The role of vasopressin in the pathogenesis of ethanol-induced gastric hemorrhagic erosions in rats. Is vasopressin an endogenous aggressor toward the gastric mucosa?

Neoplastic Pathogenesis Associated with Cigarette Carcinogens

Cigarette smoke is widely regarded as a carcinogenic agent; thus, the incidence of relative neoplasms correlates to cigarette smoking (CS) on a global level. While CS is most commonly associated with carcinomas of the upper and lower respiratory tracts, studies have also associated CS with the pathogenesis of a variety of non-respiratory related neoplasms. The tobacco smoke emitted from cigarettes contains carcinogenic substances that can be harmful to the normal physiology of the human body. This study will elaborate on the incidence and etiology of carcinomas, as well as discuss, in detail, the role of tobacco in the pathogenesis of oral, esophageal, lung, gastric, pancreatic, renal, and bladder carcinomas.

Vasopressin pressor receptor-mediated activation of HPA axis by acute ethanol stress in rats

The plasma arginine vasopressin (AVP), ACTH, and corticosterone levels and the hypothalamic corticotropin-releasing hormone (CRH) content were measured after oral administration of 1 ml of 75% ethanol to rats, a model known to induce acute gastric erosions and stress. Elevated plasma AVP, ACTH, and corticosterone levels were detected 1 h after ethanol administration. Treatment with the vasopressin pressor (V(1)) receptor antagonist [d(CH(2))(5)Tyr(Me)-AVP] before ethanol administration significantly reduced the ACTH and corticosterone level increases. A higher hypothalamic CRH content was measured at 30 or 60 min after ethanol administration. V(1) receptor antagonist injection, 5 min before ethanol administration, inhibited the rise in hypothalamic CRH content. The protein synthesis blocker cycloheximide prevented the hypothalamic CRH content elevation after stress. The AVP-, CRH-, and AVP + CRH-induced in vitro ACTH release in normal anterior pituitary tissue cultures was also prevented by pretreatment with the V(1) receptor antagonist. The results support the hypothesis that stress-induced AVP may not only act directly on the ACTH producing anterior pituitary cells but also indirectly at the hypothalamic level via the synthesis and release of CRH.

Vasopressin deficiency decreases the frequency of gastroduodenal ulceration in humans

Vasopressin is a stress hormone released from the posterior pituitary. In humans suffering from central diabetes insipidus, this release of vasopressin is diminished. It was shown previously that the congenitally vasopressin-deficient Brattleboro homozygous rat is less sensitive to various ulcerogenic stimuli. In this study, we investigated the incidence of gastroduodenal ulceration in vasopressin deficient patients. Data on patients aged 20-70, hospitalized in Hungary between 1992 and 1995 were compared with those on the total population in this age group (6,681,020 in 1994). Subjects with central diabetes insipidus were selected separately (815 cases). Gastroduodenal ulceration was compared in subjects with an intact vasopressin release and vasopressin-deficient patients. The frequencies of gastroduodenal ulceration were also examined separately in male and female subjects. In the total population, the frequency of gastroduodenal ulceration was lower in vasopressin-deficient cases (2.22% versus 0.61%; P < 0.005). Among normal-vasopressin subjects, males have a higher risk of gastroduodenal ulceration than females (3.04% versus 1.46%, respectively; P < 0.001). Among vasopressin-deficient subjects, a similar male:female ratio was observed, but it was not significant (P = 0.36). In comparison to the normal-vasopressin population, the incidence of gastroduodenal ulceration was reduced among vasopressin-deficient males and females by 77% (P < 0.01) and by 82% (P < 0.05), respectively. In conclusion, endogenous vasopressin has a significant harmful action towards the human gastroduodenal mucosa. Peptide and non-peptide vasopressin receptor antagonists might have a potential therapeutic benefit in the treatment (as an adjuvant) and prevention of gastroduodenal ulceration.

