Lean body mass, gastric acid, and peptic ulcer

Intra- and interindividual variability in fasted gastric content volume

BACKGROUND

Gastric fluid plays a key role in food digestion and drug dissolution, therefore, the amount of gastric fluid present in a fasted state may influence subsequent digestion and drug delivery. We aimed to describe intra- and interindividual variation in fasted gastric content volume (FGCV) and to determine the association with age, sex, and body size characteristics.

METHODS

Data from 24 MRI studies measuring FGCV in healthy, mostly young individuals after an overnight fast were pooled. The analysis included 366 participants who had up to 6 repeated measurements, with a total of 870 measurements. Linear mixed model analysis was performed to calculate intra- and interindividual variability and to assess the effects of age, sex, weight, height, weight*height as a proxy for body size, and body mass index (BMI).

RESULTS

FGCV ranged from 0 to 156 mL, with a mean (± SD) value of 33 ± 25 mL. The overall coefficient of variation within the study population was 75.6%, interindividual SD was 15 mL, and the intraindividual SD was 19 mL. Age, weight, height, weight*height, and BMI had no effect on FGCV. Women had lower volumes compared to men (MD: -6 mL), when corrected for the aforementioned factors.

CONCLUSION

FGCV is highly variable, with higher intraindividual compared to interindividual variability, indicating that FGCV is subject to day-to-day and within-day variation and is not a stable personal characteristic. This highlights the importance of considering FGCV when studying digestion and drug dissolution. Exact implications remain to be studied.

Normal acid exposure time in esophageal pH monitoring in Asian and Western populations: A systematic review and meta-analysis

BACKGROUND

Esophageal acid exposure time (AET) during 24 h pH monitoring is reproducible and predictive outcomes of treatment for gastroesophageal reflux disease. Several small Asian studies have investigated the normal range of the AET; the range may be different from that in Western populations. We evaluated its normal range in healthy Asian compared to Western subjects.

METHODS

We searched PubMed, Embase, Cochrane Library, and KoreaMed for studies that reported pH monitoring parameters in healthy subjects. Studies that reported the AET values of healthy subjects were eligible for the analyses. The upper limit of normal of the AET was obtained from the 95th percentile of the available raw data or calculated as the mean value +2 standard deviations.

KEY RESULTS

Nineteen Asian and 49 Western studies were assessed. The estimated AET values were analyzed using a bootstrapping technique, weighted according to the sample size. The mean AET was 1.1% and 2.9% in the Asian and Western populations, respectively. The upper limit of the reference range was 3.2% (95% confidence interval [CI], 2.7-3.9%) and 8.2 (95% CI, 6.7-9.9) in the Asian and Western populations, respectively. The normal AET differed between the Asian and Western populations because the CI of the two groups did not overlap.

CONCLUSIONS & INFERENCES

The upper limit of normal of the AET in healthy Asian subjects was 3.2% (95% CI, 2.7-3.9%), which was lower than that of healthy Western subjects.

Prevalence of peptic ulcer in dyspeptic patients and the influence of age, sex, and Helicobacter pylori infection

We investigated the prevalence of peptic ulcer in dyspeptic patients in China to analyze the influence of age, sex, and Helicobacter pylori (H. pylori) infection. The results showed that the prevalence of gastric and duodenal ulcer increased with age. In patients under 60 years old, the prevalence of duodenal and gastric ulcers in females was markedly lower than that in males, especially the prevalence of duodenal ulcer. The prevalence of duodenal ulcer and gastric ulcer in H. pylori-infected patients was markedly higher than in patients without H. pylori infection. In the patients under 60 years old, sex differences were still seen in both H. pylori-positive and H. pylori-negative patients. The prevalence of gastric and duodenal ulcers was markedly increased with age in both H. pylori-positive and H. pylori-negative patients. Multivariate logistic regression analysis showed that age, male sex, and H. pylori infection were three independent risk factors for gastric and duodenal ulcers.

Helicobacter pylori gastritis, the unifying concept for gastric diseases

Helicobacter pylori infection causes a broad spectrum of clinical diseases and the clinical manifestations of the infection depend on host, environmental, and bacterial factors. These factors have an impact on the pattern and severity of gastritis and ultimately determine the clinical outcome of H. pylori infection. Better staging of gastritis may help to identify patients at risk of gastric cancer. In this article we will examine the complex interaction between host, environmental, and bacterial factors in the pathogenesis of H. pylori infection.

