Biomedical subjects

F Guarner

Publications and source records attributed to F Guarner.

At least 37 records · Page 2Linked to original sources

PubMed1996

Induction of chronic pancreatic disease by trinitrobenzene sulfonic acid infusion into rat pancreatic ducts.

Despite being a common disease in humans, little is known about the etiopathogenesis of and effective therapeutic approaches to chronic pancreatitis, due mainly to the fact that few simple animal models suitable to study inflammatory and fibrogenetic processes have been described in the pancreas. Trinitrobenzene sulfonic acid (TNBS) induces chronic colitis and cholangitis in the rat. We hypothesized that TNBS instillation into the pancreatic ducts could also result in the development of a chronic pancreatic disease. The biliopancreatic duct of rats was cannulated and tied close to the liver. TNBS [0.4 ml of 2% TNBS in phosphate-buffered saline (PBS)-10% ethanol, pH 8] was infused into the pancreas under a continuous controlled-pressure system. Control rats underwent the same procedure using vehicle only. Pathology assessment of TNBS-treated rats examined at 48 h was consistent with severe acute necrotizing pancreatitis, having a morality rate of 31% and serum amylase activity of 37.4 +/- 8.8 U/ml at 24 h and 13.3 +/- 1.7 U/ml at 48 h (p < 0.01 for both time points compared to PBS/ethanol-treated rats). Groups of 10 rats each were killed at 3, 4, and 6 week after the surgical procedure. Morphological examination revealed changes mimicking features of chronic pancreatitis in humans in 80% (32 of 40) of TNBS-treated rats, consisting in various degrees of periductal and lobular fibrosis, duct stenosis, patchy acute and chronic inflammatory cell infiltrates, and signs of gland atrophy. Animals developing chronic disease had a weight gain rate significantly lower than that of control rats. Serum amylase, fasting glucose, and a glucose tolerance test were not different in diseased or control rats. In conclusion, we were able to induce chronic fibrogenetic inflammatory disease in the pancreas after a single pulse instillation of TNBS into the pancreatic ducts. This might be a useful animal model to study the pathophysiology of inflammatory, fibrogenetic, and reparative processes in pancreatic tissue.

Amylases↗

PubMed1996

Bile acid induced colonic irritation stimulates intracolonic nitric oxide release in humans.

AIM: To measure the intracolonic release of nitric oxide end products (nitrates plus nitrites) and eicosanoids in response to intraluminal irritation with deoxycholic acid (DCA). PATIENTS: Seven patients with irritable bowel syndrome. METHODS: The left colon was perfused with a solution with or without 3 mM deoxycholic acid. Aspirates were assayed for eicosanoids by specific radioimmuno-assay, and for nitrates plus nitrites by the Griess reaction. To confirm that stimulated colonic mucosa can produce nitric oxide (NO), ancillary studies were performed in vitro using samples of normal mucosa obtained from five surgically resected colons. Samples were incubated for 30 minutes in Kreb's solution, 3 mM DCA or DCA with 1 mM L-nitro-arginine-methyl-ester (L-NAME) to inhibit the NO synthase. Finally, NO synthase activity was measured in five samples of human colonic mucosa. RESULTS: Intracolonic release of nitrates plus nitrites was basally undetectable in six of seven patients. Bile acid considerably increased the release of prostaglandin E2 and nitrates plus nitrites (p < 0.01). By contrast, no increase in thromboxane and leukotriene was seen. In vitro mucosal incubation with DCA increased the production of NO synthase products, which was blocked by L-NAME. Activity of Ca+2 independent NO synthase was detectable in four of five samples of human colonic mucosa. CONCLUSION: The human colonic mucosa responds to bile acid induced irritation by a surge in NO generation via NO synthase.

Adolescent↗

PubMed1996

Toxic dilatation of colon in a rat model of colitis is linked to an inducible form of nitric oxide synthase.

