An improved radioenzymatic assay for histamine in human plasma, whole blood, urine, and gastric juice

Radio-enzymatic determination of histamine: interference by fluoride and possible activation of histamine methyl transferase

The reproducibility of a radio-enzymatic method for determining plasma histamine was found to be affected by the anti-coagulant used for collecting blood. Recovery experiments from whole blood indicated that heparin yielded values that were more accurate than with EDTA or sodium fluoride; fluoride gave a mean value which was +41% higher than with heparin (P=0.054). Addition of fluoride to a standard calibration curve, and of increasing amounts to aliquots of 5 ng histamine also yielded higher values than in controls, up to +15% (P<0.1) and +14.1% (P=0.03) respectively. Fluoride did not affect the detecting system and was not contaminated with histamine; nor did it breakdown the methyl donor, S-adenosyl-L-methionine. It is concluded that heparin is the anti-coagulant of choice and that fluoride may activate histamine methyl transferase from pig brain. Fluoride may possibly have a biological role as an enzyme-activator and a usefulness in the therapy of mastocytosis.

Markers of mast cell degranulation

Mast cells are the primary effector cells of immediate hypersensitivity reactions in humans. Upon mast cell activation both preformed and newly synthesized mediators are secreted. Histamine can be measured by fluorometric assays, radioenzymatic assays, and immunoassays. These methods have been applied to plasma and urine to detect histamine that had been released in vivo and to release histamine in vitro from basophils and mast cells. Another mast cell constituent is tryptase, which is a more selective marker of mast cells, because negligible amounts are found in basophils. beta-Tryptase is stored in secretory granules and is actively released when mast cells degranulate. alpha-Protryptase remains in the proenzyme form and is constitutively released from mast cells, and consequently its level in serum reflects total numbers of mast cells. alpha-Protryptase levels are elevated in serum at baseline in subjects with systemic mastocytosis, whereas beta-tryptase is elevated in serum from subjects with systemic anaphylaxis. These markers serve as precise clinical indicators of the involvement of mast cells in human disease.

High-performance liquid chromatographic method for the evaluation of possible interferences in basophil-histamine release measurements

Basophil activation studies commonly rely on the measurement of histamine following extraction and condensation to o-phthalaldehyde (OPT) as a quantitative measurement of degranulation. Specificity has long been recognized as a problem with this method. We have described a new high-performance liquid chromatographic method that allows for both a qualitative and a quantitative check of the purity of the OPT-histamine adduct. This method was sensitive (limit of detection = 2.55 pmol) and linear over a wide range (5 to 1000 ng/ml).

Determination of histamine in human plasma: the European external quality control study 1988

There is an increasing interest in measuring human plasma histamine levels in various clinical conditions. A variety of 'old' and newly developed techniques are applied to meet this demand. However, the discrepancy between reported reference values for histamine in human plasma measured using this variety of techniques, suggests the existence of a certain degree of inaccuracy and imprecision. We therefore organized an external quality control study on the reliability of current histamine determinations in European laboratories. Three lyophilized plasma quality control samples, in duplicate, covering the normal and pathological range of histamine concentrations (0-45 nmol/l), two different aqueous histamine standard samples and one solvent sample were sent to 10 laboratories for the analysis of their histamine content. The following methods were used: gas chromatography-mass spectrometry (n = 2), enzymatic single isotopic assay (n = 1), fluorometric-fluoroenzymatic assay (n = 3), radioimmunoassay (n = 3) and high performance liquid chromatography (n = 2). The study was performed and evaluated according to the approved recommendations (1983) of the International Federation of Clinical Chemistry (IFCC). The target values +/- s.d. of the three plasma samples were: 39.5 +/- 4.6 nmol/l (CV = 11.6%), 2.3 +/- 2.2 nmol/l (CV = 96%) and 8.9 +/- 1.5 nmol/l (CV = 17%), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of urinary histamine by a new radioenzymatic assay: documentation of assay specificity and establishment of normal excretion rates

The goals of this study were to evaluate the specificity of a new radioenzymatic assay for histamine when it is used for urinary-histamine determinations and to establish normal rates of urinary-histamine excretion for male and female subjects. Specificity of the assay was characterized by reacting urine samples at two different incubation temperatures and with varying amounts of highly purified histamine N-methyltransferase and S-adenosyl-L-[methyl-3H]methionine. The radiolabeled products were then separated by thin-layer chromatography and visualized by fluorescence-enhanced autoradiography. Our results indicate that at least one other substrate for histamine N-methyltransferase in addition to histamine is present in human urine, although the identity of this compound could not be determined. Optimization of enzyme-reaction conditions eliminated the methylation of this unidentified substrate while the methylation of histamine was maintained. The average urinary unidentified substrate while the methylation of histamine was maintained. The average urinary excretion of histamine determined for male subjects (N = 37) and female subjects (N = 111) was 18.7 micrograms/24 hr and 27.3 micrograms/24 hr, respectively. More than 12% of the normal female subjects examined had urinary-histamine excretion rates in excess of 50 micrograms/24 hr, which overlaps into the range previously considered to be indicative of abnormal mast cell secretion. In summary, this is the first radioenzymatic assay for histamine with documented specificity for the measurement of histamine in human urine.

