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[Histamine analogues with nicotine-like action. 11th communication: Structure-activity relationships among histamine analogues (author's transl)].

Structure-activity relationships between histamine and nicrotine are described. If alkyl groups are substituted on the primary amino group of the side chain in histamine the histamine-like action decreases stepwise. While N,N-diethylhistamine (I) clearly shows histamine-like activity, 4-(2-pyrrolidinoethyl)-imidazole (II), an analogue having a pyrrolidine ring in place of the diethylamino group, possesses, on the other hand, distinct nicotine-like properties. The ganglionic stimulation was investigated on the isolated ileum of the guinea-pig, as well as on the blood pressure of the narcotized rat. The nicotine-like effects remained as the imidazole ring was replaced with a pyridine or benzene ring. These results make it plausible to assume that the effect of nicotine-like acting substances is due to an angular conformation, corresponding to nicotine.

Animals↗

Promotion by histamine of carcinogenesis in the forestomach and protection by histamine against carcinogenesis induced by N-nitroso-N-methylnitroguanidine in the glandular stomach in W rats.

The effect of histamine on induction of tumors in the forestomach and the glandular stomach after N-nitroso-N-methylnitroguanidine (MNNG) administration was studied in male inbred W rats. Animals were given 50 micrograms MNNG solution/ml orally for 25 weeks and then 4 mg histamine dihydrochloride sc per day in depot form. Administration of histamine in depot form after MNNG significantly increased the incidence of tumors in the forestomach, but it significantly decreased the incidence of adenocarcinomas in the glandular stomach. All of the tumors induced in the forestomach were of the squamous cell type, and 50% of them were squamous cell carcinomas. Histamine alone had no apparent carcinogenicity in rats.

Adenocarcinoma↗

Histamine release from human leucocytes. A serum factor necessary for the induction of histamine release and desensitization by protein A.

The ability of human leucocytes to release histamine on protein A treatment is lost when the cells are washed repeatedly. It is, however, possible to restore the sensitivity to protein A treatment by incubating the leucocytes in serum. Treatment of the cells with purified IgG does not restore the activity. The material responsible for the resensitization is eluted both in the second and the third protein peak when serum is chromatographed on Sephadex G-200, indicating the possible existence of several active factors. Material with low immunoglobulin content, but with retained capacity to resensitize leucocytes to release histamine on protein A treatment, was obtained by repeated chromatography of peak III material on the Sephadex G-200 column. Furthermore, material from the second and third peaks from Sephadex G-200 deprived of their IgG by passage through a protein A Sepharose or a DEAE-cellulose column had the same capacity to resensitize the leucocytes as unseparated material. When serum was separated by Pevikon block electrophoresis, most of the activity was detected in the alpha and beta regions but only little in the gamma region. The serum fractionations indicate that neither IgG nor the other immunoglobulins are the factor(s) responsible for resensitizing the leucocytes to release histamine on protein A treatment. Beside being necessary for protein A-induced histamine release, the factor (or factors) is also essential for protein A-induced desensitization of human leucocytes.

Bacterial Proteins↗

Imidazole derivatives as a novel class of hybrid compounds with inhibitory histamine N-methyltransferase potencies and histamine hH3 receptor affinities.

In this study, a novel series of imidazole-containing compounds with dual properties, that is, inhibitory potency at the enzyme histamine N(tau)-methyltransferase (HMT) and antagonist potency at histamine H(3) receptors was designed and synthesized. Pharmacologically, these new hybrid drugs were evaluated in functional assays for their inhibitory potencies at rat kidney HMT and for their antagonist activities on synaptosomes of rat cerebral cortex. For selected compounds, binding affinities at recombinant human histamine H(3) receptors were determined. The first compounds (1-10) of the series proved to be H(3) receptor ligands of high potency at rat synaptosomes or of high binding affinity at human H(3) receptors, respectively, but of only moderate activity as inhibitors of rat kidney HMT. In contrast, aminoquinoline- or tetrahydroacridine-containing derivatives 11-17 also displayed HMT inhibitory potency in the nanomolar concentration range. Preliminary data from molecular modeling investigations showed that the imidazole derivative 15 and the HMT inhibitor quinacrine possess identical binding areas. The most interesting compound (14) is simultaneously a highly potent H(3) receptor ligand (K(i)=4.1nM) and a highly potent HMT inhibitor (IC(50)=24nM), which makes this derivative a valuable pharmacological tool for further development.

Aminoquinolines↗

Histamine and histamine receptor antagonists in splanchnic compartments in schistosomal portal hypertension.

The type and distribution of histamine receptors in the portal circulation were studied in patients with schistosomal hypertension. At laparotomy, the umbilical, left gastric, splenic, and superior mesenteric veins were cannulated. Blood samples were drawn from the systemic circulation and from each vein for histamine assay. Portal pressures were then estimated in each vein. One group of patients received local injections of pheniramine p-aminosalicylate (H1-antagonist) in the four cannulated veins simultaneously. A second group received cimetidine (H2-antagonist), and a third group received a mixture of both drugs. Reestimation of portal pressures indicated that all treatments produced a significant drop in pressure in the four compartments. The highest drop was in the splenic vein after the H1-antagonist and in the gastric vein after the H2-antagonist. The histamine level was somewhat higher in the splenic compartment. These results suggest that both H1- and H2-receptors are present in the four portal compartments, but their distribution may not be uniform.

