Role of vagal and splanchnic capsaicin-sensitive afferents in enterogastric inhibition of acid secretion in rats

The role of capsaicin-sensitive afferent innervation and neural pathways involved in the enterogastric inhibition of gastric acid secretion by luminal acid was investigated in urethan-anesthetized rats. Intestinal perfusion with graded concentrations of HCl (50, 75, and 100 mM) for 1 h dose dependently inhibited both thyrotropin-releasing hormone (TRH) analogue- and pentagastrin-stimulated acid output (P < 0.01). The inhibitory effect of intestinal perfusion with HCl (100 mM) on pentagastrin-stimulated acid secretion was blocked by bilateral vagotomy, whereas celiac ganglionectomy had no effect. Systemic capsaicin pretreatment (125 mg/kg sc) reduced the antisecretory effects of luminal acid on both TRH analogue- and pentagastrin-stimulated acid secretion. Neither selective perivagal nor selective periceliac capsaicin treatments (1% solution) modified the antisecretory effect of intestinal perfusion with HCl (75 mM) on TRH analogue-stimulated acid secretion. However, combined selective perivagal plus periceliac capsaicin treatment reduced it to the same extent as systemic capsaicin treatment. We conclude that enterogastric inhibition of acid secretion by luminal acid in urethan-anesthetized rats is mediated by extrinsic reflexes involving both vagal and splanchnic capsaicin-sensitive afferent fibers.

Interleukin-1 receptor antagonist does not prevent endotoxin-induced inhibition of gastric acid secretion in rats

The underlying mechanisms involved in endotoxin-induced inhibition of gastric acid secretion were investigated in conscious rats with pylorus ligation for 2 hr. Intraperitoneal injection of endotoxin (0.1, 1, and 5 micrograms/rat) inhibited gastric acid output by 31%, 80%, and 84% respectively. Intraperitoneal endotoxin (1 microgram/rat) -induced inhibition of gastric acid secretion was not altered by pretreatment with the interleukin-1 receptor antagonist, IL-1RA, indomethacin, naloxone, or capsaicin. Treatments were injected peripherally at doses previously shown to antagonize the antisecretory effect of exogenous interleukin-1 beta, to inhibit prostaglandin synthesis in the stomach and brain, to block opiate receptors, and to alter functioning of unmyelinated afferent nerve fibers. These results indicate that the antisecretory effect of endotoxin can be expressed by factors other than interleukin-1, prostaglandins, or opioid peptides that do not require the integrity of capsaicin-sensitive afferent pathways.

Central interleukin-1 beta-induced inhibition of acid secretion in rats: specificity of action

It is well established that IL-1 beta acts in the brain to potently inhibit gastric acid secretion in pylorus-ligated rats. The present study was designed to further investigate the specificity and mechanisms of the centrally mediated antisecretory action of IL-1 beta in conscious rats. Intracerebroventricular injection of IL-1 beta (100 ng) decreased acid secretion in pylorus-ligated rats and inhibited basal and pentagastrin-stimulated acid secretion in rats with chronic gastric fistula. The antisecretory effect of IL-1 beta (100 ng) injected into the lateral ventricle of pylorus ligated rats was completely reversed by prior intracerebroventricular injection of the IL-1 receptor antagonist, IL-1ra, (100 micrograms). Peripheral administration of the somatostatin monoclonal antibody, CURE.S6, did not modify intracisternal IL-1 beta-induced inhibition of acid secretion in pylorus ligated rats. IL-6 and tumor necrosis factor-alpha (100 ng) injected intracisternally did not influence gastric acid secretion in pylorus-ligated rats. These data show that IL-1 beta action in the CNS is mediated through interaction with specific IL-1 receptors and is selective to this cytokine. IL-1 beta antisecretory action can be observed under basal and pentagastrin-stimulated conditions and is independent from somatostatin release in the periphery.