Kinetic analysis of the histamine N-methyltransferase reaction as used in the histamine radioenzymatic assay: optimization of assay specificity

The specificity of the histamine N-methyltransferase (HNMT) based radioenzymatic assay for histamine has been questioned since N-alpha-methylhistamine is also a substrate for this enzyme. Purification of HNMT for use in the radioenzymatic assay improves sensitivity and specificity of this procedure. In this investigation, further improvements in specificity, with respect to other HNMT substrates, were attained by optimization of reaction conditions based on the evaluation of HNMT kinetic parameters. These studies demonstrate that appropriate control of reaction temperature and concentration of both the enzyme and the radiolabeled methyl donor improve the specificity of this assay for histamine.

Systemic mastocytosis in a 5-year-old child: successful treatment with disodium cromoglycate

Most clinical signs and symptoms of systemic mastocytosis (SM) are attributed to histamine release. We report here a 5-year-old male child with SM, who suffered from the age of 4 months from disseminated skin lesions, vomiting, diarrhoea, abdominal pain, flushing, tachycardia, hypotension, somnolence, and transient blindness, triggered by heat and egg ingestion. Oral disodium cromoglycate (DSCG) or placebo were started in a single blind trial at a dose of 100 mg/kg/day in four divided doses. The child was studied for 21 months during the administration of three courses of DSCG, each of 6 months' duration, interspersed with three 1-month courses of placebo. During treatment with DSCG all the systemic manifestations improved, and the histaminaemia decreased. During the placebo periods the symptoms, signs, and histaminaemia recurred.

A comparison of the available methods for the measurement of histamine in sputum

Sputum samples from patients with chronic bronchitis were assayed for histamine content using a bioassay, and/or fluorometric assay and single or double radioenzymatic techniques. Comparison showed that all the assays produced significant differences in the measurement of sputum histamine. Similarly, it was observed that the assays all showed significant differences in the measurement of histamine released from human basophils. In general the fluorometric assay give the highest values for histamine in sputum and the double-isotope radioenzymatic assay the lowest. In contrast, no differences were found between the bioassay, fluorometric assay and the single-isotope radioenzymatic assay for the measurement of histamine added to Tyrode's solution. These results suggest that in biological samples some of the assays may additionally be measuring metabolites of histamine or other components present in the samples and underline the need to measure the levels of histamine and its metabolites separately in sputum.

Plasma histamine in asthmatic and control subjects following exercise: influence of circulating basophils and different assay techniques

Arterial plasma histamine concentrations were measured after exercise in 10 subjects with extrinsic atopic asthma, 10 who were non-atopic and non-asthmatic and seven who were atopic but non-asthmatic, by a single isotope radioenzymatic assay. Significantly higher plasma histamine concentrations were found in the asthmatic subjects before exercise than in the non-atopic controls (p less than 0.05). The mean histamine concentration rose after exercise in all groups but the increased levels were not significantly different from pre-exercise values. Similarly, mean circulating basophil counts increased in all groups after exercise, and a highly significant correlation was found between basophil counts and whole blood histamine concentrations (p less than 0.001). In vitro studies showed that there was a significant correlation between the number of basophils added to plasma samples and the concentrations of histamine subsequently detected. Although the mean concentrations of plasma histamine and whole blood histamine and number of basophils in the atopic control group were intermediate between those found in the atopic asthmatic and non-atopic controls, none of the differences was significant. Venous plasma histamine concentrations after exercise were measured in a further five subjects with extrinsic atopic asthma and five non-atopic, non-asthmatic subjects before and after exercise with the more sensitive and specific double isotope radioenzymatic assay. Concentrations of plasma histamine measured by this assay were about one tenth of those measured by the single isotope radioenzymatic assay. Although a small rise in mean plasma histamine concentration occurred in both groups after exercise there was no significant difference in these levels either between or within the groups. We find no evidence from these studies on measurement of peripheral blood histamine to support the hypothesis that mast cell mediator release is implicated in the pathogenesis of exercise induced asthma.

A new radioenzymatic assay for histamine using purified histamine N-methyltransferase

Radioenzymatic assays for histamine (Hm) have found wide application. However, these procedures may lack the sensitivity necessary to quantify Hm in certain biological samples, such as human plasma. Purification of histamine N-methyltransferase (HNMT) has permitted the development of a new and highly sensitive radioenzymatic assay for Hm. HNMT was purified by sequential ion exchange, hydrophobic and molecular exclusion chromatography. The use of purified HNMT in the Hm assay has allowed the inclusion of high specific activity tritiated S-adenosyl-L-methionine ([3H]SAME) and the development of a simplified solvent extraction product isolation procedure. This assay has a sensitivity of approximately 2 picograms and is specific for Hm. Hm was easily quantified in human plasma and was found to be 303 +/- 81 pg/ml (mean +/- SD) in 8 male subjects. Substantial blank reduction and increased product conversion occur when purified HNMT is utilized in the Hm radioenzymatic assay, thus, increasing the sensitivity and possibly improving the specificity of this procedure.