Adult↗

Histamine inhibition of neutrophil lysosomal enzyme release: an H2 histamine receptor response.

Human polymorphonuclear leukocytes treated with cytochalasin B release the lysosomal enzyme beta glucuronidase during contact with serum-activated zymosan particles. Histamine increases intracellular cyclic adenosine monophosphate and inhibits release of this enzyme. The H2 antihistamine metiamide blocks the histamine inhibition of lysosomal enzyme release and the increase in the intracellular adenoisine 3,5'-monophosphate of granulocytes. Chlorpheniramine, an H1 antihistamine, did not block the histamine inhibition of granulocyte lysosomal enzyme release.

Cyclic AMP↗

Chemotactic activity of guinea pig eosinophils for the ECF-A acidic tetrapeptides, histamine, histamine metabolites, and the effect of H1- and H2-receptor antagonists.

Histamine and one of its major metabolites, imidazoleacetic acid, were selectively chemotactic for guinea pig eosinophils, whereas L-histidine, 1,4-methylimidazoleacetic acid, 1,4-methylhistamine and N-acetylhistamine were inactive. The response to histamine was unaffected by concentrations of eosinophils of between 30 and greater than 90% but it was abrogated by preincubation of the cells with histamine prior to assay (self-deactivation). Eosinophilotaxis was also inhibited by H1-(mepyramine-) and H2-)burimamide)-receptor antagonists at high doses (10(-3)m), although at lower concentrations (10(-5) M) inhibition was principally associated with burimamide. The human tetrapeptide, alanine-glycine-serine-glutamic acid, and the analogue, valine-glycine-aspartic acid-glutamic acid, were inactive whereas alanine-glycine-serine-glutamic acid was chemotactic for the guinea pig eosinophil. These results support the concept that the tissue accumulation of eosinophils following anaphylaxis depends on a complex interaction of factors, which in part may be mediated by H2 receptors on the target cells. There may be species differences in the composition of ECF-A.

Alanine↗

Secretion of hyaluronic acid from synovial fibroblasts is enhanced by histamine: a newly observed metabolic effect of histamine.

We obtained evidence for the presence of histamine H1 and H2 receptors in normal synovial fibroblasts. Histamine enhanced proliferation of these synovial fibroblasts and stimulated the release of hyaluronic acid from these tissues. The molecular weight of hyaluronic acid decreased with this stimulation. The release of lower molecular weight hyaluronic acid from the synovium by histamine may be an important factor in joint disease.

Adolescent↗

Modification by histamine H2-receptor blockade of acid secretion stimulated by histamine, pentagastrin and methacholine in the isolated whole mouse stomach.

The direct influences of the blockade of the gastric histamine H2-receptors on the secretory actions induced by histamine, pentagastrin and methacholine, have been studied on the isolated perfused whole mouse stomach. According to the results cimetidine did not modify the spontaneous basal acid secretion. The interactions of cimetidine with the secretagogues were of a competitive nature with histamine and non-competitive with pentagastrin, while no modification of methacholine stimulated acid secretion.

Animals↗

Search for histamine H(3) receptor ligands with combined inhibitory potency at histamine N-methyltransferase: omega-piperidinoalkanamine derivatives.

In an effort to design new hybrid compounds with dual properties, i.e. binding affinity at histamine H(3) receptors and inhibitory potency at the catabolic enzyme histamine N(tau)-methyltransferase (HMT), a novel series of 1-substituted piperidine derivatives was synthesized. This alicyclic heterocycle is structurally linked via aminoalkyl spacers of variable lengths to additional aromatic carbo- or hetero-cycles. These new hybrid drugs were pharmacologically evaluated regarding their binding affinities at recombinant human H(3) receptors, stably expressed in CHO cells, and in a functional assay for their inhibitory potencies at rat kidney HMT. All compounds investigated proved to be H(3) receptor ligands with binding affinities in the micro- to nanomolar concentration range despite significant differences in the type of the aromatic moiety introduced. The most potent compound in this series was the quinoline derivative 20 (K(i) = 5.6 nM). Likewise, all new ligands studied showed impressive HMT inhibitory activities. Here, compounds 5, 10, 14 and 18-20 exhibited submicromolar potencies (IC(50) = 0.061-0.56 microM). The aminomethylated quinoline 19 showed almost the same, well balanced nanomolar activities on both targets. In this study, new hybrid compounds with a dual mode biological action were developed. These pharmacological agents are valuable leads for further development and candidates for treatment of histamine-dependent disorders.

Alkanes↗

Localization of histamine and histamine H2-receptor antagonists in the gastric mucosa.

