Examination of stomach wall Mg2+-Na+-K+-dependent ATPase, ATP, and ADP in pylorus-ligated rats

Cellular Energetical Actions of "Chemical" and "Surgical" Vagotomy in Gastrointestinal Mucosal Damage and Protection: Similarities, Differences and Significance for Brain-Gut Function

BACKGROUND

The authors, as internists, registered significant difference in the long lasting actions of surgical and chemical (atropine treatment) vagotomy in patients with peptic ulcer during second half of the last century (efficency, gastric acid secretion, gastrointestinal side effects, briefly benefical and harmful actions were examined).

AIMS

1. Since the authors participated in the establishing of human clinical pharmacology in this field, they wanted to know more and more facts of the acute and chronic effects of surgical and chemical (atropine treatment) on the gastrointestinal mucosal biochemisms and their actions altered by bioactive compounds and scavengers regarding the development of gastric mucosal damage and protection.

METHODS

The observations were carried out in animals under various experimental conditions (in intact, pylorus-ligated rats, in different experimental ulcer models, together with application of various mucosal protecting compounds) without and with surgical vagotomy and chemical vagotomy produced by atropine treatment.

RESULTS

1. No changes were obtained in the cellular energy systems (ATP, ADP, AMP, cAMP, "adenylate pool", "energy charge" [(ATP+0.5 ADP)/ (ATP+ADP+AMP)] of stomach (glandular part, forestomach) in pylorus ligated rats after surgical vagotomy in contrast to those produced by only chemical vagotomy; 2. The effects of the gastric mucosal protective compounds [atropine, cimetidine, prostaglandins, scavengers (like vitamin A, β-carotene), capsaicin] disappeared after surgical vagotomy; 3. The extents of different chemical agents induced mucosal damaging effects were enhanced by surgical vagotomy and was not altered by chemical vagotomy; 4. The existence of feedback mechanisms of pharmacological (cellular and intracellular) regulatory mechanisms between the membrane-bound ATPdependent energy systems exists in the gastric mucosa of intact animals, and after chemical vagotomy, but not after surgical vagotomy.

CONCLUSIONS

1. Increased vagal nerve activity takes place in the gastric mucosal damage; 2 both surgical and chemical vagotomy result mucosal protective affect on the gastric mucosal in different damaging experimental models; 3. The capsaicin-induced gastric mucosal damage depends on the applied doses, presence of anatomically intact vagal nerve (but independent from the chemical vagotomy), 4. The central and pheripheral neural regulations differ during gastric mucosal damage and protection induced by drugs, bioactive compounds, scavengers.

Participation of vanilloid/capsaicin receptors, calcitonin-gene-related peptide and substance P in gastric protection of omeprazole and omeprazole-like compounds

The effects of omeprazole and different omeprazole-like compounds, associated with anti-ischaemic, antioxidant and poly(adenosine-diphosphate-ribose) polymerase (PARP) inhibitory properties, on the gastric acid secretion (4 h pylorus-ligated) and indomethacin-induced gastric mucosal damage connected with the specific immunohistochemical distribution of TRPV1, CRGP and SP during the effects of these compounds, were studied. The observations were carried out in CFY-strain rats (180-210 g), according to the standard methods and the above-mentioned parameters were studied in these experimental circumstances without and with application of different compounds. We found that: (1) all of the compounds dose-dependently inhibited the gastric acid secretion and mucosal damage; (2) the expression of TRPV1 receptor, CGRP and SP decreased significantly in both pylorus-ligated and indomethacin-treated animals and (3) the expression of TRPV1 and CGRP was reduced. Meanwhile, no change was obtained in SP expression during the gastric mucosal protection produced by omeprazole and omeprazole-like compounds. The conclusions were that (1) a functional overlap exists between the capsaicin-sensitive afferent and efferent vagal nerve during omeprazole effects; (2) chemical modification of omeprazole molecule offers a new pathway to obtain a new drug for the introduction in the clinical practice.

Role of energy metabolism in drug-induced acute gastric mucosal injuries in humans

BACKGROUND

In various drug-induced gastric mucosal injuries, it has been speculated that changes in gastric mucosal energy metabolism differ according to the cause of injury. This study was conducted to investigate the role of energy metabolism in two drug-induced gastric mucosal injuries in humans.

METHODS

The subjects were patients with acute gastric mucosal injury due to non-steroidal anti-inflammatory drugs (NSAID) or steroids, and normal controls. Two sets of tissue specimens from the antrum and corpus of the stomach were obtained. One specimen from each area was used for histological analysis and the other was stored in liquid nitrogen. The stored tissues were homogenized. Adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) were measured by the luciferin-luciferase method.

RESULTS AND CONCLUSIONS

In the NSAID group, the ATP levels and the total adenine nucleotide (TAN) levels in both the antrum and corpus were significantly lower than in the control group. In the steroid group, no significant differences were observed in either the ATP or TAN levels. The NSAID decreased energy metabolism in the entire stomach while the steroid had a negligible effect on energy metabolism.