Potent inhibition of gastric acid secretion and ulcer formation by centrally and peripherally administered interleukin-1

IL-1 beta is one of the most potent centrally acting inhibitors of gastric acid secretion in rats. Sites of action have been located in the anterior/preoptic area and paraventricular nucleus of the hypothalamus where other biological activities of IL-1 have also been described. IL-1 beta action is, so far, quite unique to this cytokine and its action is not reproduced by IL-2 or TNF alpha. The IL-1 effect involves prostaglandin pathways and is unrelated to CRF. Similarly, systemic injection of IL-1 induces a long lasting inhibition of acid secretion through prostaglandin-dependent mechanisms. Several findings support the possibility that the effect of systemic IL-1 can be CNS-mediated and/or exerted at the periphery through local release of PG in the stomach. Exogenous IL-1 given into either the circulation or the cerebrospinal fluid also inhibits gastric injury induced by a variety of experimental models (stress, aspirin, ethanol). Such a protective effect is mediated through the inhibition of acid secretion and prostaglandin release, although other mechanisms may also contribute. Whether endogenously released IL-1 beta exerts a protective role in the gastric mucosa is still to be investigated.

Interleukin-1 beta acts at hypothalamic sites to inhibit gastric acid secretion in rats

It has been established that interleukin-1 beta (IL-1 beta) injected into the cerebrospinal fluid inhibits gastric acid secretion in rats. Brain sites of action of IL-1 beta were investigated in conscious rats implanted unilaterally with chronic hypothalamic cannula. Gastric acid secretion was monitored 2 h after pylorus ligation. Human recombinant IL-1 beta (10 ng) microinjected into the medial preoptic area, anterior hypothalamus, and paraventricular nucleus inhibited gastric acid secretion by 76-83%. IL-1 beta microinjected into the ventromedial hypothalamus and other hypothalamic sites outside of responsive sites had no effect. IL-1 beta inhibitory action in the medial preoptic area was dose related (0.1-10 ng), prevented by indomethacin (5 mg/kg ip), and mimicked by prostaglandin E2. These results show that IL-1 beta acts in the medial preoptic area/anterior hypothalamus and paraventricular nucleus to inhibit acid secretion in pylorus-ligated rats and that IL-1 beta action is likely to involve prostaglandin E2.

Potent inhibition of gastric acid secretion by intravenous interleukin-1 beta and -1 alpha in rats

The influence of human and rat recombinant interleukin-1 (hIL-1 beta and -1 alpha and rIL-1 beta) on acid secretion was investigated in conscious pylorus-ligated rats. Intravenous injection of either hIL-1 beta, hIL-1 alpha or rIL-1 beta dose dependently inhibited gastric acid output with an ED50 of 0.05 microgram, 0.5 microgram and 2.2 micrograms, respectively. The antisecretory action of IL-1 beta was associated with an increase in circulating levels of gastrin. hIL-1 beta-induced inhibition of acid secretion was dose dependently reversed by peripheral injection of the IL-1 receptor antagonist, IL-RA, with a dose ratio of 1:10(3) for complete reversal. The inhibitory effect of hIL-1 beta was blocked by indomethacin and was not modified by IV injections of the CRF receptor antagonist, alpha-helical CRF(9-41), or the monoclonal somatostatin antibody CURE.S6, or by systemic capsaicin pretreatment. These results show that systemic hIL-1 beta-induced inhibition of gastric acid secretion is mediated through IL-1 receptors and prostaglandin pathways, and does not involves CRF receptors, afferent fibers, or changes in circulating gastrin or somatostatin levels.

Role of central prostaglandin E2 in the regulation of gastric acid secretion in the rat