The contribution of nitric oxide (NO) to the altered colonic contractility of acute colitis was investigated in the 2,4,6-trinitroben-zenesulfonic acid model. NO synthase was measured in colonic tissue; the effects of NO synthase inhibition on colonic contractility were studied in vitro and in vivo. Inducible NO synthase was not detected in normal colons, whereas inflamed colons showed high activity. Acute inflammation was associated with enlarged colonic perimeter. NO synthase inhibitors or selective inhibitors of the inducible enzyme prevented colonic dilatation. In vitro, contractile responses to KCl were lower in muscle from colitic than control rats. After NO synthase inhibition, however, no difference was observed between colitic and control muscle contractility. In vivo, intracolonic pressure was lower in colitic than in control rats. Selective inhibition of inducible NO synthase increased intracolonic pressure in colitic but not in control rats. In conclusion, NO generation by inducible enzymes impairs smooth muscle contractility in colitis and may be involved in the pathogenesis of toxic dilatation of the colon.

Animals↗

PubMed1996

Bacterial peptides enhance inflammatory activity in a rat model of colitis.

Bacterial products released within the gut lumen may alter the course of inflammatory bowel lesions. The effect of intraluminal N-formyl methionyl-leucyl-phenylalanine on mucosal release of inflammatory mediators was investigated in normal and colitis rats (at 1 and 7 days after induction of colitis by trinitrobenzenesulfonic acid). Under anesthesia, the distal colon was perfused using an isosmotic solution with or without synthetic N-formyl methionyl-leucyl-phenylalanine (100 nmol/ml). Effluents were assayed for eicosanoid (PGE2, TXB2 and LTB4) concentration. Myeloperoxidase activity was measured in colonic wall homogenates. In normal rats, peptide perfusion did not change mucosal release of PGE2, TXB2 and LTB4. Colitic rats showed high baseline release of eicosanoids. The peptide did not further increase PGE2 and TXB2 release, but significantly stimulated LTB4 both on days 1 and 7 after induction of colitis. Rats with high myeloperoxidase activity in the colonic wall showed a marked LTB4 response to the peptide. Finally, peptide perfusion increased tissue myeloperoxidase activity in colitis at day 7 but not in colitis at day 1 or in normal rats. In conclusion, bacterial products may activate inflammation. This mechanism of lumen-wall interaction might be involved in the perpetuation of inflammatory lesions of the colonic mucosa.

Animals↗

PubMed1995

Nitric oxide modulates pancreatic basal secretion and response to cerulein in the rat: effects in acute pancreatitis.

BACKGROUND/AIMS: Nitric oxide synthase activity is detected in the pancreas, but the role of NO on pancreatic function has not been fully characterized. The aim of this study was to evaluate the role of NO in normal and diseased pancreatic function. METHODS: Amylase and NO secretion were measured in vivo in rats and in vitro in dispersed acini, with and without NO synthesis blockade, by NG-nitro-L-arginine methyl ester (L-NAME). Rats were subjected to cerulein-induced pancreatitis, and the effects of L-NAME or NO donors were assessed. RESULTS: L-NAME reduced amylase output to 60% of basal. This effect was reversed by L-arginine. The secretory response to optimal doses of cerulein induced a poor amylase secretion and a marked release of NO. High doses of cerulein in combination with L-NAME inhibited NO formation and amylase secretion. In dispersed acini, supramaximal cerulein concentrations induced NO release, but the amylase dose-response curve was not modified by NO inhibition. In acute pancreatitis, L-NAME increased amylasemia and tissue myeloperoxidase activities, whereas NO donors reduced amylasemia, lipasemia, and the histological damage score. CONCLUSIONS: The L-arginine/NO pathway facilitates basal and stimulated pancreatic secretion in vivo. NO donor drugs may improve the course of acute pancreatitis.

Acute Disease↗

PubMed1995

Induction of nitric oxide synthase in colonic smooth muscle from patients with toxic megacolon.