Membrane-bound, ATP-dependent energy systems and tissue hypoxia in human gastric mucosa

1. The biochemical measurements of gastric mucosal ATP, ADP, AMP and cAMP offer excellent information on the extent of tissue oxygenation, when the observations are taken simultaneously from the same tissue sample. 2. Adenosine triphosphate is split by membrane-bound enzymes in two directions (to ADP and cAMP), while ADP and cAMP transform to AMP, supplying further energy liberation. 3. The liberated free energy modifies physiologically or pathophysiologically the functions of target organ cells. 4. Different drugs, hormones and mediators, have different effects on the regulation of ATP breakdown (into ADP vs cAMP). 5. The actual tissue level of ATP is a consequence of the equilibrium between the directions of ATP-ADP and ATP-cAMP breakdown, as well as of ATP resynthesis. 6. The biochemical measurement of the reduction in gastric mucosal ATP alone is not enough proof for the existence of tissue hypoxia, because demonstration of the simultaneous elevation of tissue lactate is also necessary.

Age-related change in human gastric mucosal energy metabolism

Many investigators have reported a decrease in mucosal blood flow resulting in impairment of gastric mucosal energy metabolism in animal experiments. Recently, endoscopic studies using reflectance spectrophotometry and laser Doppler flowmetry have indicated that gastric mucosal blood flow in humans decreases with age. However, changes in energy metabolism in human gastric mucosa with age remains obscure. In this study, we measured adenine nucleotides in biopsy samples from human gastric mucosa, using high-performance liquid chromatography, and investigated changes in energy metabolism with age in subjects proven normal endoscopically. Energy charge (EC = (ATP + 1/2 ADP)/ATP + ADP + AMP) in the gastric antral and body mucosa showed decrease with age. When the subjects were divided into two groups, less than and more than 65 years old, the EC level was significantly lower in the latter than the former in both antral and body mucosa (0.65 +/- 0.06 versus 0.74 +/- 0.03 in the antrum, 0.73 +/- 0.04 versus 0.79 +/- 0.04 in the body) and significantly less in the antral mucosa than in body mucosa in both groups. The adenosine triphosphate (ATP) level in the older group showed a significant decrease (6.48 +/- 1.14 versus 9.63 +/- 1.92 in the antrum, 8.59 +/- 1.64 versus 10.60 +/- 2.13 in the body) compared with those less than 65 years old. In the antral mucosa of the older group the adenosine diphosphate (ADP) level was also significantly lower than that in the group less than 65. In conclusion, in the elderly, the energy metabolism in human gastric mucosa is impaired, and this may weaken their defensive mechanism.

Changes in gastric mucosal microcirculation and purine nucleotide metabolism during hemorrhagic shock in rats

Intravital fluorescence microscopy and morphometry were used to study the microcirculation in the rat gastric mucosa during and after hemorrhagic shock. Under control conditions the circulation appeared homogeneous and unaffected by superfusion with 0.1 N HCl. During hemorrhagic shock, scattered areas of the mucosa lost circulation. Morphometry showed that the number of perfused mucosal vessels decreased significantly in the abluminal part of the mucosa both in perfused and ischemic areas, the reduction being most pronounced in the ischemic areas, where the number of perfused luminal vessels also decreased significantly. During reperfusion, bleedings occurred from the mucosa. A key finding was that the bleedings always had their origin at the border zone between ischemic and perfused areas. After hemorrhagic shock adenosine triphosphate and energy charge levels dropped significantly in both perfused and ischemic areas but with significantly lower levels in the ischemic areas. The hypoxanthine levels increased in both perfused and ischemic areas. The experiments show that local mucosal ischemia and accelerated nucleotide degradation are of pathogenetic importance in the development of stress ulcers after hemorrhagic shock. The border zone between circulated and ischemic areas seems to be an area of special interest.

On the genesis of gastric haemorrhage

An hypothesis involving a three step mechanism to account for the initiation of gastric lesions is described. The mechanism necessitates: (a) A drop in the internal energy (ATP) of the mucosal cells of the stomach upon being subjected to stress; either pathological or psychological. (b) Membranes of mucosal "suicidal sacs" containing potent lysosomal acid-hydrolases are rendered fragile and burst, thus releasing hydrolytic acid-hydrolases into the cytoplasm of the mucosal cells as the latter develop an energy deficit under stress. (c) Gastric mucosal cell necrosis, via the degradation of cytoplasmic and mucinous gastric glycoproteins by these lysosomal acid- hydrolases and subjection of the submucosal tissue to the corrosive effects of the luminal fluid containing hydrochloric acid and pepsin, i.e., initiation of gastric haemorrhage. The above mechanism is a general one that describes events associated with the development of gastric lesions regardless of the factor(s) or the agent(s) initiating gastric mucosal haemorrhage.

A biochemical and pharmacological approach to the genesis of ulcer disease. I. A model study of ethanol-induced injury to gastric mucosa in rats

Present concepts of acute ulceration in the gastric mucosa include the hypothesis that mucosal ischemia is an important initiating event. The evidence for this is based upon observations on tissue metabolism and determinations of gastric mucosal blood flow. Using the model of gastric mucosal injury in the rat with ethanol, we have found that mucosal injury could be detected at a time when tissue oxygenation as determined by biochemical, and pharmacological studies of ATP metabolism were not compatible with ischemia. We also found that drugs acting at different subcellular levels were able to both inhibit gastric acid secretion in 4 hour pylorus-ligated rats and gastric mucosal injury after ethanol. Certain drugs, such as histamine and pentagastrin, stimulated acid secretion but inhibited the injury to the mucosa by ethanol indicating that increased cellular activity could occur during the development of mucosal injury.

