Acid Perfusion Research Articles

OESOPHAGEAL FUNCTION IN CHILDHOOD ASTHMA

Aim: This study aimed at revealing the prevalence of oesophageal dysfunction (OD) in childhood asthma and healthy controls, its relation to different types of asthma, to medication and to symptoms of OD. Methods: Fifty-five subjects, 8 to 19 years of age, with moderate or severe bronchial asthma, and 28 healthy controls, 11 to 16 years of age, were interviewed about symptoms and investigated with oesophageal manometry combined with pH reflux tests, acid perfusion test (APT) and acid clearing test. Results: OD was found in 33 of 55 subjects (60%) with asthma and in 4 of 28 healthy controls (14%, p<0.01). Ten of 18 subjects (56%) with nocturnal or morning asthma at least 100 days last year had a positive APT as compared to 16% in those with less severe asthma (p<0.01). OD was as frequent in allergic as in non-allergic asthma. Theophylline or beta2-stimulants were not more often used by asthmatics with OD than by those with normal oesophageal function. In the asthmatic subjects OD-symptoms (acid regurgitation, heartburn, dysphagia) were significantly related to OD (p<0.001). Conclusion: OD was common in moderate and severe childhood asthma and all patients with OD-symptoms had OD. A positive APT was common in youngsters with frequent nocturnal or morning asthma. This finding supports our hypothesis that nocturnal asthma may be reflexly provoked, by gastro-oesophageal reflux, in patients with an acid hypersensitive oesophagus.

Inhibition of neurotensin release by a cyclic hexapeptide analog of somatostatin

Studies were performed to determine whether the cyclic hexapeptide analog of somatostatin, cyclo(N-Me-Ala-Tyr-D-Trp-Lys-Val-Phe) II, could alter circulating levels of neurotensin (NT) and inhibit the release of NT from small intestine following the intraluminal perfusion of lipid and ETOH. The small intestine of anesthetized rats was perfused with 0.9% NaCl, 1 mM ETOH, 100 mM ETOH or 1 mM oleic acid with and without the intravenous infusion of the somatostatin analog. Plasma samples collected from the superior mesenteric vein were extracted, chromatographed on HPLC and assayed with both C-terminal and N-terminal antisera to NT. The basal circulating levels of chromatographically and immunochemically identified NT observed during the perfusion of the small intestine with 0.9% NaCl were significantly lower ( p<0.01) during the IV infusion of the somatostatin analog as compared to animals infused IV with saline. The 2–3 fold increase in plasma levels of NT observed with the intestinal perfusion of oleic acid and ETOH did not occur in animals simultaneously infused IV with the somatostatin analog. The somatostatin analog was also effective in decreasing the basal levels of NT metabolite NT (1–8) as well as inhibiting the increase in this metabolite that accompanies the stimulated release of NT.

Pathogenesis of Steatorrhea in Primary Biliary Cirrhosis

To investigate the pathophysiology of steatorrhea in primary biliary cirrhosis, the severity of steatorrhea, small bowel histology and function, cholestasis, exocrine pancreatic secretion and liver histology were studied. Twenty-four primary biliary cirrhotic patients had a quantitative stool fat collection, serum bilirubin and alkaline phosphatase and liver biopsies. From this group, ten had further studies: a small bowel biopsy (n = 7); a D-xylose test (n = 9); measurement of pancreatiobiliary concentrations and outputs after intravenous cholecystokinin (n = 10); essential amino acid perfusion of the duodenum (n = 9), and eating a test meal (n = 7). D-xylose absorption was normal, and only one patient had a minimal small bowel mucosal abnormality. Pancreatic lipase outputs in response to cholecystokinin were low in two primary biliary cirrhotic patients, but were greater than 10% of normal. Postprandial lipase outputs were normal except in one patient who had abnormal duodenal acidification. Mean enzyme outputs in primary biliary cirrhotic patients were normal in response to essential amino acid perfusion; but 6 had low lipase and 5 had low trypsin outputs which were associated with decreased bile acid outputs (p less than 0.03). Severity of steatorrhea was associated with reduced bile acid outputs and concentrations (r = 0.82; p less than 0.0001), degree of cholestasis (serum bilirubin; r = 0.88; p less than 0.001) and advanced histologic stages (p less than 0.005). Severe intraluminal bile acid deficiency combined with a submaximal intraluminal stimulus (essential amino acids) may be associated with decreased exocrine pancreatic secretion in primary biliary cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Esophageal motor function and response to acid perfusion in patients with symptomatic reflux esophagitis

