Evoked Histamine Release Research Articles

Activation of Nociceptive C‐fiber Subtypes in Mouse Skin by Bee Venoms

Bee stings are extremely painful and in allergic subjects a cause of life‐threatening anaphylaxis. We have previously developed a dorsal thoracic skin‐nerve preparation to define sub‐groups of afferent C‐fibers innervating mouse skin. These comprise low mechanical threshold C‐fibers (C‐LTMs) which failed to directly respond to inflammatory mediators, and high mechanical threshold C‐fibers (C‐HTMs). The C‐HTMs could be further subdivided into two subgroups, one responding strongly to pruritogens such as histamine, chloroquine (CQ), BAM8‐22, and mast cells activation; the other failing to respond to these pruritogens, but respond strongly to 5‐HT and ATP (Mol Pharmacol. 2018, 94:1047–1056). Both types of C‐HTMs are activated by capsaicin. Here we evaluated the response of the two subgroups of C‐HTMs to venoms applied directly to the receptive fields in isolate skin. We evaluated the venom of honey bees, wasps and yellow jackets. Venom from each activated both types of C‐HTMs. Based on peak Hz of C‐fiber discharge, the relative strength of activation was: yellow jacket > honey bee ≈ wasp. CQ‐sensitive C‐fibers were activated by venoms to a greater extent than CQ‐insensitive C‐fibers. For example, bee venom evoked 6 ± 2 Hz (n=3) and 2 ± 0.4 Hz (n=7) in CQ‐sensitive vs CQ‐insensitive C‐fibers, respectively. Melittin, an active ingredient in bee venom mimicked the venoms in strongly activating C‐HTMs, with CQ‐sensitive being more strongly stimulated than CQ‐insensitive (9 ± 4 Hz (n=3) vs 1 ± 0.2 Hz (n=3), respectively). We hypothesize that CQsensitive C‐fibers are more strongly activated because unlike the CQ‐insensitive C‐HTMs, they can be stimulated as a consequence of mast cell activation (Neuroscience. 2019; 410:55–58). Indeed, melittin (10 μg/ml) caused mast cell activation (histamine release) in isolated skin fragments (76 ± 19 ng/g, above baseline, n=4); for comparison, compound 48/80 (30 μg/ml) evoked a net 203 ± 46 ng/g of histamine. The degree of melittin‐induced histamine release was not different between wildtype and MrgprB2 knockout mice, whereas compound 48/80 evoked histamine release only from the skin of wildtype mice. The data show that bee venom directly and strongly activates the terminals of virtually all high threshold nociceptive C‐fibers in mouse skin. The prurigentic subtype of C‐fibers are the most strongly activated, and this may be due to the additional indirect effect of mast cell activation, that occurs independently of MrgprB2 receptors.Support or Funding InformationThis work was supported by Department of Education, Slovakia (VEGA 1/0306/18).

The antinociception of oxytocin on colonic hypersensitivity in rats was mediated by inhibition of mast cell degranulation via Ca(2+)-NOS pathway.

This study was conducted to investigate the effects of oxytocin (OT) on visceral hypersensitivity/pain and mast cell degranulation and the underlying mechanisms. We found that oxytocin receptor (OTR) was expressed in colonic mast cells in humans and rats, as well as in human mast cell line-1 (HMC-1), rat basophilic leukemia cell line (RBL-2H3) and mouse mastocytoma cell line (P815). OT decreased 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced visceral hypersensitivity, colonic mast cell degranulation and histamine release after mast cell degranulation in rats. Also, OT attenuated the compound 48/80 (C48/80)-evoked histamine release in P815 cells and inward currents, responsible for the mast cell degranulation, in HMC-1, RBL-2H3 and P815 cells. Moreover, these protective effects of OT against visceral hypersensitivity and mast cell degranulation were eliminated by coadministration of OTR antagonist atosiban or a nonselective inhibitor of nitric oxide synthase (NOS), NG-Methyl-L-arginine acetate salt (L-NMMA). Notably, OT evoked a concentration-dependent increase of intracellular Ca2+ in HMC-1, RBL-2H3 and P815 cells, which was responsible for the activation of neuronal NOS (NOS1) and endothelial NOS (NOS3). Our findings strongly suggest that OT might exert the antinociception on colonic hypersensitivity through inhibition of mast cell degranulation via Ca2+-NOS pathway.

