Assay and identification of histamine in human gastric aspirate by a fluorometric--fluoroenzymatic technique. Its application in patients with chronic duodenal ulcer

Comparison of the effects of histamine and N(alpha)-methylhistamine on neuronal function in the guinea-pig oesophagus and ileum

The effects of histamine and N(alpha)-methylhistamine, two components of gastric juice, on vagal and transmural stimulation of the guinea-pig isolated oesophagus were compared with their effects on cholinergic and on non-adrenergic-non-cholinergic (NANC) neuronal responses in the isolated ileum, both tissues having been pretreated with mepyramine (1 microM). Histamine (< or = 10 microM) and N(alpha)-methylhistamine (< or = 1 microM) had no significant effect on either vagal or transmural stimulation in the oesophagus. Substance P, which produces a contraction by activation of cholinergic nerves in the oesophagus also was unaffected by histamine. In contrast, the agonists inhibited contractions produced by cholinergic nerve stimulation in the ileum; the inhibition produced by histamine (10 microM) was up to 73 +/- 5%, that by N(alpha)-methylhistamine (1 microM), 48 +/- 5%. Histamine also inhibited responses to stimulation of NANC neurons by up to 37 +/- 14%. The effects of histamine and N(alpha)-methylhistamine in the ileum were inhibited by clobenpropit (0.1 microM). These findings suggest that histamine and N(alpha)-methylhistamine have no role in the modulation of neuronal function in the oesophagus, in contrast with their effect in the ileum.

Radioenzymatic assay for histamine: development and validation

Radioenzymatic assays are sensitive analytic tools that use an enzyme to quantify a substrate for that enzyme. Purified histamine N-methyltransferase has been used as the basis for an assay for histamine. The sensitivity of the procedure is less than 10 fmol. The specificity of the assay is increased when the transferase reaction is carried out at 0-3 degrees C. Data documenting the precision of the assay, the stability of histamine in human plasma, and the gastric secretory rate of histamine are presented along with a chronologic description of the development of the technique.

Reliability and practicability of the fluorometric-fluoroenzymatic histamine determination in pathogenetic studies on peptic ulcer: detection limits and problems with specificity

Histamine, among various "biologic-physiologic" abnormalities, is considered as a pathogenetic factor in chronic duodenal ulcer disease. The 10-30 per cent difference between its concentration in gastric and duodenal mucosa of patients compared to healthy controls, however, has to be demonstrated to be specific for the disease. It has to be shown to be neither a methodological artefact nor a common effect, concomitant factor or consequence. This study, after a series of pathogenetic trials examines systematic errors (biases) in the fluorometric-fluoroenzymatic histamine assay under the conditions of field studies including tests on specificity over a time period of 10 years. It concentrates on sensitivity (detection limits) and specificity of a standard technique described herein. A modified Shore procedure for large scale assays in human biopsies was developed including reference luminescence values for all reagents, cleaning material and glassware, reduction of OPD concentration to 0.05%, purification of n-heptan, omission of centrifugation steps in the extraction procedure and use of 2 ml 1 M HClO4 in the homogenization step to prevent losses of histamine due to adherence to the mechanical homogenizer. This assay was sensitive enough to measure histamine without difficulty in any biopsy taken. The detection limit was 3 ng/biopsy, but the smallest quantities of the amine ever obtained were 10.6 and 18.3 ng/biopsy (depending on both histamine content and biopsy weight). A series of problems had to be solved both in achieving and demonstrating specificity. It had to be defined not only for the assay in general, but also for assessing the difference in histamine content between ulcer patients and healthy controls. Exogenous more than endogenous fluorescing material interfering with the determination had to be excluded. A series of pitfalls were detected which had to be overcome in demonstrating the specificity of the assay by physicochemical and enzymatic tests. The specificity of the identification tests was more often impaired than the histamine assay itself. Fluorescing material interfering with the assay occurred in the homogenization, extraction and condensation steps, was found in water, OPD, the organic solvents, the cleaning material and in all kinds of plastic vessels. Plasticizers were shown by physicochemical characteristics including fluorescence spectra to be most likely responsible for this interfering material. Rules were developed to exclude such hazards in specificity in longterm pathobiochemical studies. Enzymatic identification test were applied to exclude endogenous fluorecing substances interfering with the standard technique. Simil

Effects of a mast cell stabiliser (FPL 52694) on human gastric secretion

The effects of a new monochrome mast cell stabilizer (FPL 52694) on gastric secretion have been studied in healthy volunteers. When administered orally for 3 days, FPL 52694 consistently reduced nocturnal and pentagastrin-stimulated secretion of acid by about 50%. Meal-stimulated gastric secretion was not affected by the drug. Inhibition of the gastric secretory response to pentagastrin was not significant when single doses of the drug were administered either into the stomach or the duodenum, but administration of multiple doses resulted in significant inhibition. The drug does not inhibit gastric secretion by injuring the gastric mucosa, since the gastric mucosal barrier to back diffusion of hydrogen ions is not affected. We conclude that this mast cell stabilizer provides an interesting tool for studying aspects of the physiological control of gastric secretion and may have a therapeutic role in peptic ulceration.