There is much evidence to suggest that peristaltic function is defective in esophagitis patients and that this defect may contribute to prolonged acid exposure, promoting esophageal mucosal injury. Abnormal peristalsis may also be related to the generation of reflux symptoms. We evaluated primary peristalsis and its relationship to symptoms under basal conditions and during saline and HCl perfusion in 15 symptomatic reflux patients with gross esophagitis and 15 healthy controls. In the basal state, LES pressure (15.3 vs 25.1 mm Hg) and peristaltic amplitude (74.2 vs 104.8 mm Hg) were significantly lower in subjects with gastroesophageal reflux disease (GERD) (P less than 0.05). During HCl perfusion, peristaltic amplitude and duration increased slightly, and peristaltic velocity slightly decreased similarly in both groups. There was no difference in the incidence of nonpropagated, segmental, or swallow-initiated simultaneous contractions, or change in resting intraesophageal pressure during HCl perfusion in control and GERD groups. This study identified abnormal contractile amplitude as a specific defect in the primary peristaltic wave of esophagitis patients but does not support a role for acid-induced motility changes in the generation of symptoms in GERD.

Rapid, small-scale preparation of gastrointestinal hormones by high-performance liquid chromatography on a C 18 column

A rapid reversed-phase high-performance liquid chromatography method was developed for the isolation of small quantities of biologically active gastrointestinal hormones, using a Varian MCH-10 C 18 column. Biologically active secretin was isolated from contamination with other hormones, including cholecystokinin, gastrin, motilin, and vasoactive intestinal polypeptide, from samples of the acid perfusate of canine duodenum and from the crude acetic acid extract of canine antral mucosa containing less than 100 picomoles of secretin. The method also appeared to be suitable for the isolation of cholecystokinin octapeptide and motilin.

Are Esophageal Motility Abnormalities Produced During the Intraesophageal Acid Perfusion Test?

Many years ago, it was proposed that the symptoms of heartburn correlated more closely with acid-induced esophageal motility abnormalities than with the presence of inflammation. This concept, however, has not been evaluated by modern manometric techniques. We monitored intraesophageal pressures during acid perfusion (O.1N hydrochloric acid) in 17 reflux patients with gross esophagitis and positive pain response and 17 age-matched controls. Using a low-compliance infusion system, amplitude, duration, velocity, and the presence of simultaneous and repetitive contractions in the body of the esophagus were evaluated. Amplitude did not change in either group. Duration did increase significantly during acid perfusion in reflux patients, but not in controls. Mean duration between groups, however, was similar before and during acid perfusion. No simultaneous contractions were observed, while three patients and two controls had repetitive contractions. A significant decrease in velocity was observed in both groups during acid perfusion. These studies indicate that acid-induced motor abnormalities are neither a common accompaniment nor necessary for the production of acid-induced pain in the esophagus.

Are esophageal motility abnormalities produced during the intraesophageal acid perfusion test?

Are esophageal motility abnormalities produced during the intraesophageal acid perfusion test?

Effect of secretin on stress-induced gastric bleeding in rats.