Why does Japan have a high incidence of gastric cancer? Comparison of gastritis between UK and Japanese patients

BACKGROUND AND AIMS

The incidence of gastric cancer in Japan is four times higher than in the UK. It usually arises in a stomach with corpus predominant or pangastritis that has undergone extensive atrophy and intestinal metaplasia. We hypothesised that a Japanese population would have a more severe gastritis with a corpus predominant or pangastritis pattern and a greater degree of atrophy and intestinal metaplasia than that found in the UK. To test this we designed a comparative trial.

METHODS

A total of 252 age matched consecutive patients were recruited from the endoscopy services in Leeds and Tokyo. In each centre, 21 patients were prospectively selected from each decennial, between the ages of 20-80 years. All had epigastric discomfort as their predominant symptom. Patients with peptic ulcer, cancer, and oesophagitis were excluded. Five gastric biopsies were examined by two histopathologists using the updated Sydney system. Helicobacter pylori infection was assessed by histology and culture of biopsies and enzyme linked immunosorbent assay and immunoblot of plasma.

RESULTS

Gastritis was found by both pathologists in 59 (47%) UK and 76 (60%) Japanese patients (chi(2) test, p = 0.04). In those patients with gastritis, corpus predominant or pangastritis was commoner in the Japanese (63% Japan v 36% in the UK (chi(2) test, p = 0.003) Atrophy and intestinal metaplasia were more extensive and severe (Mann-Whitney U test, p<0.001) and chronic inflammation and polymorph activity were also greater, especially in the corpus (Mann-Whitney U test, p<0.001). Fifty three of 59 UK gastritis patients (90%) and 67/76 (88%) (chi(2) test, p = 1) Japanese gastritis patients were positive for H pylori. Using a previously described "gastric cancer risk index" among H pylori positive patients, there were significantly more Japanese than UK subjects with a "high risk" score.

CONCLUSION

In Japanese as opposed to English patients, gastritis is more prevalent and severe with more corpus predominant atrophy and intestinal metaplasia. These differences may partially explain the higher incidence of gastric cancer in Japan.

Helicobacter pylori: what do we still need to know?

Helicobacter pylori is a common gastric infection that causes serious complications in a minority of individuals. A great deal is known about the disease, but many unanswered questions remain. Among these, perhaps the most enigmatic is that we do not know how the organism is transmitted. We are uncertain why the prevalence of the disease is falling within the developed population. There is still debate as to its relationship with gastroesophageal reflux disease. It is unclear why there are differences in the international incidence of gastric cancer. Similar uncertainties relate to the reasons why the complications of H. pylori infection have changed over time. In this article, I have hypothesized that a number of these unanswered questions may be related to a putative increase in gastric acid secretion that may have taken place during the past 200 years. To date, there is little confirmatory evidence for this, and it remains a fascinating area that merits more scientific research.

Personal view: to treat or not to treat? Helicobacter pylori and gastro-oesophageal reflux disease - an alternative hypothesis

Helicobacter pylori causes acute on chronic gastritis and is responsible for most peptic ulcers and gastric cancer. However, recent papers have suggested that it may protect against gastro-oesophageal reflux, Barrett's oesophagus and oesophageal cancer. Furthermore, the rapid increase in gastro-oesophageal reflux disease, Barrett's oesophagus and adenocarcinoma of the oesophagus in the developed world has been attributed by some to the falling prevalence of H. pylori. These considerations have led to the suggestion that H. pylori infection should not necessarily be treated, especially in patients with gastro-oesophageal reflux disease. Conversely, data from prospective randomized studies have shown that H. pylori eradication does not cause gastro-oesophageal reflux disease in patients with duodenal ulcer or in the normal population, nor does it worsen the outcome of pre-existing gastro-oesophageal reflux disease. Therefore, although H. pylori is negatively associated with gastro-oesophageal reflux disease, its eradication does not induce the disease. A hypothesis is presented suggesting that the increased prevalence of gastro-oesophageal reflux disease is a result of rising acid secretion in the general population, which, in turn, is a consequence of the increased linear height (a predictor of acid secretion). The greater acid secretion could also explain the decline in the prevalence of H. pylori and perhaps account for the inverse relationship between H. pylori and gastro-oesophageal reflux disease. These considerations are explored in discussing whether H. pylori infection should be treated in infected patients presenting with gastro-oesophageal reflux disease.