Two biochemically distinct populations of histaminocytes separated by isokinetic sedimentation of dispersed rat gastric cells

Two populations of histaminocytes, with different sedimentation rates (SR), were separated by a computer developed isokinetic gradient using dispersed rat gastric mucosal cells. Histamine content, histidine decarboxylase (HDC) activity and incorporation of radiolabelled histidine metabolites were used to assess the migration of specific cells throughout the gradients. One histaminocyte population, with cells of lower SR, contained high HDC activity and undetectable levels of histamine, whereas the other population, with cells of higher SR, contained lower HDC activity and high concentration of histamine. Both types of histaminocytes incorporated 3H-histidine metabolites. Electron microscopy showed that the fractions containing histaminocytes with lower SR had 3.5 times more endocrine ECL cells than the original population of dispersed fundic cells and lacked A and D cells, whereas the fractions with histaminocytes of higher SR were associated with a 2.7 times higher concentration of A and D cells and with a 7.7 times higher ratio of a variety of partial cells with a distinct mitochondrial morphology. These results are consistent with prior novel information regarding the separation of two populations of rat histaminocytes using different sedimentation techniques.

Is pentagastrin-stimulated secretion mediated by histamine?

Patients with duodenal ulcer disease received either a two hour pentagastrin infusion test or a similar test with the addition of a bolus of cimetidine, 200 mg, after one hour of pentagastrin. Pentagastrin induced secretion of acid and histamine, the secretion patterns of the two being similar. Total histamine output in the gastric aspirate in the first hour of pentagastrin infusion was related to total acid output (r = 0.58, p less than 0.01). A similar correlation was observed during the second hour of pentagastrin infusion (r = 0.61, p less than 0.05). Plasma histamine concentration rose to a peak coinciding with maximal acid secretion. After cimetidine blockade, gastric acid fell rapidly but gastric histamine output did not change. Plasma histamine concentration increased further. These results suggest that pentagastrin induced gastric histamine release is not affected by an acid inhibiting dose of cimetidine. Cimetidine caused histamine release into the circulation in both healthy volunteers and patients after total gastrectomy. The rise in plasma histamine concentration, however, was transient. In contrast, during pentagastrin infusion, the plasma histamine concentration remained high. These data support the hypothesis that histamine release induced by pentagastrin is a major stimulant of gastric acid secretion.

Separation and characteristics of two histaminocytes from rat gastric mucosa

To determine the properties of rat gastric cells involved in histamine metabolism (histaminocytes), fundic mucosa was enzymatically dispersed prior to separation by sedimentation methods. The distribution of histamine content, histidine decarboxylase (HDC) activity and incorporation of radioactive histidine metabolites were used to determine the characteristics of various populations of gastric cells. All activities measured, as well as most of the dispersed gastric cells, occurred in a narrow range of density between 1.083 and 1.091 g/ml. Velocity sedimentation showed that two populations of histaminocytes can be distinguished. One population has a higher sedimentation rate, suggesting a larger size, contains histamine, HDC activity and incorporates radioactive metabolites. Another population, in fractions with lower sedimentation rates, contains little histamine, has a higher HDC activity than the previous population and also incorporates radiolabelled histidine metabolites. For the first time, two populations of viable histaminocytes have been separated that differ in their biochemical properties.

[Plasma histamine assay in anaphylactoid reactions of the anesthetized subject. Effects of collection methods and plasma preparation on measured histamine]

Plasma histamine assay in man is indicated for the diagnosis of histamine release, as well as the elucidation of the mechanisms of adverse drug reactions, and the identification of clinical situations in anaesthesia and surgery where a pathological plasma histamine level may occur. Normal and pathological plasma histamine levels vary considerably in the literature. Data from various studies, especially one involving 300 patients in Heidelberg (G.F.R.), allow us to define the normal range for human plasma histamine as 0-1.0 ng . ml-1 . Values greater than 1 ng . ml-1 have to be considered as pathological. The problems related to blood collection and plasma preparation are considered here. Any judgement concerning the method described in the test must take into consideration our long experience of 15 years with it, its reliability in clinical conditions, its practicability, its relatively low cost, and finally, the absence of radioisotopes.