The effect of secretin on gastric bleeding induced by water (20 degrees C) immersion stress was studied by means of either perfusion of hydrochloric acid (0.13 N) or instillation of hydrochloric acid solution (0.4 N) into the rat stomach. When the stomach was perfused with acid solution, gastric bleeding occurred 20 min after the stress of water immersion and the amount of bleeding increased with time. It was found that integrated amounts of gastric bleeding after stress were more significantly decreased in the secretin-treated group (7.5 clinical units/kg/hr) than the saline control. On the other hand, intraduodenal administration of cimetidine (100 mg/kg) or propantheline (30 mg/kg) did not affect gastric bleeding. It was also revealed that the total amount of glycoprotein in the 4-hr perfusate was decreased 30% by the water immersion, but that secretin treatment prevented the 30% decrease in glycoprotein in the perfusate. In experiments on intragastric instillation of hydrochloric acid solution, it was found that gastric bleeding was seen only when the concentration of hydrochloric acid solution was higher than 0.4 N. However, the bleeding was also significantly prevented by treatment with secretin (2.5 and 7.5 clinical units/kg/hr). In conclusion, secretin prevents stress-induced gastric bleeding at least in part by increasing glycoprotein secretion in the gastric mucosa in the rat.

Oesophageal motor events at the occurrence of acid reflux and during endogenous acid exposure in healthy subjects and in patients with oesophagitis.

In order to assess the oesophageal motor events associated with the occurrence of gastro-oesophageal acid reflux and those during endogenous acid exposure, we studied six healthy subjects and nine patients with symptoms and lesions of reflux oesophagitis. In the case of each subject simultaneous pressure and pH measurements of the distal oesophagus were taken both in fasting conditions and after a standardised balanced meal. Reflux episodes occurred in the absence of a lower oesophageal sphincter relaxation (34.3%, 17.7%) or in the presence of a relaxation associated (34.2%, 30.8%) or unassociated (31.5%, 51.5%) with a peristaltic sequence, in the controls and patients respectively. No significant differences were found between the two groups. During endogenous acid perfusion the distal oesophagus showed mainly a peristaltic motor activity, but the mean hourly number of peristaltic sequences was significantly lower in the patients than in the controls (33.5 +/- 27.2 vs 81.5 +/- 3.2, p less than 0.01). Our results show that the mechanisms of reflux are similar in controls and in patients, while the peristaltic frequency is reduced in the latter. This motor failure may be responsible for the increased reflux duration observed in patients with oesophagitis.

Acid instillation increases gastric luminal prostaglandin E2 output in man.

The capacity of the gastroduodenal mucosa to maintain integrity when exposed to acid and pepsin may require formation of endogenous prostaglandins (PG). The gastric mucosa is capable of PG biosynthesis, and PGE2 is present in the gastric contents of man. The purpose of this study was to examine if acidification of the human stomach affects the output of PGE2. Gastric perfusion was made with 150 mM HCl in seven healthy subjects pretreated with a histamine-2-receptor blocker (ranitidine). Gastric luminal PGE2 was measured by gas chromatography-mass spectrometry. Basal output of PGE2 was 1.42 +/- 0.24 pmol/min (mean + SEM), which increased to 5.37 +/- 0.91 pmol/min (p less than 0.02) during acid perfusion. Gastric acidification did not cause mucosal damage as judged by luminal DNA. We conclude that PGE2 is synthesized in the gastric mucosa even during nearly complete inhibition of parietal cell secretion. Luminal acid, a likely physiological stimulator of mucosal defense, induces a fivefold increase in PGE2 output from the intact mucosa.

Oesophageal motility during acid-provoked heartburn and chest pain.

Oesophageal motility was studied in 59 patients before and again after prolonged acid perfusion. In group 1 (n = 16), who were asymptomatic during the acid perfusion, no significant motility differences were obtained by perfusion. In group 2 (n = 18), who had heartburn, and in group 3 (n = 25), who had angina-like chest pain during acid perfusion, significant (p less than 0.01-0.001) changes of motility were seen: these included higher peristaltic amplitude, longer contraction duration, and slower peristaltic velocity. In addition, patients in group 3 showed a decrease (p less than 0.01) of peristaltic propagation and had secondary wave activity more often (p less than 0.01) during acid perfusion. Significantly (p less than 0.01) more patients in group 3 showed secondary wave activity after acid perfusion than in group 2. Pretest motility investigation did not separate the two acid-sensitive groups from the acid-unsensitive one, whereas the investigation of the lower oesophageal sphincter (LOS) did. Thus, LOS incompetence was significantly (p less than 0.01) commoner in the two symptomatic groups than in the asymptomatic group. We suggest that the motility changes observed during acid perfusion are secondary to increased sensory stimulation from the oesophagus but are not the cause of the symptoms. However, nervous reflex reactions from other chest organs, such as the heart, may also explain the results.