Effect of one-month treatment with nonsteroidal antiinflammatory drugs (NSAIDs) on gastric pH of rheumatoid arthritis patients

The use of NSAIDs is strongly associated with peptic ulceration. The inhibition of prostaglandin synthesis with the consequent increase of gastric acidity is considered a possible mechanism. Therefore we decided to assess the effect of one-month treatment with NSAIDs on the circadian gastric pH of rheumatoid arthritis (RA) patients. We studied 11 consecutive patients (one man and 10 women, median age 55, range 26-72 years) with confirmed RA. None was H. pylori positive. A 24-hr gastric pH recording was performed both in basal conditions and after one-month treatment with either indomethacin 150 mg/day (eight cases) or ketoprofen 300 mg/day (three cases). Only the 10 female patients were eligible for final analysis, and six matched healthy subjects not taking NSAIDs were used as control group. The number of 24-hr pH readings for various pH thresholds was calculated for both populations. The highest acid levels (pH < 3.0) did not differ between the two pH profiles of the control group (7440 vs 7391, P = NS), while they predominated after the one-month NSAID treatment (10,339 vs 11,440, P < 0.001) in RA patients. These findings show that there is an increased gastric acidity after one-month of treatment with NSAIDs in female patients with RA of recent onset. This may sustain the rationale of using antisecretory agents to prevent gastroduodenal ulcerations in these patients.

Changes in acid secretion over the years. A 30-year longitudinal study

We studied the effect of aging on gastric acid secretion in 11 physicians who had augmented histamine tests while at medical school in 1962. One of them had a duodenal ulcer at the time. The augmented histamine test was repeated in 1991 and, in addition, upper gastrointestinal endoscopy was done to exclude peptic ulcer and to obtain biopsies for histologic analysis and assessment of Helicobacter pylori status. The mean basal acid output decreased from 7.3 to 1.9 mEq/hr during the 30-year period of follow-up (p < 0.001), and the mean maximum acid output decreased from 29.9 to 20.3 mEq/hr (p < 0.01). The maximum acid output data showed a profound decrease in 4 of the 11 participants, a lesser decrease in 4, and a minimal increase in the remaining 3. Histologic analysis suggested a greater likelihood of atrophic gastritis, H. pylori infection, or both in participants showing a pronounced decrease in acid secretion with aging.

Epidermal growth factor in saliva and gastric juice: response to histamine

Epidermal growth factor (EGF) was measured in saliva and in gastric juice under basal conditions and after histamine stimulation (0.04 mg kg-1h-1). Sixty subjects studied comprised 20 normal volunteers, 20 patients with duodenal ulcer (DU), and 20 patients with non-ulcer dyspepsia (NUD). There was no difference in basal salivary EGF concentrations between control and DU or control and NUD subjects, but the EGF concentration in DU patients exceeded that in NUD patients (p < 0.05). Basal gastric juice concentrations of EGF were similar in all three groups. There was no difference between basal salivary and gastric EGF concentrations (p > > 0.05). After histamine stimulation, salivary and gastric EGF concentrations increased in all three groups: the increase was greater in gastric juice than saliva (p < 0.0001). There were no significant differences in the salivary EGF concentrations of controls and NUD patients, or controls and DU patients, but values were significantly higher when DU and NUD patients were compared (p = < 0.05). In the gastric juice, EGF increased more in DU patients than in controls or NUD patients (p < 0.05). This effect was not linked to the greater acid secretion in DU than in the other groups. There was no influence of gender or smoking on the EGF concentration. This evidence suggests that the stomach itself may be able to secrete large amounts of EGF and that histamine is a potent stimulus. It is more likely that the gastric EGF is responding to the presence of a duodenal ulcer than that lack of EGF is responsible for persistence of the ulcer.

Optimizing acid suppression for treatment of acid-related diseases

Gastric acid is of central importance in the pathogenesis of duodenal ulcer, gastric ulcer, and gastroesophageal reflux disease. Pharmacological reduction of acid secretion is, therefore, the mainstay of current treatment, but the optimal degree of acid suppression remains incompletely understood. This paper considers the ideal ways of assessing and reporting the pharmacological effectiveness of acid-inhibiting drugs and relating such data to clinical efficacy. Twenty-four-hour intragastric pH measurements are widely used for this purpose, although this technique cannot measure secretion quantitatively. Data on suppression of 24-hr intragastric acidity for groups of subjects have been successfully correlated with healing rates for duodenal ulcer, gastric ulcer, and gastroesophageal reflux disease. Three primary determinants of healing have been derived from antisecretory data. These are the degree of suppression of acidity, the duration of suppression of acidity, and the duration of treatment. The order of importance of these determinants varies depending on the disease. Data on 24-hr intragastric acidity should be accompanied whenever possible by data on 24-hr plasma gastrin levels, as the relationship between suppression of acidity and a rise in gastrin varies widely between individuals. It is not possible to predict the plasma gastrin level from the intragastric pH or any other measurement of intragastric acidity. Comparative data sets in groups of subjects may provide useful information. Proton pump inhibitors produce a greater and longer-lasting degree of suppression of acidity than conventional doses of H2-receptor antagonists. For this reason, they are more effective in healing duodenal ulcer and gastric ulcer. However, in view of the importance of duration of treatment, healing rates with the H2-receptor antagonists approach those obtained with proton pump inhibitors if treatment is continued for a longer time. In gastroesophageal reflux disease in particular, although the optimal degree of acid suppression is not yet defined, the consistently superior performance of proton pump inhibitors demonstrates that increased suppression of acidity is clinically beneficial.