BACKGROUND & AIMS: Colonic inflammation may lead to motility disturbances, including severe atony. Nitric oxide is released by inflamed tissue and induces smooth muscle relaxation. The aim of this study was to analyze NO generation pathways in colonic tissue from patients who had ulcerative colitis with or without toxic megacolon and in tumor-free samples from patients with colonic neoplasm. METHODS: Enzymatic activity was determined by transformation of [14C]arginine to [14C]citrulline in mucosa and muscular layer samples. Immunostaining of tissue sections with antibody against inducible NO synthase was investigated. The effects of endotoxin on NO synthase activity was tested in muscle strips from human colon. RESULTS: Ca(2+)-independent NO synthase was undetectable or very low in muscularis propria from tumor and colitis controls. In contrast, specimens from patients with toxic megacolon had high activity (P < 0.05). Positive immunostaining for inducible NO synthase was found in muscular layers from patients with megacolon but not in tumor and colitis controls. Finally, endotoxin induced Ca(2+)-independent NO synthase activity in colonic muscle. CONCLUSIONS: Toxic megacolon is associated with the appearance of inducible NO synthase in the colonic muscularis propria. Local generation of excessive amounts of NO may be responsible for the colonic dilatation that is the hallmark of this syndrome.

Adult↗

PubMed1995

Induction of chronic cholangitis in the rat by trinitrobenzenesulfonic acid.

We investigated the effects of the hapten trinitrobenzenesulfonic acid instilled into the rat biliary tree. The study included three groups of animals that received a single intracholedochal injection of either saline, 10% ethanol or 10 mg trinitrobenzenesulfonic acid dissolved in 10% ethanol. A fourth group of rats was subjected to common bile duct ligation and was used as control for biliary obstruction. Liver and biliary tract dysfunction was assessed 1, 10, 20 and 30 days after treatment by serum aspartate aminotransferase, alkaline phosphatase and bilirubin, and by histopathological examination of liver slices. By day 10, saline- or ethanol-treated rats did not show changes in the biochemical parameters, and light microscopy revealed no alterations. In contrast, rats treated with trinitrobenzenesulfonic acid showed significant increases in all serum markers throughout the study period. Inflammatory cell infiltrates were seen in portal areas and around bile ducts, indicating pericholangitis. Some rats presented with dilatation of extrahepatic biliary ducts; ductal proliferation and thin porto-portal fibrotic septa were observed in these cases. Bile duct ligation also induced ductal proliferation and fibrosis in all cases, but pericholangitis was not prominent. Retrograde cholangiograms in trinitrobenzenesulfonic acid rats showed distortion of the intra- and extrahepatic biliary tree. In conclusion, chronic cholangitis may be consistently induced in rats by a single intracholedochal administration of trinitrobenzenesulfonic acid.

Alkaline Phosphatase↗

PubMed1995

Intracolonic release in vivo of interleukin-1 beta in chronic ulcerative colitis.

1. To investigate the role of interleukin-1 beta in chronic ulcerative colitis, we quantified interleukin-1 beta steady-state release into the colonic lumen. 2. We studied 26 patients with untreated chronic ulcerative colitis and seven patients with irritable bowel syndrome who served as disease controls. In seven ulcerative colitis patients, the disease was inactive and in 19 it was mild to moderately active, according to clinical and colonoscopic criteria. Seven patients with active colitis were studied before and after 4 weeks of treatment with oral 5-aminosalicylic acid. 3. Colonic perfusions were performed using a double-lumen technique. An isotonic solution was continuously infused 50 cm from the anal verge at 5 ml/min, and was recovered 30 cm distally by siphonage. Interleukin-1 beta was measured by ELISA, polymorphonuclear elastase by immunoactivation and leukotriene B4 by specific RIA. 4. All control patients and five out of seven patients with inactive colitis had undetectable interleukin-1 beta release. In active colitis, the release of interleukin-1 beta was detected in 17 out of 19 patients (median 500 pg/min, interquartiles 270-1582 pg/min, P < 0.01 compared with control subjects and patients with inactive colitis). Elastase and leukotriene B4 release were also significantly increased in active colitis compared with inactive colitis and controls. Leukotriene B4 release was similar in inactive colitis and controls, whereas elastase release was higher in inactive colitis than in controls. Five out of seven patients with colitis improved after treatment with 5-aminosalicylic acid. In all responder patients, interleukin-1 beta became undetectable or declined. 5. Our results demonstrate under conditions in vivo that active colitis is associated with enhanced interleukin-1 beta release into the colonic lumen whereas such release does not occur in remission, supporting the concept that ulcerative colitis flare-ups involve increased interleukin-1 beta production.