Interrelationships between membrane-bound ATP-dependent energy systems, gastric mucosal damage produced by NaOH, hypertonic NaCl, HCl, and alcohol, and prostacyclin-induced gastric cytoprotection in rats

Rat gastric mucosal lesions (ulcers) were produced by topical application of 0.2 M NaOH, 25% NaCl, 0.6 M HCl and 96% ethanol. The animals were sacrificed 1 hr after administration of the different necrotizing agents. The number of gastric lesions (ulcers) was noted and their severities scored. Different doses (5 and 50 micrograms.kg-1) of prostacyclin (PGI2) were given intraperitoneally at 30 minutes before administration of necrotizing agents, and their effects were studied on the number and severity of gastric lesions (ulcers). At the time of killing of animals, the rat gastric fundic mucosa was removed for biochemical examinations. Tissue levels of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and lactate were determined enzymatically, while the tissue content of cyclic adenosine monophosphate (cAMP) was measured by radioimmunoassay. The values of the adenylate pool (ATP + ADP + AMP), the ratio of ATP X ADP-1 and the energy charge (ATP + 0.5 ADP X ATP + ADP + AMP-1) were calculated. All biochemical results were calculated in relation to one mg mucosal protein. It was found that:1. the tissue levels of ATP, cAMP, AMP decreased significantly, while the tissue level of ADP increased (without statistical significance) in all models, during the development of gastric mucosal damage; 2. the tissue level of lactate increased only in the model produced by 0.6 M HCl, while its level was unchanged in the other models during the development of gastric mucosal damage; 3. PGI2 decreased dose-dependently the number and severity of gastric lesions (ulcers); 4. the tissue level of ATP, ratio of ATP X ADP-1 and energy charge were decreased significantly, while the tissue level of ADP was increased significantly by PGI2 in all models; 5. the tissue level of lactate and the adenylate pool remained unchanged during the PGI2 effects. It was concluded that: 1. the development of gastric mucosal damage, produced by topical application of 0.2 M NaOH, 25% NaCl, 0.6 M HCl and 96% ethanol, is associated with an active metabolic adaptation of the gastric fundic mucosa; 2. the metabolic adaptation of the rat gastric fundic mucosa is further increased by PGI2, without resulting in hypoxaemic damage of the gastric mucosa; 3. the feed-back mechanism system - between the membrane-bound ATP-dependent energy systems - is broken during the development of gastric mucosal damage produced by different necrotizing agents, which is modified further by PGI2 at the time of gastric cytoprotection.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of glucagon on human gastric mucosa: histochemical studies

We studied the effects of glucagon (2 mg intravenously) on the histochemical localization and staining intensity of 10 enzymes in human gastric mucosa. Glucagon caused a significant increase in the histochemical activity of glucose-6-phosphate dehydrogenase in the undifferentiated neck cells and mucous cells of the foveolae and of ATPase activity in and around the mucosal capillary walls. Glucagon also stimulated mucus secretion from the surface epithelial cells. These changes were observed 15 and 30 min after glucagon in the oxyntic, but no pyloric mucosa. they indicate that glucagon, in addition to its effect on parietal cells, also affects other structures in human gastric mucosa.

Surgical vagotomy and stomach wall ATP and ADP in pylorus--ligated rats

The stomach wall ATP and ADP have been studied in rats, with and without bilateral surgical vagotomy, 24 hr after pylorus ligation. It was observed that the amounts and concentrations of ATP significantly decreased in both parts (corpus + antrum and forestomach) in pylorus-ligated rats, while the amounts and concentrations remained at a significantly higher level in pylorus-ligated + vagotomized rats. Changes in amounts and concentrations of ADP paralleled those of ATP. It has been concluded that a significant decrease of cellular ATP is necessary to produce gastric hypersecretion in ulceration in pylorus-ligated rats. This significant decrease of cellular ATP, in corpus + antrum and forestomach, can be prevented by bilateral surgical vagotomy.

Biochemical gradients in the human gastric and duodenal mucosa in relation to basal acid outputs

The separations and measurements of adenine-adenosine, adenosine monophosphate (AMP), adenosine diphosphate (ADP), adenosine triphosphate (ATP), lipid phosphates (lipid-P), ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) were carried out in the mucosa of the corpus, antrum, and duodenum of patients with decreased, normal, and increased basal acid outputs (BAO). The results were calculated in correspondence to 1.0 mg DNA value. The results indicate: 1) the biochemical composition of the corpus and antral mucosa alters with increase of BAO; 2) a significant difference was found between the biochemical compositions of the mucosa of the corpus and antrum in patients with normal and increased BAO; 3) no significant difference was observed in the biochemical components of duodenal mucosa with different BAO.