Dragstedt, gastric acid and duodenal ulcer

Dragstedt believed that basal hypersecretion of gastric acid was the root cause of duodenal ulcer, that the hypersecretion was due to an increased vagal stimulation, and that vagotomy would therefore cure duodenal ulcer. He introduced vagotomy and demonstrated that the operation was successful in curing most patients of their duodenal ulcers. This article reviews how further research in the succeeding half century has demonstrated that it is the effect of vagotomy on stimulated, rather than upon basal secretion that cures duodenal ulcer and that the apparent basal hypersecretion of patients with duodenal ulcer is due to an increased parietal cell mass. The article points out that there is no convincing explanation as yet of the mechanism whereby vagotomy reduces histamine-stimulated gastric secretion.

Gastric acid secretion and intragastric acidity: measurement in health and disease

Gastric acid secretion tests have limited use in clinical practice. For practical purposes, a pH measurement on a fasting gastric aspirate will provide strong evidence of the presence or absence of achlorhydria. Tests of gastric acidity, in particular 24-h acidity studies, have provided considerable insight into normal and abnormal gastric physiology, and have largely determined the dosing regimens for the management of acid-peptic diseases. Acid tests may be simple to perform, so much so that they have been suggested as 'practicals' for student teaching (Nicol et al, 1991). However, reproducible and meaningful results require careful attention to detail, and the appropriate mathematical analysis is still subject to some debate. It is important that the presentation of the data should allow the reader to assess the response over the 24-h period, and also the range of individual responses. Despite the many years of research into gastric acid secretion, only recently have the effects of age, sex, diet, smoking and mental stress been identified. In addition, many data need to be reviewed in the light of the effects of H. pylori infection on gastrin release. H2-receptor antagonists had been studied extensively before and since their first clinical use in 1974, but surprisingly only recently have the issues of tolerance and rebound been defined. The 24-h intragastric acidity profile remains an essential study before the start of clinical trials on any new drug to be used for the treatment of acid-peptic diseases.

Normal 24-hr ambulatory esophageal pH values. Influence of study center, pH electrode, age, and gender

Although the most sensitive and specific test for diagnosing gastroesophageal reflux disease, normal standards for prolonged esophageal pH monitoring are based on small sample sizes with questions raised about the effects of pH electrode, older age, gender, and methods of data analysis on pH variables. Recently three groups have established normal data bases using similar methodology. Multiple regression and nonparametric analyses showed that the values for the six traditional pH parameters were comparable across study centers. Therefore, the groups were combined for a total study population of 110 healthy subjects (47 men, 63 women, mean age 38 years with a range of 20-84 years). Further nonparametric analyses revealed the following: (1) type of pH electrode (antimony vs glass) is not significantly related to parameters of physiologic acid reflux; (2) age is not independently related to pH parameters; (3) men tend to have more physiologic reflux than women; and (4) older men tend to experience longer episodes of reflux than younger men and women. There was a significant effect of gender and a significant interaction between age and gender on the number of episodes greater than 5 min (P = 0.008). Nearly significant differences were found for percentage of total acid exposure time (P = 0.03), total reflux episodes (P = 0.02), and the longest reflux episode (P = 0.02). We believe these normal esophageal pH values can be used confidently as standards in any laboratory, and consideration should be given to developing separate standards for men and women.

Acid secretion, 1932-92: advances, adaptations, and paradoxes

This paper reviews the evolution of our understanding of various aspects of gastric acid secretion over the past 60 years. Embryologic aspects and neonatal acid secretion are considered, and the relationship between parietal cell mass and acid secretion and the changing concepts of parietal cell activation are discussed. The effect of aging on acid secretion and the relevance of acid secretion in health and disease are reviewed, and current views on adaptation to therapeutic inhibition of acid secretion presented. The aetiologic link between acid secretion and ulcer disease is re-examined, and the role of pepsin, growth factors, and Helicobacter pylori briefly considered.