Adolescent↗

PubMed1995

Effects of thromboxane synthase inhibition on in vivo release of inflammatory mediators in chronic ulcerative colitis.

OBJECTIVE: To evaluate the effects of a thromboxane inhibitor on the production of eicosanoids by the colonic mucosa of patients with chronic ulcerative colitis. PATIENTS AND METHODS: Fourteen patients with active left-sided ulcerative colitis were divided into in two treatment groups. Seven patients received oral ridogrel (300 mg twice daily) and seven 5-aminosalicylic acid (5-ASA; 1 g twice daily) for 4 weeks. Intracolonic eicosanoid and elastase release were measured using a colonic double-lumen perfusion technique. An isotonic solution was infused 50 cm from the anal verge at the rate of 5 ml/min, and recovered by siphonage 30 cm distally. Effluents were assayed for thromboxane B2 (TXB2), prostaglandin E2 (PGE2), and leukotriene B4 (LTB4) by radioimmunoassay (RIA), and for polymorphonuclear elastase by immunoactivation. Clinical and colonoscopic criteria were used to determine activity before and after treatment. RESULTS: Four of the seven patients in the ridogrel group and five of the seven in the 5-ASA group showed clinical and colonoscopic improvement. Intraluminal elastase release decreased in every responding patient in the 5-ASA group (P < 0.05) and in three out of seven responders in the ridogrel group. Basal eicosanoid release was similar in both groups. In the responders, 5-ASA significantly reduced the release of the three eicosanoids (P < 0.05). Ridogrel reduced the release of TXB2 to 31% of basal levels (P < 0.01) but the release of PGE2 and LTB4 was not affected. CONCLUSIONS: These results suggest that ridogrel is an oral active selective inhibitor of thromboxane synthetase, which modifies the pattern of colonic eicosanoid generation in patients with chronic ulcerative colitis. Oral ridogrel may be a useful treatment for patients with non-severe ulcerative colitis, although specific indications require further studies.

Adult↗

PubMed1994

Phosphatidylcholines as mediators of adaptive cytoprotection of the rat duodenum.

BACKGROUND/AIMS: Surfactant phospholipids impede diffusion of acid through the gastric mucus, but their relevance in the defense of the duodenum against luminal acid is not known. METHODS: Duodenal resistance to acid was tested in anesthetized rats by instillation of HCl using a tube implanted in the proximal duodenum. The effects of a detergent (Brij 35; Sigma, St. Louis, MO) and a lipid mixture flushed through the luminal surface on duodenal resistance to acid were studied. The lipid content in the mucus and the effects of acid, prostaglandins, and indomethacin on the lipid layer were also analyzed. RESULTS: Instillation of 100 mumol HCl or 5 micrograms/kg 16,16-dimethyl prostaglandin E2 increased resistance to acid, preventing duodenal lesions induced by 500 mumol HCl. However, 100 mumol HCl or 16,16-dimethyl prostaglandin E2 did not prevent lesions induced by 500 mumol HCl in rats undergoing perfusions with 5% Brij 35. Indomethacin suppressed acid-induced protection. A mixture of tripalmitin and dipalmitoyl-phosphatidylcholine protected against 500 mumol HCl, and the effect was also observed in rats receiving indomethacin. Finally, 100 mumol HCl increased the phosphatidylcholine content in the duodenal mucus but not in rats receiving 5% Brij 35 or indomethacin. CONCLUSIONS: Surface-active phospholipids are critical for adaptive cytoprotection to acid in the rat duodenum.

16,16-Dimethylprostaglandin E2↗

PubMed1994

Selective gastric hypersensitivity and reflex hyporeactivity in functional dyspepsia.