The central action of prostaglandin E2 (PGE2) on gastric acid secretion was investigated in rats by comparing the effects of intracisternal (i.ci.) and i.v. administration of PGE2 and the influence of i.ci. injection of indomethacin on acid secretion and PGE2 generation in the brain and stomach. I.ci. injections of PGE2 (1-10 micrograms) or the stable analog, 16,16-dimethyl PGE2, (0.01-0.1 micrograms) induced a dose dependent inhibition of baclofen-stimulated gastric acid secretion by 0-82% and by 7-87% respectively. I.v. infusion of PGE2 also induced a dose related inhibition of baclofen-stimulated acid secretion, but 10 fold higher doses were required. I.ci. or i.v. injection of indomethacin in doses ranging from 50 to 500 micrograms/rat, produced a similar dose dependent inhibition of the PGE2 generation in both the gastric mucosa and brain cortex measured 1 h post injection. I.ci. injection of indomethacin (500 micrograms) increased within 10 min acid secretion with a peak response at 20-30 min; 60-120 min post injection, when prostaglandin synthesis was inhibited by 90%, basal and baclofen-stimulated acid output were not altered. These results further establish that PGE2 acts in the brain to inhibit vagally stimulated gastric acid secretion in rats, and do not support a tonic inhibitory influence of endogenous brain PGE2 in the regulation of gastric acid secretion. In addition, these data showed that indomethacin injected i.ci. at 500 micrograms does not induce a selective inhibition of prostaglandin synthesis in the brain.

Gastric cytoprotection by intracisternal interleukin-1 beta in the rat

The effects of intracisternal (ic) injection of recombinant interleukin-1 beta (IL-1) on absolute ethanol-induced gastric necrotic lesions were studied in conscious rats. IL-1 given ic inhibited ethanol-induced gastric lesions. The cytoprotective effect was dose dependent (ED175 ng/rat), long lasting with a maximal action when given 1-3 h prior to ethanol, blocked by ic injection of a IL-1 receptor antagonist protein (IRAP), and by intraperitoneal injection of indomethacin. IL-1, injected ic, was detected in the peripheral blood. However, IL-1 serum levels were lower after IL-1 injection ic than after ip at a dose giving equal gastric protection. These data show that ic IL-1 induces long lasting gastric protection mediated by interaction with IL-1 receptors and prostaglandin pathways at central and/or peripheral sites that remain to be localized.

Increased gastric PGE2 biosynthesis in cirrhotic patients with gastric vascular ectasia

Plasma levels of glucagon, secretin, norepinephrine, arginine-vasopressin, and prostaglandin biosynthesis in the gastric mucosa were determined in cirrhotic patients with gastric vascular ectasia associated with hypoacidity, in cirrhotics without this lesion, and in healthy controls. Plasma concentrations of glucagon, secretin, and norepinephrine were similar in cirrhotics with gastric vascular ectasia and cirrhotics without this lesion, these concentrations being significantly higher (p less than 0.05) than in healthy controls. However, there was no significant difference between plasma levels of arginine-vasopressin in patients with cirrhosis (with or without gastric vascular ectasia) and those in healthy controls. The biosynthesis of prostaglandin E2 in the antrum of the gastric mucosa was significantly higher in cirrhotics with gastric vascular ectasia than in cirrhotics without this lesion (p less than 0.05) and healthy controls (p less than 0.005). Prostaglandin E2 in the corpus was significantly higher (p less than 0.05) in cirrhotics with gastric vascular ectasia than in healthy controls. The biosynthesis of 6-keto PGF1 alpha (a stable metabolite of prostacyclin) and PGF2 alpha in the corpus and antrum of gastric mucosa was not significantly different in cirrhotics with gastric vascular ectasia, cirrhotics without this lesion and healthy controls. Since prostaglandin E2 has a vasodilator and acid-inhibitory effect, we speculate that high content of this prostanoid in the gastric mucosa may play a role in the pathogenesis of ectatic capillaries and acid inhibition present in some cirrhotic patients.

Gastric vascular ectasias in cirrhosis: association with hypoacidity not related to gastric atrophy