An energy-dependent step in aminoglycoside ototoxicity: prevention of gentamicin ototoxicity during reduced endolymphatic potential.

Guinea pigs received a bolus of gentamicin (10 mM for 5 min) by perilymphatic perfusion which normally led to an irreversible loss of the cochlear microphonic potential (CM). Various experimental conditions that reduced the endolymphatic potential (EP) were then superimposed on the gentamicin application. Reversible reductions in EP (and, concomitantly, in CM) were induced by asphyxia (3 min), intravenous furosemide (50 mg/kg), and perilymphatic perfusion of aminooxyacetic acid (10 mM). When the administration of gentamicin was initiated at the time of maximal EP reduction the usual irreversible gentamicin-induced decline of CM was prevented. The results indicate that a metabolic process is essential in the expression of gentamicin toxicity. The data are consistent with the inhibition of an energy-dependent transport of the aminoglycoside. Alternatively, the data are also compatible with the hypothesis that entry of gentamicin into hair cells is prevented by a reduction in their transmembrane electrical potential.

Impairment of Vagal Function in Reflux Oesophagitis

Autonomic nervous function in reflux oesophagitis was assessed by measuring the response of the lower oesophageal sphincter to abdominal compression, gastric secretory response to insulin-induced hypoglycaemia and pulse rate variability with respiration. Rise in intra-abdominal pressure normally causes an increase in lower oesophageal sphincter pressure through a vagally mediated mechanism. In 59 of 83 patients with reflux oesophagitis the sphincter response was subnormal, and this was commoner in older patients but was unrelated to the presence of a hiatal hernia. During oesophageal acid perfusion, the onset of pain, but not that of disordered motility, was delayed in those with an abnormal sphincter response suggesting impairment of afferent autonomic function. Efferent gastric vagal function, assessed by the gastric secretory response to insulin induced hypoglycaemia and expressed as a ratio of the maximal acid output after pentagastrin, was subnormal in 15 of 27 patients with reflux oesophagitis. Pulse rate variability with deep respiration, an indicator of one aspect of non-alimentary vagal function, was subnormal in 18 of 62 patients with reflux oesophagitis. There was no correlation between abnormalities in these three tests of vagal function or with the severity of oesophagitis. These findings suggest that vagal impairment is common in reflux oesophagitis. As impairment of vagal function is not confined to the alimentary system it is unlikely to be simply a consequence of reflux oesophagitis and may be important in the pathogenesis of gastro-oesophageal reflux.

Effect of luminal pH and HCO3- on phosphate reabsorption in the rabbit proximal convoluted tubule.

Luminal pH in the proximal convoluted tubule may alter phosphate reabsorption in a variety of acid-base disturbances and in normal conditions as luminal pH decreases along the length of the proximal tubule. These studies address the influence of luminal pH on phosphate reabsorption in isolated perfused proximal convoluted tubules from normal rabbits. Initial perfusates were either pH 6.2 or 7.4, and the bath pH was 7.4. All solutions contained 10 mM total phosphate. The first experiments used HCO3-/CO2-free solutions to examine the effect of luminal pH independent of changes in [HCO3-] or Pco2. Lumen-to-bath phosphate flux increased from 0.63 +/- 0.23 with alkaline perfusate to 2.04 +/- 0.35 pmol X mm-1 X min-1 with acid perfusate. In a separate group of tubules, acetazolamide had no qualitative effect on this result. With HCO3-/CO2-containing solutions, phosphate reabsorption increased from 4.53 +/- 1.46 with alkaline perfusate to 9.67 +/- 1.77 pmol X mm-1 X min-1 with acid perfusate. Thus, an acid luminal fluid can enhance proximal phosphate reabsorption independent of the presence or absence of HCO3-/CO2. To examine the specificity of this effect, the influence of luminal pH on another solute (glucose), reabsorbed via a Na+-coupled mechanism, was studied. Lumen-to-bath glucose flux increased in the same direction: from 52.78 +/- 4.91 with alkaline perfusate to 57.13 +/- 4.70 pmol X mm-1 X min-1 with acid perfusate. The mechanism of the influence of luminal pH on phosphate and glucose reabsorption is not explained but could be direct or indirect from changes in intracellular pH, Na+ activity, metabolism, or basolateral transport. Since an acid luminal pH is expected to inhibit or decrease Na+-H+ exchange at the luminal membrane, these results are also consistent with a competition for the available Na+ gradient between phosphate and glucose transport and the Na+-H+ exchanger in the proximal tubule.