Deleterious action of vasopressin in gastroduodenal ulceration: experimental and clinical observations

Vasopressin, released from the posterior pituitary and from the vascular endothelium, can cause vasoconstriction and provoke platelet aggregation, leading to an impaired tissue blood supply. In humans with pituitary diabetes insipidus the central release of vasopressin is diminished, and in the Brattleboro homozygous rat there is congenitally no synthesis of this hormone. The gastroduodenal intramucosal vasopressin level is elevated in normal rats following various acute ulcerogenic challenges (after ethanol, reserpine, indomethacin, cold-restraint stress, endotoxin shock and hemorrhagic shock), and vasopressin-deficient rats are less sensitive to these stimuli. In a hospital- and population-based case-control, age-matched retrospective study, the incidence of human gastroduodenal ulceration is significantly higher in the normal population (in whom the release of vasopressin is presumed to be intact) than in the vasopressin-deficient one (central diabetes insipidus patients). In conclusion, endogenous vasopressin plays an aggressive role in development of gastroduodenal ulceration, especially that related to stress.

Seasonal changes in symptomatic duodenal ulcer activity in Taiwan: a comparison between subjects with and without haemorrhage

OBJECTIVES

To examine if climatic changes may influence the presentation of pain and haemorrhage in patients with duodenal ulcers.

DESIGN

Cross-sectional study.

SETTING

Tertiary referral centre.

SUBJECTS

A total of 10,331 symptomatic duodenal ulcer diseases were diagnosed from 1989 to 1996. The patients who had any extrinsic factors that might influence the exacerbation of duodenal ulcer were not included. Patients were divided into those whose ulcer bled once or repeatedly as distinct from those whose ulcers caused pain without haemorrhagic complications. Patients with acute cholangitis diagnosed in the same period were studied as controls.

RESULTS

During the 7-year period, 10,331 symptomatic duodenal ulcer diseases were diagnosed. Amongst these, 5328 showed active duodenal ulcer without haemorrhage, 2088 showed acute duodenal ulcer with stigmata of recent haemorrhage, and 2915 showed a deformed bulb. The incidence of total duodenal ulcers showed significant monthly variation and was found to be more common from November to March (P < 0.001). The monthly incidence of total episodes of upper gastrointestinal tract bleeding peaked from November to March (P < 0.001) with significant variation. The monthly incidence of bleeding episodes from duodenal ulcer only was the same (P < 0.001). In patients whose duodenal ulcers repeatedly caused pain without haemorrhage, there were significant monthly fluctuations, with peak months from December to March (P < 0.001). In the control diagnosis, there were no significant calendar variations (P = 0.85).

CONCLUSIONS

Our study has shown that both groups of patients demonstrated similar monthly fluctuations. The incidence is significantly higher during the cold seasons. These data suggest that climatic changes may influence the presentation of pain and haemorrhage in duodenal ulcer patients.

Endogenous vasopressin increases acute endotoxin shock-provoked gastrointestinal mucosal injury in the rat

Administration of a low dose of endotoxin (from Escherichia coli, 3 mg kg(-1), i.v.), which does not affect vascular permeability or blood pressure over 1 h, leads to the release of endogenous vasopressin and damage to the mucosal microvasculature. Thus, endogenous vasopressin could be involved in septic shock. In the present study, we investigated the role of endogenous vasopressin in gastrointestinal mucosal injury induced by acute endotoxin shock, which was generated in rats by administering a high dose of E. coli endotoxin (50 mg kg(-1), i.v.). Tissues were removed 15 min after endotoxin. The vasopressin V1 receptor antagonist, d[CH2]5Tyr[Me]arginine-vasopressin (0.2-1 microg kg(-1), i.v.), was injected 10 min before endotoxin. Monastral blue (30 mg kg(-1), i.v.), which stains damaged vasculature, was injected 10 min before autopsy. Endotoxin reduced systemic arterial blood pressure (from 115+/-5 to 42+/-4 mmHg), generated macroscopic and microvascular injury, and elevated plasma vasopressin levels (from 3.4+/-0.2 to 178+/-16 pg ml(-1)). The vasopressin V1 receptor antagonist reduced this macroscopic injury, and in the vasopressin-deficient Brattleboro rat a similar reduction of gastrointestinal mucosal damage was found. Substantial decreases in endotoxin-induced microvascular damage were observed in each tissue, e.g., the gastric Monastral blue staining was reduced by 47+/-3% and 96+/-3% (P < 0.01) after vasopressin V1 receptor antagonist treatment and in Brattleboro rats, respectively. Vasopressin, acting through its V1 receptors, thus appears to be involved in acute endotoxin shock-provoked gastrointestinal injury.

Is smoking still important in the pathogenesis of peptic ulcer disease?