Histamine stimulates acid secretion by the parietal cell and this secretion is inhibited by the histamine H2-receptor antagonists. Whole body autoradiography showed that radioactivity from 14C-histamine was localized in the artery walls of the stomach and in the muscularis mucosae, but that the level in the fundic mucosa was the same as the blood. When the H2-receptor antagonists burimamide, metiamide and cimetidine were labelled with 35S, 14C or 3H and dosed to rats, whole body autoradiography showed that the stomach was predominantly labelled in the glandular mucosa from 5 to 120 min after administration. Microautoradiography in the rat and dog after intravenous injection of [3H]metiamide or [3H]cimetidine demonstrated an uptake of tritium in the parietal cell cytoplasm that was 3- to 4-times greater than that found in adjacent peptic cells or areas of muscularis mucosa. The preferential labelling persisted at a low level up to 6h after injection in the rat. The localization of radioactivity from the H2-antagonists in the parietal cell cytoplasm correlates well with their pharmacological activity in preventing acid secretion from this cell.

Animals↗

Dose-response relationship of the H1-histamine antagonist, ebastine, against histamine and methacholine-induced bronchoconstriction in patients with asthma.

In a double blind, randomised, placebo controlled trial in a group of extrinsic asthmatics, we have evaluated the potency and selectivity of ebastine, a new piperidine-type H1-receptor antagonist, against histamine and methacholine-induced bronchoconstriction. The median histamine PC20FEV1 value following placebo was 3.15 mg/ml (0.24-58.84). When compared with placebo, ebastine produced significant protection at 10 mg (median PC20 = 31.36 mg/ml, p = 0.008) and 30 mg (median PC20 = 42.14 mg/ml, p = 0.001) but there appeared to be no significant dose effect. Ebastine also produced a small shift in the methacholine concentration-response curves to the right. We conclude that ebastine is an effective antagonist of histamine-induced bronchoconstriction in the asthmatic airway with evidence of minor blockade of methacholine-induced bronchoconstriction.

Adult↗

Evaluation of novel compounds interacting with H2-histamine receptors: effect on histamine-sensitive adenylate cyclase activity in guinea-pig gastric mucosa.

The activity of a number of compounds belonging to the novel class of N-imidazolylphenyl-N'-alkyl-formamidines on histamine-sensitive adenylate cyclase was evaluated. All substances inhibited histamine-dependent adenylate cyclase activation. The compounds which were investigated in a wider concentration range, i.e. DA 4360, DA 4577, and DA 4626, behaved as simple competitive antagonists, yielding apparent KB values comparable with those estimated in conventional H2-receptor assays. These results provide further evidence for the highly selective H2-receptor antagonism of these new molecules, and confirm the suitability of the histamine-stimulated adenylate cyclase assay in guinea-pig gastric cells as a functionally reduced system for the study of H2 antagonists.

Adenylyl Cyclase Inhibitors↗

Characterization of vascular histamine H1-receptors: multiple affinity states of aortic histamine H1-receptor.

We have shown that [3H]mepyramine labels histamine H1-receptor-binding sites in bovine aortic membranes. Further characterization of H1-receptors in this tissue was done by the interaction of an unlabelled histamine receptor agonist or antagonist, with the radioantagonist [3H]mepyramine-binding sites. The competition-binding assays have uncovered differences in the characteristics of the agonist/receptor interaction not shared by antagonists. Agonists interact in the heterogeneous manner with the radioantagonist-labelled sites, showing shallow competition curves with the nH 0.50-0.72, whereas antagonists were devoid of this effect (steeper slopes of the inhibition curves nH approximately 1). The results suggest the presence in this tissue of multiple affinity states of histamine H1-receptor, differentiated by high and low affinity for agonists and the same affinity for antagonists.

Animals↗

The differential reaction of histamine and N tau-methylhistamine with Pauly's diazo reagent: application to assay of histamine N-methyltransferase activity.

A simple nonradioisotopic fluorescent method for assay of histamine N-methyltransferase (HMT) activity was developed. After termination of the HMT reaction, the remaining excess substrate, histamine, was degraded by Pauly 's diazo reagent, whereas the product, N tau-methylhistamine (N- MeHA ), was not degraded by the reagent. Then the mixture was applied to high-performance liquid chromatography under conditions in which N- MeHA was not separated from histamine, and N- MeHA was measured fluorometrically by condensation with o-phthalaldehyde. The method would be convenient for measurement of HMT activity during enzyme purification.

Animals↗

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.

Animals↗

Histamine metabolism. II. Cellular and subcellular localization of the catabolic enzymes, histaminase and histamine methyl transferase, in human leukocytes.

Histaminase (EC 1.4.3.6) activity has been demonstrated in human eosinophils and neutrophils, but not in mononuclear cells, with the use of a new and specific thin-layer radiochromatographic enzyme assay. Leukocyte histaminase was physicochemically and functionally similar to histaminase isolated from human placenta and was principally localized to the 27,000-g granule-rich fraction of eosinophil and neutrophil homogenates. Histamine methyl transferase (EC 2.1.1.8), on the other hand, was detected in monocytes but not in granulocytes, eosinophils, lymphocytes, or platelets, and was localized solely to the 100,000-g cell sap supernatant fraction. These data suggest a role of human leukocytes in the catabolism of histamine and therefore in the modulation of histamine-mediated inflammatory reactions.

Amine Oxidase (Copper-Containing)↗