To investigate whether hypergastrinemia and low serum levels of pepsinogen I are associated with gastric hypoacidity in cirrhosis with capillary ectasia of gastric mucosa and whether this alteration is secondary to the presence of atrophic gastritis, two groups of patients were studied: 1) 12 cirrhotic patients with diffuse gastric red spots at the endoscopic examination, and 2) 12 cirrhotic patients with endoscopically normal mucosa. Vascular ectasia of the gastric mucosa was histologically confirmed in all patients with gastric red spots. The study of base-line and stimulated acid gastric secretion showed that 9 of 12 (75%) cirrhotics with gastric vascular ectasia had achlorhydria and that 8 of these 9 patients had high base-line gastrin serum levels (greater than 130 pg/ml) and low base-line pepsinogen I serum levels (less than 20 ng/ml). Base-line gastrin and pepsinogen I serum levels were significantly greater and lower, respectively, in patients with gastric vascular ectasias than in cirrhotics without these lesions. None of the patients of either group had complete atrophy in the corpus of the stomach, and only 4 of the 9 cirrhotics with gastric vascular ectasia and achlorhydria had moderate atrophy. These results show that achlorhydria is frequently associated with hypergastrinemia and low pepsinogen I serum levels in patients with cirrhosis and gastric vascular ectasias and suggest that this disturbance is not secondary to a morphologic abnormality of the gastric mucosa.

Comparison of snare and large forceps biopsies in the histologic diagnosis of gastric vascular ectasia in cirrhosis

To compare snare and large forceps biopsies in the histologic diagnosis of gastric vascular ectasia (GVE) in cirrhosis, two groups of patients were studied: (a) 8 cirrhotic patients in whom endoscopy disclosed multiple gastric red spots (GRS), and (b) 5 cirrhotic patients with no GRS. Histologic examination of snare specimens identified dilated capillaries in the mucosa of the stomach in 75% of the cirrhotic patients with GRS, while large forceps specimens enabled the diagnosis of GVE only in 20% of the cases (p less than 0.05). Morphometric analysis of snare specimens demonstrated a significantly greater mean mucosal capillary cross-sectional area in cirrhotic patients with GRS than in cirrhotic patients without these lesions (p less than 0.05), while no differences in this parameter was observed in large forceps specimens. These findings indicate that gastric mucosal specimens obtained with large forceps are not useful for establishing the histologic diagnosis of GVE in cirrhotic patients with GRS.

Somatostatin compared with cimetidine in the treatment of bleeding peptic ulcer without visible vessel

In a randomized double-blind trial 100 patients with severe bleeding peptic ulcers were treated with an intravenous (i.v.) infusion of cimetidine or somatostatin. Only those patients in whom endoscopy performed within 6 h of admission showed non-arterial bleeding or signs of recent haemorrhage without a visible vessel entered the trial. The two treatment groups were well matched for age, sex, presence of underlying disease, prior ingestion of ulcerogenic drugs, tobacco habits, type of bleeding, haematocrit at admission, presence of hypovolaemic shock, source of bleeding and endoscopic findings. Four patients in each group were excluded after randomization. Further haemorrhage occurred in eight (17.3%) patients in the somatostatin group and in 10 (21.7%) in the cimetidine group, but the difference was not statistically significant. The number of surgical procedures, blood transfusion requirement, duration of hospitalization and mortality rates were similar in the two treatment groups. These results suggest that somatostatin does not improve the results obtained with cimetidine in patients with bleeding peptic ulcer, in whom the endoscopy discloses non-arterial bleeding or signs of recent haemorrhage without a visible vessel.

Conservative management of bleeding duodenal ulcer without a visible vessel: prospective randomized trial

Between January 1983 and December 1985, 305 patients were admitted to our hospital because of bleeding duodenal ulcer. A subgroup of 69 patients aged 50 or above in whom emergency endoscopy showed non-arterial bleeding or signs of recent haemorrhage without a visible vessel entered a prospective therapeutic trial. The patients were randomized to receive either (1) early surgery, implying immediate operation, or (2) expectant management, with surgery reserved only for patients with further haemorrhage. The two groups were homogeneous with respect to age, sex, prior ingestion of ulcerogenic drugs, mode of bleeding, admission haematocrit, number with hypovolaemic shock and number with active bleeding on initial endoscopy. Overall mortality was 8.6 per cent. Mortality in patients submitted to early surgery was five times higher than that in those allocated to expectant therapy (14.7 per cent versus 2.9 per cent; risk ratio 5.07). The results suggest that expectant management is advisable in patients with bleeding duodenal ulcer not bleeding massively and in whom endoscopy does not disclose spurting arterial bleeding or a visible vessel.