Histamine Metabolism in Healthy Subjects before and during Treatment with Aminoguanidine

Diurnal variation of urinary histamine and 1-methylhistamine excretion in healthy children

In order to establish a noninvasive method of monitoring immediate hypersensitivity reactions in children, we studied the diurnal variation of urinary histamine and 1-methylhistamine excretion and the influence of food intake in a group of 14 healthy nonatopic children (aged 2-16 years). Histamine and 1-methylhistamine in spontaneous urine samples were determined by radioimmunoassay. Mean variation of 2-h intervals was much higher for urinary histamine than for 1-methylhistamine (45% of base-line level versus 24%). There was no circadian rhythm or influence of food intake. The short half-life of histamine released into blood circulation may be the main reason for the higher variation of histamine excretion. In children, urinary 1-methylhistamine is less influenced by diurnal variation and is therefore more suited to monitor immediate hypersensitivity reactions than urinary histamine itself.

In vivo catabolism of histamine in the human stomach

The importance of the stomach in the magnitude of excreted amounts of the major histamine metabolite in the urine was studied during total parenteral nutrition in five patients before and after total gastrectomy. In all subjects, a reduction in the 24-h urinary excretion of methylimidazoleacetic acid was observed. No corresponding effect was seen after an operation because of abdominal aortic aneurysm. In patients with duodenal ulcer disease and those submitted to a cholecystectomy because of cholecystolithiasis, we studied the catabolism of histamine in the stomach by injecting 14C-histamine directly into the portal vein and, simultaneously, 3H-histamine intra-arterially to the corpus fundus region of the stomach and subsequently determining the urinary excretion of 14C. 3H-histamine and their basic and acid metabolites, respectively. We found no apparent difference in the pattern of excreted 14C and 3H metabolites between the two patients groups, indicating that the catabolism of histamine in the stomach of patients with duodenal ulcer disease is similar to that in 'healthy' controls.

Urinary excretion of histamine, methylhistamine (1-MeHi) and methylimidazoleacetic acid (MeImAA) in mastocytosis: comparison of new HPLC methods with other present methods

New HPLC-methods for the determination of histamine, 1- MeHi and MeImAA in human urine were compared with methods presently at use in our laboratory, the enzymatic double-isotope assay for histamine, the DNFB-method for 1- MeHi and the semiquantitative estimation of MeImAA by thin layer chromatography (TLC). A fairly good agreement between the methods was obtained for the measurement of histamine and 1- MeHi , although there was a rather large random error probably due to poor precision of the present methods. The TLC-method for MeImAA used so far overestimated by about 20% the HPLC-values, probably due to inaccurate correction for recovery by the internal standard technique. There was found to be a strong correlation between the urinary excretion of 1- MeHi and MeImAA in mastocytosis patients and the molar ratio MeImAA /1- MeHi appeared significantly higher compared to normal controls and patients with chronic granulocytic leukemia indicating in general a more efficient histamine catabolism in mastocytosis.

Studies on histamine metabolism in mastocytosis

The urinary excretion of histamine and its main metabolite, 1-methyl-4-imidazoleacetic acid (MeImAA), was determined in 30 adult patients with the clinical diagnosis of urticaria pigmentosa (UP). Clinical and laboratory investigations including skin histology, bone marrow examination, and scintigraphy of the skeleton, liver, and spleen revealed systemic manifestations in 14 cases. Among the 16 cases with dermal proliferation of mast cells only 3 cases classified as telangiectasia macularis eruptiva perstans (TMEP). All patients with systemic mastocytosis and UP excreted increased amounts of MeImAA in the urine while normal amounts were found in 2 of the patients with TMEP. A significant correlation existed between MeImAA excretion and the extent of mast cell infiltration in skin and internal organs. No such correlation was found for urinary histamine. Urinary MeImAA but not histamine is therefore considered a useful indicator of systemic involvement by reflecting the size of the mast cell histamine pool. The main symptom of the patients was pruritus, which was moderate to severe in 17 and mild or absent in 13 cases. Gastrointestinal symptoms were present in 14 patients. However, there was no obvious correlation between the excretion of MeImAA and any of the symptoms recorded. Neither was the severity of pruritus correlated to the histamine content of the skin, which was measured in both lesional and unaffected skin in 23 of the patients. Thus, symptoms possibly caused by histamine in mastocytosis patients are not directly related to urinary histamine metabolite excretion or tissue histamine content.