Effects of acute experimental esophagitis on mechanical properties of the lower esophageal sphincter

The mechanical properties of the cat lower esophageal sphincter (LES) circular muscle were studied in untreated animals and in cats that had biopsyproven esophagitis induced by 30-min perfusions of 0.1 N HCl 5 cm above the LES on four consecutive days. The location of the in vivo LES was identified by the pull-through method with a pressure measuring probe. Consecutive rings were cut from the LES and esophagus and tested in vitro. Force-length curves were obtained in standard Tyrode solution, in Tyrode solution with 140 mM KCl, and in Ca-free Tyrode solution with 5 mM ethylenediaminetetraacetic acid to determine basal, total, and passive forces, respectively. The active force was measured as the difference between the total and passive forces, whereas the basal-active force was measured as the difference between the basal and passive forces. In the untreated animals, LES rings exhibited the steepest basal force—length curve and the highest active and total forces under maximal KCl stimulation. The passive force of the LES rings was equal to that of the esophageal body rings. Basal in vitro forces were significantly reduced in all acid-perfused animals, whereas the passive forces were not affected. Active and basal-active forces were also significantly reduced. The maximum active force developed by LES rings was reduced, whereas esophageal rings, four rings proximal to the ring corresponding to the high pressure point, were not affected. The reduction in LES active force was related to the intensity of histologic damage, whereas basal-active forces were uniformly reduced. This study shows that in vitro mechanical properties of the LES are affected by induction of esophagitis and suggests that the ability to develop tonus in the basal state is reduced by acid perfusion, even in animals in which the ability to develop active contraction in response to maximal KCl stimulation is preserved. The response to KCl is reduced only by more extensive histologic damage.

Central-peripheral chemoreceptor interaction in awake cerebrospinal fluid-perfused goats.

We assessed the ventilatory interaction between central [central nervous system (CNS)] and peripheral chemoreceptor stimuli in five awake goats. CNS extracellular fluid (ECF) [H+] was altered with cisterna magna perfusion of mock CSF. Peripheral chemoreceptors were stimulated with three doses of NaCN given intravenously. The resulting dose-response curves were used to assess interaction of the central and peripheral stimuli. The observed interaction was hypoadditive; i.e., the average slope of the NaCN-inspired minute ventilation dose-response line was significantly greater during alkaline perfusion than during acidic perfusion. This correlation can be described by slope = -0.24 (CSF [H+]) + 30.7; r = 0.67 (P less than 0.01). Increased ventilatory responses were accompanied by increases in mean inspiratory flow, tidal volume, and breathing frequency and decreases in expiratory time in response to peripheral chemoreceptor stimulation. Unlike previous reports in anesthetized and denervated animals, in our awake intact goats the ventilatory and tidal volume responses showed no significant dependence on the level of control (pre-NaCN stimulus) inspired minute ventilation. We conclude that the level of [H+] in cerebral ECF exerts a significant reflex-mediated hypoadditive effect on the ventilatory responses to peripheral chemoreceptor stimulation.

Plasma secretin and pancreatic response to various stimulants including a meal.