BACKGROUND/AIMS: We have previously shown that patients with functional dyspepsia are hypersensitive to gastric distention. The aim of this study was to establish whether this sensory disturbance was confined to the stomach and whether it was associated with gut reflex dysfunction. METHODS: In 10 selected patients with dyspepsia and 12 healthy controls, perception and gut reflex responses to gastric distention, duodenal distention, and somatic stimulation were measured. Standardized distentions at fixed pressures were performed by gastric and duodenal barostats. Perception was scored by a detailed symptom questionnaire; gut reflex responses were measured as isobaric volume changes by each barostat. Somatic transcutaneous electrical nerve stimulation was produced on the hand. Individual stimuli (2-minute duration) were randomly applied at 10-minute intervals in stepwise increments in search of the respective threshold for discomfort. RESULTS: Patients with dyspepsia had gastric hypersensitivity to distention (discomfort threshold at 6.4 +/- 0.4 mm Hg vs. 8.3 +/- 0.6 mm Hg in controls; mean +/- SE; P < 0.05), whereas duodenal and somatic sensitivity was normal. Furthermore, patients with dyspepsia explicitly recognized their clinical symptoms in all gastric but only in 58% +/- 12% of the duodenal distention trials. In addition, patients with dyspepsia showed defective gastric relaxatory responses to duodenal distention (68 +/- 30 mL gastric expansion vs. 239 +/- 12 mL in controls; P < 0.05). CONCLUSIONS: Patients with dyspepsia are selectively hypersensitive to gastric distention; this sensory dysfunction is associated with impaired reflex reactivity of the stomach.

Adult↗

PubMed1994

Intraluminal colonic release of immunoreactive tumour necrosis factor in chronic ulcerative colitis.

1. Tumour necrosis factor is a proinflammatory macrophage-derived polypeptide cytokine. Its participation in disease processes has been usually inferred from data obtained from experiments in vitro or from measurements of its plasma circulating levels. To investigate its role in chronic ulcerative colitis, we have quantified in vivo the steady-state release of tumour necrosis factor into the colonic lumen. 2. We studied 19 patients with untreated active ulcerative colitis and seven patients with irritable bowel syndrome as controls. A group of seven patients with active ulcerative colitis were studied before and after 4 weeks on treatment with oral 5-aminosalicylic acid. By means of an intracolonic double-lumen perfusion tube, an isotonic solution was continuously infused 50 cm from the anal verge at a rate of 5 ml/min, and was recovered 30 cm distally by siphonage. Effluents were assayed for tumour necrosis factor by a specific e.l.i.s.a. and for prostaglandin E2 and leukotriene B4 by specific r.i.a.s. 3. The intracolonic release of tumour necrosis factor was undetectable in patients with irritable bowel syndrome, whereas measurable release occurred in 15 out of 19 patients with active ulcerative colitis (P < 0.01). Prostaglandin E2 and leukotriene B4 release were also increased in active ulcerative colitis by comparison with irritable bowel syndrome (P < 0.01). Five out of seven patients with colitis improved with 5-aminosalicylic acid treatment, and tumour necrosis factor release became undetectable or decreased markedly (P < 0.05 compared with before treatment). However, tumour necrosis factor release remained high in the non-responder patients. 4. These findings indicate that intracolonic immunoreactive tumour necrosis factor release is enhanced in active chronic ulcerative colitis, becoming undetectable when mucosal lesions are healed. These results suggest that the luminal release of tumour necrosis factor may serve as an objective index of inflammatory activity in patients with chronic ulcerative colitis.

Adolescent↗

PubMed1994

Abnormal leukotriene C4 released by unaffected jejunal mucosa in patients with inactive Crohn's disease.

The mucosal release of inflammatory mediators is enhanced in active inflammatory bowel disease. This study examines whether leukotriene C4 production occurs in apparently unaffected segments of the gut. The intraluminal release of leukotriene C4 was determined by jejunal perfusion in seven healthy controls, in nine patients with chronic ulcerative colitis, and in 13 patients with Crohn's disease (six with ileal disease, and seven with only colonic). All patients were in clinical remission and none of them had evidence of jejunal involvement. Mild intraluminal irritation with a 2.5 mmol/l deoxycholic acid solution was induced to stimulate local inflammatory mechanisms. The release of DNA (a marker of mucosal desquamation) and prostaglandin E2 (PGE2) was simultaneously measured. Jejunal release of DNA was higher in Crohn's disease patients than in ulcerative colitis or healthy controls. Basal release of PGE2 was similar in the three groups of patients. Basal release of leukotriene C4 was considerably enhanced, however, in Crohn's disease patients compared with healthy controls. In ulcerative colitis patients, basal leukotriene C4 release was non-significantly different from controls. Bile acid perfusion stimulated PGE2, leukotriene C4, and DNA release in all groups studied, but leukotriene C4 release was significantly higher in Crohn's disease patients. It is concluded that in inactive Crohn's disease there is an enhanced intraluminal release of leukotriene C4 in apparently unaffected segments of proximal small bowel, which may reflect fundamental changes in the function of the gut mucosal barrier.