Lack of necessity for corrections for pyloric losses and duodenogastric reflux in the performance of gastric secretory studies

Gastric secretory studies are subject to considerable error owing to incomplete collections and to contamination by reflux of alkaline duodenal contents. Corrections for these sources of error have been defined, and they have been extensively applied in a research setting. In order to assess their utility in the performance of routine gastric secretory studies, the value of such corrections was assessed in 56 studies in patients with duodenal ulceration (10), previous surgical vagotomy (8), reflux oesophagitis (30) and primary oesophageal motility disorders (8). The effect of such corrections was small, and there were close correlations between uncorrected and corrected acid outputs in all four groups. The status of the vagal efferent gastric fibres was assessed by comparing the acid output after insulin hypoglycaemia with the maximal acid output after pentagastrin (insulin: pentagastrin ratio). The application of the corrections did not alter the conclusion regarding the assessment of vagal status in 55 of the 56 studies performed. It is concluded that such corrections are not necessary in the routine performance of gastric secretory studies.

Comparison of maximal gastric secretion in smokers and non-smokers with and without duodenal ulcer

Maximal gastric secretion was induced in 122 control subjects (without peptic ulcer) and 201 preoperative duodenal ulcer patients by intravenous histamine acid phosphate (130 nmol/kg/h), and measured as Vg (ml/h) and MAO (mmol/h). In both groups, men secreted more than women, and smokers secreted more than non-smokers. Significant correlations were found between maximal gastric secretion on the one hand, and height, age, and chronic smoking on the other. After standardisation for these factors, including standardisation to zero smoking, the subgroups of the controls no longer differed significantly, as was also the case for the duodenal ulcer patients. Thus, differences in height, age, and smoking habit were sufficient to account for the variation in maximal secretion between individuals in either the control or duodenal ulcer groups. Even after standardisation, however, the duodenal ulcer patients still secreted significantly more than the controls, and therefore, although chronic smoking has been shown to affect maximal gastric secretion, it does not appear to be the sole reason for hypersecretion in duodenal ulcer patients.

Increased gastric secretory capacity in smokers without gastrointestinal lesions

The relationship between smoking and gastric secretory capacity was studied in 201 25-40 year old healthy subjects with normal laboratory data and no gastrointestinal lesions. Basal acid output (BAO) and peak acid output (PAO) were determined in all, and basal and stimulated pepsin outputs were measured in 85 participants. The accuracy of the patients' statements was checked by urinary nicotine assay. Basal acid output and PAO were significantly higher in male smokers (n = 55) than in male non-smokers (n = 49). In women PAO in smokers (n = 38) was higher than in non-smokers (n = 59). Female smokers (n = 38) had a higher pepsin output than female non-smokers (n = 23). Eight variables were considered in relation to BAO and PAO: age, height, weight, alcohol abuse, smoking habits, duration of smoking habit, number of cigarettes per day, and the product of years of smoking multiplied by daily number of cigarettes. The daily number of cigarettes X years of smoking was most closely correlated with BAO and PAO by stepwise multiple linear regression analysis. It was concluded that smoking is related to increased gastric acid capacity.

Gastric acid secretion studies in Enugu, using pentagastrin stimulation

Mean acid output was studied in forty-three Nigerian subjects (twenty controls and twenty-three duodenal ulcer patients). 6 micrograms/kg body weight of pentagastrin was given to each after 1 hour basal acid output (B.A.O.) collection. Maximal and peak acid outputs (M.A.O. and P.A.O.) were measured in mmol/hr using the indicator-titration method. Gastric juice volume was measured in mls. For the control the B.A.O., M.A.O. and P.A.O. in mmol/hr were (Mean 1 S.D.) 1.7 +/- 1.6; 13.5 +/- 4.61 and 15.1 +/- 5.3 respectively. The corresponding figures for the duodenal ulcer patients was 3.2 +/- 2.7; 25.1 +/- 8.5; 28.4 +/- 11.1. P less than 0.05, P less than 0.001 and P less than 0.001 respectively). The mean stimulated gastric juice volume of 131.3 +/- 29.6 ml in the controls differed significantly from the volume 198.2 +/- 54.9 in the duodenal ulcer patients (P less than 0.001). 182 mls of gastric juice was found to be the volume above which is duodenal ulcer may be suspected. Acid values are compared with published data and reasons for any differences discussed.