Human intestinal diamine oxidase: substrate specificity and comparative inhibitor study

For an 80-fold purified preparation of human intestinal diamine oxidase the optimum conditions of incubation, the substrate and the inhibitor specificity were tested. Putrescine was the most favoured substrate but N tau-methylhistamine and 2-methylhistamine were metabolized at optimum conditions with nearly the same velocity. Histamine reached about 50% of the reaction velocity of putrescine. Aminoguanidine and semicarbazide inhibited the human intestinal enzyme like a classical diamine oxidase. However, a distinct inhibition of human intestinal and pea seedling diamine oxidase was observed in presence of beta-aminopropionitrile (weak inhibition of the human enzyme, strong inhibition of pea seedling diamine oxidase) and burimamide (strong inhibition of human intestinal enzyme, nearly no influence on pea seedling diamine oxidase). It is proposed to differentiate on the basis of functional considerations diamine oxidases with more histamine detoxicating activities from those being more involved in regulating polyamine levels in growing tissues.

Metabolism of 14C-histamine given intrabronchially to asthmatic patients

14C-histamine was administered intrabronchially to asthmatic patients and controls. The urinary excretion of total radioactivity, 14C-histamine and its radioactive metabolites was measured. It was found that the excretion of total radioactivity was complete within 24 h. The excretion rate was equal to that observed after intravenous injection of 14C-histamine, indicating a rapid penetration of the bronchial mucosa. However, the diuresis seemed to be of importance for the excretion rate. Histamine inactivation by methylation was more pronounced after intrabronchial than after intravenous administration.

Inhibition of histamine methylation in vivo by the dimaprit analog, SKF Compound 91488

The Dimaprit analog, S-[4-(N,N-dimethylamino)-butyl]isothiurea (SKF Compound 91488), which is a noncompetitive inhibitor (Ki, 0.9 microM) of histamine-N-methyltransferase in vitro, inhibited the methylation of labeled histamine in mice. When administered in combination with the diamine oxidase inhibitor, aminoguanidine, an almost complete block of histamine metabolism was observed. The inhibition was dependent on dose of drug and was apparent with doses of 50 mg/kg and greater. Since Compound 91488 is reported to have no agonist activity of its own, the drug may help to identify the actions of histamine released from endogenous stores in response to physiological and pathological stimuli.

Histamine metabolism in severe obesity before and after jejuno-ileostomy

Histamine metabolism was studied in three patients during histamine-reduced diet before and at intervals after jejuno-ileostomy by analyses of the urinary excretion of non-labelled and 14C-labelled histamine and its metabolites. Labelled histamine was administered intravenously and orally. The preoperative excretion of free histamine and its endogenously formed metabolites was essentially the same as in controls. After intestinal bypass the inactivation of [14C]histamine by both routes of administration was not impaired. Pronounced increases in the excretion of non-labelled conjugated histamine (acetylhistamine) and methylimidazoleacetic acid were found at different intervals postoperatively. This was probably due to histamine synthesis by intestinal bacteria since the diet only contained minute quantities of histamine. It is concluded that the increased urinary excretion of conjugated histamine after intestinal bypass indicated an abnormal bacterial activity in the intestine.

Effects of female sex hormones on histamine metabolism in guinea-pigs

Determination of the urinary excretion of histamine and methylhistamine was performed in intact and gonadectomized male and female guinea-pigs. The excretion of methylhistamine varied more than that of histamine both in the same animal and between different animals. The urinary excretion of histamine and methylhistamine reflects fairly well the total histamine turnover in the animal, provided that aminoguanidine is administered to inhibit diamine oxidase activity. There was no sex difference in the excretion of histamine and methylhistamine and gonadectomy did not influence the urinary output. Female sex steroids had little ifany effect upon histamine turnover in the guinea-pig which is in contrast to the situation in rats and mice.