The pathogenesis of peptic ulcer disease is multifactorial, including the effects of Helicobacter pylori, gastric acid, pepsin, gastroduodenal motility, smoking and nicotine, and the complex interaction of an array of other so-called aggressive and protective factors. Since the discovery and acceptance of H. pylori as a major etiologic agent in peptic ulcer disease, the role of smoking has received less attention. Smokers are more likely to develop ulcers, ulcers in smokers are more difficult to heal, and ulcer relapse is more likely in smokers. These clinical observations may be explained by the adverse effects that smoking has on mucosal aggressive and protective factors. Of the aggressive factors, smoking appears to have no consistent effect on acid secretion. However, smoking impairs the therapeutic effects of histamine-2 antagonists, may stimulate pepsin secretion, promotes reflux of duodenal contents into the stomach, increases the risk for and harmful effects of H. pylori, and increases production of free radicals, vasopressin, secretion by the pituitary, secretion of endothelin by the gastric mucosa, and production of platelet activating factor. Smoking also affects the mucosal protective mechanisms. It decreases gastric mucosal blood flow and inhibits gastric mucous secretion, gastric prostaglandin generation, salivary epidermal growth factor secretion, duodenal mucosal bicarbonate secretion, and pancreatic bicarbonate secretion. These adverse effects of smoking on aggressive and protective factors quality it as an important contributor to the pathogenesis of peptic ulcer disease and indicate that smoking plays a significant facilitative role in the development and maintenance of peptic ulcer disease.

Effects of smoking and nicotine on the gastric mucosa: a review of clinical and experimental evidence

Epidemiological and experimental evidence have shown that nicotine has harmful effects on the gastric mucosa. The mechanisms by which cigarette smoking or nicotine adversely affect the gastric mucosa have not been fully elucidated. In this report, clinical and experimental data are reviewed. The effects of nicotine from smoking on gastric aggressive or defensive factors are discussed. Nicotine potentiates gastric aggressive factors and attenuates defensive factors; it also increases acid and pepsin secretions, gastric motility, duodenogastric reflux of bile salts, the risk of Helicobacter pylori infection, levels of free radicals, and platelet-activating factor, endothelin generation, and vasopressin secretion. Additionally, nicotine impairs the therapeutic effect of H2-receptor antagonists and decreases prostaglandin synthesis, gastric mucosal blood flow, mucus secretion, and epidermal growth factor secretion. Although many of the studies provide conflicting results, the bulk of the evidence supports the hypothesis that nicotine is harmful to the gastric mucosa.

Aggressive role of vasopressin in development of different gastric lesions in rats

The effects of endogenous or exogenous vasopressin in models of gastric mucosal injury with a different pathophysiology (ethanol, indomethacin, reserpine, cold-restraint stress and haemorrhagic shock-induced lesions) were investigated in rats. [Mca1,TyrMe2,Arg8]vasopressin, a vasopressin pressor (V1) receptor antagonist, was found to reduce dose dependently the extent of the lesions in all models, and to protect the deeper layer of the mucosa (assessed by histology). Endogenous vasopressin deficiency, as in Brattleboro homozygous rats, had a similar effect. [Lys8]Vasopressin injected exogenously aggravated all types of lesions in normal rats. Circulating vasopressin levels were increased by ethanol, reserpine, cold-restraint stress and haemorrhagic shock, but not by indomethacin, whereas the intramucosal vasopressin content was found to be elevated in all models. Additionally, specific binding sites for vasopressin were shown on the blood vessels of the gastric mucosa (assessed by autoradiography). It is concluded that vasopressin plays a significant aggressive role in the generation of these types of lesions.

A study on the vasopressin induced delay in the gastrointestinal transit in mice: possible mechanism of action

The effect of arginine vasopressin (AVP) on the gastrointestinal (GI) transit and its possible mechanism were studied using charcoal meal test in mice. A dose related inhibitory effect was recorded. The effect appears to be independent of the time allowed between AVP administration and testing. The studies on the mechanism reveal that AVP acts without involving V1 and V2 vasopressin receptors. An almost complete reversal of the effect by physostigmine and potentiation by atropine indicate that AVP might act through an inhibition of the release of acetylcholine. However, the neural nicotinic receptors mechanisms do not seem to contribute since hexamethonium failed to modify the AVP action. Further, a partial antagonism by naloxone or prazosin pretreatment indicates that opioid and alpha 1 adrenergic systems also contribute to this action of AVP. However, the effect appears to be independent of alpha 2 and beta adrenergic systems since yohimbine and propranolol failed to modify the same.