Adult↗

PubMed1994

Role of intestinal microflora in chronic inflammation and ulceration of the rat colon.

Bacteria and their products stimulate inflammatory responses. The effects of different antimicrobial regimens (amoxicillin/clavulanic acid, tobramycin, imipenem, vancomycin, metronidazole) were investigated on the course of experimental colitis induced by trinitrobenzenesulphonic acid (TNB) in the rat. On day 7 and 21 after the induction of colitis, matched groups of control and antibiotic treated rats were subjected to colonic dialysis to measure eicosanoid release, and killed for morphological assessment of the colonic lesions (macro and microscopic scores). Stool samples were cultured. Selective antibiotic treatment against Gram positive, Gram negative or anaerobic bacteria had no effect on colonic lesion scores. By contrast, certain broad spectrum antibiotics (amoxicillin/clavulanic acid or the association of imipenem plus vancomycin) significantly reduced macro and microscopic scores. Rats receiving these antibiotics did not develop chronic colitis as shown by the virtual absence of colonic strictures, adhesions, fibrosis, and granulomas. On day 21 after TNB, the intracolonic release of prostaglandin E2, thromboxane B2, and leukotriene B4 was significantly higher in control than in antibiotic treated rats. Control stool cultures showed abundant colony forming units of both aerobic and anaerobic bacteria. Amoxicillin/clavulanic acid and imipenem plus vancomycin induced appreciable reductions in luminal bacteria. In conclusion, certain broad spectrum antibiotics prevent chronic colitis. The normal colonic flora seems to play an important pathogenetic part in the progression of inflammatory colonic lesions to chronicity.

Animals↗

PubMed1994

[Nitric oxide and Hirschsprung's disease: a causal relation biochemically, immunohistochemically and functionally demonstrated].

UNLABELLED: Hirschsprung's disease may be due to impaired nonadrenergic-noncholinergic inhibitory input in the aganglionic segment of the colon. It has been suggested that nitric oxide (NO) might be the lacking neurotransmitter. Thus, our specific aims were to determine in ganglionic and aganglionic segments: 1. The activity of the NO synthetase (NO-S); 2. The location of this enzyme; and 3. The "in vitro" basal motor activity of the muscle strips and their responses to an NO donor and to an NO antagonist. METHODS: NO synthetase activity was quantified in samples of tissue from both aganglionic and ganglionic segments obtained during surgery in 6 patients with Hirschsprung's disease by the transformation of 14C-L-arginine into 14C-L-citrulline in tissue homogenates. Immunohistochemical staining of the tissues was performed using a polyclonal antibody raised against a peptide sequence of rat brain NO synthetase. Furthermore, in 2 patients we measured "in vitro" the tonic response of muscle strips to an exogenous NO donor (sodium nitroprusside) and to an NO antagonist (L-NAME). RESULTS: NOS activity was undetectable in every aganglionic segment whereas it was present in all ganglionic segments (0.49 +/- 0.09 pmol citrulina/mg.min; mean +/- SE). Immunohistochemically, NO-S was absent in the myenteric plexus of aganglionic segments and it was present in ganglionic segments. "In vitro" basal motor activity of ganglionic segments was normal, with presence of low-frequency contractions (LFC) and summation contraction (SC); in aganglionic segments SC were absent. Sodium nitroprusside induced a marked relaxation (90% from basal) in muscle strips, both aganglionic and ganglionic, precontracted with bethanocol.(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine↗

PubMed1993

The arginine/nitric oxide pathway modulates sphincter of Oddi motor activity in guinea pigs and rabbits.