Maximal gastric secretion in smokers and non-smokers with duodenal ulcer

Sex, stature, age and smoking habits were investigated as possible determinants of maximal gastric secretion in pre-operative patients with duodenal ulcer. Stimulation was by an intravenous infusion of histamine (130 nmol kg-1 h-1) in 201 patients. Men were found to secrete significantly more than women, and smokers secreted significantly more than non-smokers. By multiple regression analysis, height and the total number of cigarettes smoked were found to be significant positive, and age significant negative factors in the magnitude of maximal gastric secretion. Upon standardization for these factors, the differences between the sexes and the smoking groups disappeared. It is suggested that, at least in men, chronic smoking increases maximal gastric secretion, and therefore could have a role in the aetiology of duodenal ulcer.

Low acid output in Pima Indians. A possible cause for the rarity of duodenal ulcer in this population

Duodenal ulcer has not been observed in full-heritage Pima Indians, while gastric cancer is relatively frequent. To investigate possible underlying factors for this phenomenon, we determined gastric acid output, gastric emptying rate, and plasma levels of gastrin, pepsinogen I, and pepsinogen II in apparently healthy Pima Indians and in Caucasian controls. The Pimas had significantly lower basal and stimulated outputs of gastric acid and higher fasting and postprandial plasma gastrin concentrations than the Caucasians. Plasma pepsinogen I levels were similar in the two groups, but plasma pepsinogen II was significantly higher and the ratio of pepsinogen I to pepsinogen II was significantly lower in the Pima Indians. In addition, gastric emptying of acaloric liquid meal was significantly delayed in the Pimas. The results suggest that the absence of duodenal ulcer in Pima Indians may be related to low gastric acid production and a slow rate of gastric emptying in this population. The associated findings of hypergastrinemia, hyperpepsinogenemia II, and a low ratio of pepsinogen I to pepsinogen II suggest that the hypochlorhydria may reflect an increased prevalence of chronic gastritis in full-heritage Pima Indians. This, in turn, could represent a risk factor for the development of gastric cancer in this population.

Age behaviour of gastric acid secretion in males and females with a normal antral and body mucosa

In males with a normal gastric mucosa the acid secretion expressed in terms of fat-free body weight (FFB) shows a random distribution with age, whereas in females there is a significant increase. To explain this sex-related discrepancy, we examined maximal pentagastrin-stimulated gastric acid output (AO) and the parietal cell density (P) and thickness (T) in 50 males and 50 females with a normal antral and body mucosa randomly collected from a representative Finnish population sample. Two alternatives were considered: 1) the parietal cell reactivity remains constant, and the age variation in females is due to an increase in the total parietal cell mass, 2) the age variation in females is due to an increase in the reactivity of parietal cells, the total parietal cell mass (P X T X body area (A)) remaining constant. Starting from the first alternative, P and T were measured and showed no correlation with age in males and a decrease in females. The variable A is, according to the formula, expressed by the ratio AO/P X T, and this ratio shows an expected significant correlation with AO in both males and females. However, the variable A showed a significant increase with age in females but not in males. In view of the results of Cox that A should not vary with age, the present results suggest that the ratio AO/P X T in females must include, in addition to body area, other variables, such as the reactivity of parietal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Age- and sex-related behaviour of gastric acid secretion at the population level

Pentagastrin-stimulated gastric acid output and the histology of the antral and body mucosa were examined in 72 computer-selected probands and their 365 relatives, altogether 437 cases. The frequencies of upper abdominal complaints, peptic ulcer and hiatal hernia, and blood group distribution were comparable with those of the population at large. Acid output, expressed as mmol/h, mmol/h/kg of total body weight (TBW), mmol/h/kg of lean body mass (LBM), and mmol/h/kg of fat-free body weight (FFB), correlated with the changes in the body mucosa but not with those in the antrum. Acid output was lower in females than in males when expressed as mmol/h or mmol/h TBW but not when expressed in terms of FFB, which better than LBM accounts for the variation in the gastric surface area and, in this manner, for that of the parietal cell mass. This suggests that the lower acid output in females is due to a smaller gastric surface area and correspondingly smaller parietal cell mass rather than to a lower reactivity of the cells to stimulation. Acid output decreased with increasing age in both sexes, and this was due to a concomitant increase in the incidence and severity of atrophic changes in the body mucosa. An age-related decrease in acid output was not seen in males with a normal body mucosa. In females with a normal body mucosa, however, output expressed in terms of FFB showed a significant increase with age. The reason for this increase is not clear. In males and females with superficial gastritis of the body mucosa acid output decreased with increasing age regardless of the formulation used.