In dogs with gastric and duodenal Thomas cannulas, we investigated the threshold dose range of exogenous secretin and intraduodenal HCl for pancreatic bicarbonate secretion and, with a recently developed radioimmunoassay, measured the increase in plasma secretin concentrations. Synthetic secretin (2.5, 7.5, and 22.5 ng X kg-1 X h-1) was dissolved in saline or 0.1% dog albumin and given with or without a background infusion of 30 ng X kg-1 X h-1 of caerulein. The minimal dose of secretin that elicited a significant pancreatic bicarbonate response as well as an increase in plasma secretin concentration was 7.5 ng X kg-1 X h-1 when administered with albumin and 22.5 ng X kg-1 X h-1 without albumin. The threshold dose for duodenal HCl was 2 mmol X h-1. The threshold secretin dose for bicarbonate secretion and for an increase in plasma secretin levels was unchanged with a background caerulein infusion. Furthermore, postprandial secretin concentrations were measured. After a meat meal plasma secretin release appeared to occur in spikes up to 10 pmol X l-1 corresponding to secretin levels seen during infusion of 7.5 ng X kg-1 X h-1 of secretin and intraduodenal acid perfusion at a dose of 2 mmol X h-1.

Coronary sinus lactate estimation and esophageal motor anomalies in angina with normal coronary angiogram.

Twenty-three patients (ages 44-82) with angina-like chest pain with a negative stress test and a normal coronary angiogram were studied for myocardial lactate metabolism during atrial pacing and for esophageal motor function with manometric measurements and acid infusion test. Eight patients had an abnormal myocardial lactate metabolism during maximal atrial pacing. Esophageal motor anomalies were observed in six of these eight patients and nine of the 15 subjects with normal myocardial lactate metabolism. The frequency and type of these anomalies were not different between the two groups of patients. Perfusion of acid into the esophagus reproduced the spontaneous pain syndrome in three patients, independent of any simultaneous motor dysfunction. These results suggest that esophageal motor anomalies must be interpreted with caution in patients with angina-like chest pain before affirming the exclusively esophageal origin of the pain.

Further studies of organic base secretion by rabbit proximal tubules.

The aim of the present studies was to further characterize the mechanisms responsible for the secretion of the organic base procainamide by measuring [3H] procainamide transport in superficial (SF) and juxtamedullary (JM) S2 segments of rabbit proximal tubules perfused in vitro. When perfusate pH was changed from 7.4 to 6.2, procainamide secretion increased by 227% in SF and by 159% in JM tubules. In the presence of ouabain the acidic perfusate caused only a minimal increase in procainamide secretion. When the perfusate pH was increased, procainamide secretion was reduced. Acetazolamide, 10(-5) M in the bath, reduced procainamide secretion in both SF and JM tubules. In SF tubules amiloride, 10(-4) M in the perfusate, inhibited procainamide secretion, whereas nonradioactive procainamide, quinidine, and cimetidine did not. When ambient sodium was reduced to 10 mM, the rate of procainamide secretion was low and was not affected by amiloride in the perfusate or acetazolamide in the bath. Amiloride in the bath caused a dose-related inhibition of procainamide secretion. The rate of procainamide secretion by cortical collecting tubules was very low and was not affected by acetazolamide. The mechanisms of renal organic base secretion are complex. Some of the present data are consistent with a mechanism involving organic base-proton exchange across the apical cell membrane. However, other data are not consistent with this being the major mechanism involved.

Solid bolus transit by esophageal scintigraphy in patients with dysphagia and normal manometry and radiography.

Scintigraphic technique was used to study esophageal transport of a solid bolus in 16 patients with dysphagia but with normal manometry, and negative acid perfusion tests, acid clearing tests, and pH reflux tests. Radiology performed on 14 of the 16 patients showed no evidence of organic lesions. Half the patients had abnormal findings at scintigraphy, with either bolus retention in the upper part of the esophagus or prolonged transit time as compared to a group of 20 asymptomatic subjects. Scintigraphy can be regarded as a valuable complement in the objective documentation of dysphagia when other diagnostic methods fail.