BACKGROUND: Nitric oxide acts as a neurotransmitter of nonadrenergic, noncholinergic pathways. The present study examined the role of the L-arginine/NO pathway on sphincter of Oddi motility. METHODS: In anesthetized guinea pigs and rabbits, intracholedochal pressure was recorded by a perfused catheter whose open tip was maintained close to the sphincter of Oddi lumen. The contractile responses to cholecystokinin or bethanechol were recorded before and after treatment with either a specific NO synthetase inhibitor (NG-nitro-L-arginine methyl ester) or a donor of NO (sodium nitroprusside). The effect of NO synthase inhibition on isometric tension generated by muscle from rabbit sphincter of Oddi was tested in vitro. RESULTS: Tonic pressure and phasic contractions significantly increased after NO synthase inhibition; responses to cholecystokinin and bethanechol were enhanced. In contrast, sodium nitroprusside reduced the response to cholecystokinin. Isolated muscle from rabbit sphincter of Oddi relaxed in response to the nicotinic agonist dimethyl-4-phenylpiperazinium. Relaxation was eliminated by either the neurotoxin tetrodotoxin or by NG-nitro-L-arginine methyl ester. NO synthase inhibition also suppressed the relaxatory response induced by electrical field stimulation. Calcium-dependent activity of NO synthase was detected in fresh homogenates from guinea pig and rabbit sphincter of Oddi tissue. CONCLUSIONS: NO that is locally generated by a constitutive NO synthase regulates sphincter of Oddi motor function.

Amino Acid Oxidoreductases↗

PubMed1993

Patients with achalasia lack nitric oxide synthase in the gastro-oesophageal junction.

The abnormal function of the lower oesophageal sphincter in achalasia is likely to be due to impaired nonadrenergic, noncholinergic (NANC) inhibitory input. Since recent studies in animals suggest that nitric oxide (NO) is implicated physiologically in the inhibitory responses of the lower oesophageal sphincter, we have investigated whether the synthesis of NO is altered in the gastro-oesophageal junction of patients with achalasia. NO synthase activity was investigated in samples of tissue from the gastro-oesophageal junction obtained during surgery in eight patients with typical achalasia and six non-achalasic controls who underwent oesophagectomy for reasons other than sphincter dysfunction. The NO synthase activity was determined by the transformation of 14C-L-arginine into 14C-L-citrulline in tissue homogenates. In addition, immunohistochemical staining of the tissues was performed using a polyclonal antibody raised against a peptide sequence of rat brain NO synthase. Furthermore, the relaxant response to an exogenous NO donor (sodium nitroprusside, SNP) was measured in vitro in muscle strips obtained from two patients with achalasia and in two non-achalasic controls. NO synthase activity was detected in each of the samples obtained from six control patients (0.59 +/- 0.21 pmol mg-1 min-1; mean +/- SE). By contrast, none of the samples obtained from the eight patients with achalasia had any detectable NO synthase activity. Immunohistochemical studies confirmed the presence of NO synthase in the myenteric plexus of the gastro-oesophageal junction of control patients and its absence in achalasia. SNP relaxed muscle strips precontracted with bethanechol in both control samples and those from patients with achalasia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Influence of dietary fat on duodenal resistance to acid.

Three experimental diets were prepared from a standard formula plus pure oleic, linoleic, or eicosapentaenoic acid (2% by weight). Mucosal resistance to acid was tested in anaesthetised rats fed the experimental diets for at least four weeks (60 rats per diet) by duodenal infusion of HCl (200 to 700 mumol) 30 minutes after pretreatment with either saline or 100 mumol HCl (used as a mild irritant). Rats were killed one hour after the test and the duodenal damage was assessed 'blindly' using a combined macroscopic and histological score. Differences were tested by analysis of covariance of the dose-response curves. Mucosal resistance was similar in the three groups when the acid challenge was given after saline pretreatment. Resistance to acid in all three groups was significantly increased by previous exposure to 100 mumol HCl (p < 0.01). Interestingly, rats fed a linoleic or eicosapentaenoic supplemented diet after pretreatment with HCl developed significantly higher resistance to acid than those fed the diet with oleic acid (p < 0.05). Pretreatment with indomethacin suppressed the difference between diets. In conclusion, dietary polyunsaturated fatty acids enhance duodenal resistance to acid by potentiation of adaptive cytoprotection.

Animals↗