Correlation of salivary and gastric acid secretions in duodenal ulcer patients in tropics

Salivary flow rates on mechanical stimulation by forced spitting method and by chemical stimulation with 10% citric acid and gastric acidity using an augmented histamine test were determined in 20 adult patients suffering from duodenal ulcer and in 20 adult control subjects matched with respect to age, sex, and body weight. Salivary flow rates were found to be much higher in response to chemical than to mechanical stimulus in both the groups. Duodenal ulcer patients exhibited an unexplained exaggerated response to chemical stimulation. Salivary pH, amylase, sodium, and potassium levels showed no significant differences between the two groups. The flow rates by either method generally showed a positive correlation with body weight in both the groups. Histamine stimulated gastric acid secretion was higher in duodenal ulcer patients than in controls. Acid secretion did not appear to be related to weight and also showed no consistent correlation with the salivary flow rates. It was concluded that (1) the salivary flow was dependent on body weight in duodenal ulcer patients as well as in controls, and (2) although salivary gland hyperplasia could be postulated in duodenal ulcer patients on the basis of increased salivary flow, the latter was poorly related to maximal acid secretion and therefore, if a combination of parietal cell and salivary gland hyperplasia did exist, it should be considered as incidental.

Characteristics and tachyphylaxis of gastrin-stimulated gastric acid secretion in the cat

1. The characteristics of gastrin-stimulated gastric acid secretion were investigated in conscious cats fitted with chronic cannulated gastric fistulae, with particular reference to tachyphylaxis. 2. There is a significant postive correlation between the peak acid secretion in response to pentagastrin 8 microgram kg-1 hr-1 and body weight. Male cats secret significantly greater amounts of acid in response to pentagastrin than females. The difference is lessened, but not eliminated, by expressing the acid out put in terms of body weight. 3. Pentagastrin stimulates a dose-dependent increase in acid secretion in the range 0.5-32 microgram kg-1 hr-1 when the response to each dose is assayed on separate occasions. Pentagastrin 64 microgram kg-1 hr-1 does not produce a further increase in acid secretion. The acid response to pentagastrin 1-16 microgram kg-1 hr-1 assayed on a single occasion by a continuous infusion method shows a dose-response relationship up to 8 microgram kg-1 hr-1 when it reaches a plateau of secretion. There is no difference between the two methods of assaying the gastric acid stimulating activity using doses of pentagastrin up to 8 microgram kg-1 hr-1. 4 The acid secretion in response to pentagastrin 8 microgram kg-1 hr-1 reaches a maximum after 45 min of stimulation and thereafter shows tachyphylaxis. Over a period of 5 hr there are at least two phases of tachyphylaxis distinguishable. During the period 0.75--2.5 hr of stimulation there is a fast phase of tachyphylaxis (-32.0 muequivH+kg-1 15 min-1). This is followed by a slow phase of tachyphylaxis (-9.4 muequivH+kg-1 15 min-1) up to 5 hr of stimulation. 5. The absolute rate of the fast phase of tachyphylaxis of acid secretion (muequivH+kg-1 15 min-1) increases with increasing doses of pentagastrin, but rates of tachyphylaxis are similar when expressed as a percentage of the peak acid response to the particular dose of pentagastrin (5.1--7.8% 15 min-1). Synthetic human gastrin-17, the synthetic C-terminal decapeptide of human gastrin and the C-terminal tetrapeptide of gastrin have comparable rates of tachyphylaxis. The possible receptor models for the tachyphylaxis of gastrin-stimulated acid secretion are discussed.

Post-vagotomy insulin test: improved predictability of ulcer recurrence after corrections for height and collection errors

Insulin stimulated gastric secretion was studied in 74 unoperated duodenal ulcer patients (DUs), (20 women and 54 men). Three indices of secretion were studied--observed volume, acid output, and volume of gastric juice corrected for pyloric loss and duodenal reflux (VG). These three measurements were expressed both as peak secretion and as secretion during the 1/2 to two hour period after insulin, and also both before and after standardisation for height, making 12 different indices in all. From the data a significant correlation between insulin-stimulated secretion and height in DUs was found. A method of standardising each patient's secretion for height is described. We confirm a significantly higher insulin-stimulated secretion in men than in women and show that this difference can be explained by their difference in height. For each of the 12 indices of secretion, the range of secretion for the unoperated subjects was obtained. The same indices were measured in 155 postvagotomy patients, including 33 patients with recurrent DUs, and compared with the ranges of secretion established in the unoperated patients. Responses above the lower 95% tolerance limit of the preoperative range were designated positive and those below negative. The Hollander status was determined. It was found that the least satisfactory criterion was Hollander's (7% false negative and 69% false positive). The best was 1/2-2 VG standardised for height (3% false negatives and 43% false positives). The improvement in predictably was significant at the 0-0005 level.