Measurement of tele-methylhistamine and histamine in human cerebrospinal fluid, urine, and plasma

A gas chromatographic-mass spectrometric method described by us to measure tele-methylhistamine (t-MH) in brain was used to measure t-MH in human cerebrospinal fluid (CSF), urine and plasma. The presence of t-MH in these body fluids was rigorously established. No pros-methyl-histamine could be detected, and it was used as internal standard to quantify t-MH in the fluids. The mean levels of t-MH were: urine, 943 pmol/mg creatinine; plasma, 12.3 pmol/ml; and CSF, 2.2 pmol/ml. Parallel measurements of histamine by a radioenzymatic method showed, respectively, 182 pmol/mg creatinine; 19.5 pmol/ml; and 388 pmol/ml. The levels of HA in CSF, much higher than those of its metabolite, t-MH, are high enough to stimulate HA receptors in the central nervous system.

Histamine, neutrophil chemotactic factor and circulating basophil levels following exercise in asthmatic and control subjects

Significant increase in the maximum post-exercise values of plasma histamine (PH), whole blood histamine (WBH) and neutrophil chemotactic factor (NCF) occurred in arterial blood within the first hour after exercise in asthmatic patients. However, similar changes in PH and WBH also occurred in the control group. Significant increases in circulating basophil counts following exercise were found in both groups, which closely mirrored the changes in PH and NCF, and there was a highly significant correlation between rises in WBH and basophil counts (P less than 0.001). When plasma histamine as assayed in venous blood using a more sensitive and specific double isotope radio enzymatic assay no significant alteration in plasma histamine levels was detected in either the asthmatic or the control group. We conclude that there is no evidence from these studies to support the suggestion that mast cell mediator release is involved in the pathogenesis of exercise-induced asthma, and that any observed changes in levels of PH and NCF after exercise may be related to changes in levels of circulating basophils.

Histamine and some of its metabolites in human body fluids

The concentrations of histamine, t-methylhistamine and t-methylimidazoleacetic acid were measured in human cerebrospinal fluid, plasma and urine, Especially noteworthy are the levels of histamine in cerebrospinal fluid which are far higher than those of t-methylhistamine and of t-methylimidazoleacetic acid, and high enough to stimulate histamine receptors in the central nervous system. It is suggested that mast cells, which surround the subarachnoid space, may contribute histamine to the cerebrospinal fluid and may offer a target for drugs and for immunologic actions. The t-methylhistamine and t-methylimidazoleacetic acid levels in cerebrospinal fluid may reflect central histaminergic activity, although a source of these metabolites in addition to histamine needs to be considered.

The demonstration of histamine release in clinical conditions: a review of past and present assay procedures

Topics related to the measurement of histamine in human plasma and other body fluids are reviewed. These include (1) an overview of the data obtained by the biological, fluorometric and radioenzymatic assays over the past 45 years; (2) the various modifications of the radioenzymatic isotopic assay of histamine and the development of a single extraction step assay; (3) a compilation of values obtained in our laboratory by the radioenzymatic assay of histamine levels in various body fluids in disease states associated with abnormal histamine production or release; and (4) factors that affect histamine levels in plasma and some experimental considerations for monitoring changes in free histamine levels. The last topic includes a discussion of the halflife of histamine in the circulation, its clearance across various vascular beds, and the fact that capillary endothelial cells are one site of inactivation of circulating histamine.

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

Histamine assays can be unreliable in individual subjects or samples even though the particular method is in general working very well. Therefore the specificity and accuracy of histamine determination in the gastric aspirate of individual duodenal ulcer patients was thoroughly examined and shown to be satisfactory. Pitfalls of the fluorometric assay were investigated. A native (non-histamine) fluorescence in gastric aspirate which occurs before the addition of OPT was not removed by the original Shore procedure. In the combined assay (Dowex 50 + butanol extraction) this fluorescence no longer interferes with the assay. For the identification of histamine in a single gastric aspirate of an individual duodenal ulcer patient, the reversed blank (3 M HCl added to the reaction mixture before OPT instead after OPT), excitation and fluorescence spectra, the heating test with spectra recorded and the HMT test were found to be reliable. The formaldehyde test and the heating test without recording the spectra were useless since they gave false negative results. Since the HMT test was regarded as a reference method it was thoroughly investigated both by theoretical considerations (enzyme kinetics) and by a series of measurements in a single patient as well as in a group of nine subjects. Samples from the period of peak acid output in response to pentagastrin showed an average histamine concentration of about 8 ng/ml and a histamine output of 1.5 microgram/30 min.

[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.