IX 207-887 (IX)) on development and healing of experimental gastric ulcers. After a single dose of IL-1, 4 micrograms/kg, i. p., basal acid secretion was almost completely inhibited for 4 hours in conscious chronic gastric fistula rats. In a first study, following induction of a 7 mm wide cryo-ulcer in the gastric corpus, three groups of 24 rats were treated either with a non-acid inhibitory dose of IL-1 (0.4 microgram/kg) or with an antisecretory regimen (4 micrograms/kg) b.i.d. or saline control. Ulcer size did not differ from that of control animals, neither after 24h nor 7 days. Similarly, IX applied daily (20 mg/kg/s.c) from 5 days before ulcer induction and continued thereafter for 15 days had no effect on ulcer development or healing. Despite its anti-inflammatory property IX produced no macroscopically visible damage on the gastric or intestinal mucosa and may therefore offer a higher safety profile within the gastrointestinal tract than conventional non-steroidal anti-inflammatory drugs.

Effect of acute and chronic acid suppression on plasma gastrin release in the rat.

The mechanisms by which administration of the H+,K(+)-ATPase inhibitor B 831-78 or intragastric perfusion with NaHCO3 induces plasma gastrin release were studied in the rat. Experiments were performed after a washout of residual intragastric contents in fasted animals provided with chronic gastric fistulae. Acute and chronic administration of B 831-78 elevated plasma gastrin dose-dependently up to 5-6 times above control levels, while the increase was only twofold with intragastric NaHCO3 infusion despite similar neutralization of gastric acidity. The profound hypergastrinaemia induced by the H+,K(+)-ATPase inhibitor, after both acute and chronic treatment, was completely prevented or reversed by intragastric perfusion with physiological amounts of acid (0.15 N HCl, 2.5 ml/h). The hypergastrinaemia was, however, largely resistant to high doses of atropine (4.3 mumol/kg) and of the M1 selective muscarinic antagonist telenzepine (10 mumol/kg). In contrast, the modest increase in plasma gastrin induced by gastric perfusion with NaHCO3 was completely suppressed by the high atropine dose and was attenuated by small doses of atropine or telenzepine (0.01 mumol/kg and 1 mumol/kg). These results demonstrate that, in the rat, blockade of the H+,K(+)-ATPase can potently induce gastrin release in the absence of a meal. Moreover, they suggest that interruption of the negative feedback between acid and gastrin release is the main mechanism through which this class of drugs releases gastrin in the rat. Since a similar degree of gastrin release cannot be achieved by alkalinization of gastric contents, additional hormonal or neural regulatory factors may contribute to the drug-induced hypergastrinaemia.