Hypersecretion and length of history in duodenal ulceration

Maximal gastric secretion, measured by the histamine-infusion test, was, as expected, significantly greater in a group of 81 patients with duodenal ulcer than in a group of 72 controls. After standardising for the effect of stature on maximal secretion, only 24 of the patients were found to be true hypersecretors. However, maximal secretion in the ulcer group increased with length of history of symptoms, and extrapolation back to zero length of history suggested that there was no significant hypersecretion at that time. These facts support the hypothesis that it is the presence of the ulcer that leads to hypersecretion rather than the converse. Possible mechanisms involved are chronic ingestion of antacids to counter dyspepsia, or gastric distension due to pylorospasm.

Maximal gastric secretion in patients with chronic airway obstruction

It has been suggested that patients with chronic obstructive chest disease have greater maximal gastric secretion than normal subjects. This problem was studied in 30 subjects using the histamine infusion test with phenol red as a marker to correct for pyloric loss. Clinical, radiological, and physiological criteria were used to define two groups: (1) 13 subjects with normal chests; (2) 14 subjects with unequivocal chronic airway obstruction.

The two groups did not differ significantly in maximal gastric secretion, and this conclusion was not altered by taking stature into account because stature was statistically comparable in the two groups. However, age was significantly different and correction of the secretory data for the diminution of maximal secretion with age improved the correspondence between the groups.

The failure to take stature and age into account may be responsible for conflicting evidence in the past.

The relation between gastric acid secretion and body habitus, blood groups, smoking, and the subsequent development of dyspepsia and duodenal ulcer

One hundred and seventy-six students free of gastrointestinal disease were studied to establish normal acid secretion values for healthy male and female students by the augmented histamine test and to re-examine the relationship between gastric acid secretion and ABO blood groups, body weight, fat-free body mass, height, degree of ectomorphy and mesomorphy, the number of cigarettes smoked per day, and serum cholesterol. A prospective study was then carried out on gastric acid secretion and the subsequent development after 10 years of duodenal ulcers or dyspepsia.Young, healthy medical students have a fairly high mean basal and maximal acid output. There was very little difference in the mean acid outputs of the various ABO blood groups. A significant correlation was shown between acid output and body weight and fat-free body mass, but not with the other measurements of body build. Basal acid output was also related to the number of cigarettes smoked per day. Three students who subsequently developed duodenal ulcers all had a preexistent high level of acid secretion. The acid output was, however, similar in the groups who developed significant or minor dyspepsia or who remained asymptomatic.

Body weight and maximal acid output

Dose-response curves were obtained from forty male control subjects and forty male patients with duodenal ulcer from India on the subcutaneous histamine test.

The body weight and maximal acid output (MAO) showed a positive correlation just significant at the 5% level in control subjects (P=0·05) but not in patients with duodenal ulcer.

The values of MAO on dose-response curves are comparable in control subjects but are appreciably lower in patients with duodenal ulcer from India compared with those from Britain and North America. However, the values expressed as μEq/kg body weight are considerably higher in both groups of subjects from India compared with those from western populations.

The aurate assessment of aximal gastric secretion in control subjects and patients with duodenal ulcer

Maximal gastric secretion was studied in 34 control subjects and 29 patients with duodenal ulcer using the histamine-infusion test with the addition of an inert marker, phenol red, to correct for pyloric losses of gastric secretion.

In the control group, statistically significant correlations were found between maximal gastric secretion and almost all the indices of body stature. Correction for pyloric loss improved all the correlations and raised those correlation coefficients which were not significant to levels of confidence of 95 percent or more.

The validity of calculation of lean body mass from height and weight was checked by the estimation of total body potassium in 26 subjects.

When lean body mass was taken into account it was confirmed that maximal gastric secretion decreased with age, but the sex difference in maximal gastric secretion was no longer statistically significant.

In the duodenal ulcer group, maximal gastric secretion was also significantly correlated with stature, though not with age. It is, therefore, proposed that stature should be taken into account when defining hypersecretion.

As expected, patients with duodenal ulcer produced as a group significantly higher levels of maximal gastric secretion than did control subjects, but the effect appeared to be due to a minority of patients with hypersecretion.

Patients with a history of less than 4 years secreted proportionately less gastric juice than those with a longer history. This finding raises the possibility that gastric hypersecretion is a result of duodenal ulceration rather than a cause.