Effects of sympathetic histamine on vasomotor responses of blood vessels in rabbit ear to electrical stimulation

To investigate the effects of histamine receptor antagonists on vasoconstriction induced by electrical stimulation (ES) on posterior auricular nerve, and to explore the pre- and post-synaptic effects of sympathetic histamine on the vasomotor responses of vascular smooth muscle in rabbit ear. ES was applied to posterior auricular nerves of the whole rabbit ear at 10 Hz, 20 Hz and 40 Hz, respectively. Besides, the whole ear was perfused with different histamine receptor antagonists under constant perfusion pressure, and the changes in the flow rate of perfusate were observed. The flow rate of venous outflow was decreased by ES at all the 3 frequencies. The ES-induced vasoconstriction at 20 Hz and 40 Hz could be partly inhibited by H(1) receptor antagonist chlorpheniramine (P < 0.05). After exhaustion of histamine in mast cells by pretreatment with specific mast cell degranulator compound 48/80, chlorpheniramine could still inhibit the ES-induced flow rate reduction. In contrast, H(2) receptor antagonist cimetidine could enhance the 40-Hz ES-induced flow rate reduction (P < 0.05). Moreover, ES-induced vasoconstriction at the 3 frequencies could all be enhanced by H(3) receptor antagonist thioperamide (P < 0.05). Stimulation on the auricular nerve may evoke histamine release from sympathetic nerves rather than from mast cells. Moreover, the functions of sympathetic histamine vary from pre-synaptic modulation to post-synaptic vasoconstriction or vasodilatation, via activation of different histamine receptors.

Sympathetic histamine exerts different pre‐ and post‐synaptic functions according to the frequencies of nerve stimulation in guinea pig vas deferens

Histamine (HA) was found to be present in the sympathetic nerve terminals of guinea pig hearts and vasa deferentia in our previous study; however, little is known about the functions of this neurogenic HA. In this study, we used guinea pig vasa deferentia to investigate the pre- and post-synaptic functions of HA evoked by different frequencies of sympathetic nerve stimulation. We found that sympathetic nerve stimulation could evoke HA release, which was independent to mast cell degranulator compound 48/80 and mast cell stabilizer cromolyn, but was highly sensitive to Na(+) channel blocker tetrodotoxin and chemical sympathectomy with 6-hydroxydopamine. The neurogenically released HA evoked by 12.5 Hz of nerve stimulation activated only pre-synaptic H(3) receptors and mediated pre-synaptic inhibitory effects, while under 25 or 50 Hz stimulation condition, HA simultaneously activated both pre-synaptic H(3) receptors and post-synaptic H(1) receptors. However, the direct contractile responses evoked by sympathetic HA via H(1) receptors were observed at 50 Hz. HA release and HA-mediated contractile responses upon sympathetic nerve stimulation were significantly inhibited by pre-treatment of histidine decarboxylase inhibitor alpha-fluoromethylhistidine. Furthermore, application of exogenous HA could mimic these pre- and post-synaptic effects. Our findings indicate that HA in sympathetic neurons acts as a neurotransmitter and its functions vary from pre-synaptic inhibition, to post-synaptic facilitation, to direct post-synaptic contractile responses according to sympathetic nerve stimulation frequencies.

Histamine in Macaca mulatto monkey cardiac sympathetic nerve system: A morphological and functional assessment

Our previous study demonstrated the co-localization of histamine with norepinephrine (NE) within superior cervical ganglia (SCG), and the release of histamine from sympathetic nerve endings of guinea pig evoked by stimulations. We have now further investigated that whether the histamine can be synthesized, stored and released from the sympathetic nerve systems of Macaca mulatto monkey, and investigated the modulation of the sympathetic endogenous histamine release through histamine H 3 receptor in the monkey cardiac sympathetic nerve system. Double-labeled immunofluorescence technique was applied to investigate co-localization of histamine and NE in SCG of Macaca mulatto monkey. The cardiac sympathetic nerve terminals (synaptosomes) of Macaca mulatto monkey was prepared and depolarized with 50 mmol/L K +. Histamine released from synaptosomes was detected by spectrofluorometer and regulations of histamine release through Ca 2+, Ca 2+-channel blockers, H 3-receptor agonist ( R)-α-methylhistamine and histamine H 3-receptor antagonist, thioperamide were observed. Co-localization of histamine and NE was identified within the same neuron of SCG. Release of histamine was Ca 2+-dependent and inhibited by N-type Ca 2+-channel blocker ω-conotoxin, but not affected by the L-type Ca 2+-channel blocker lacidipine. Compound 48/80, a mast cell releaser, did not affect cardiac synaptosome histamine exocytosis. Cardiac synaptosome histamine release was augmented by the enhanced synthesis of histamine or the inhibition of histamine metabolism. Histamine H 3-receptor activation by ( R)-α- methylhistamine inhibited high K +-evoked histamine release and thioperamide blocked the effects of ( R)-α-methylhistamine. These results firstly showed that histamine co-existed with NE within sympathetic neurons of monkey and the exocytosis of histamine from sympathetic terminals could be regulated by presynaptic histamine H 3 receptors. Sympathetic histamine may act as a neurotransmitter to modulate sympathetic neurotransmission.

Evidence for histamine as a neurotransmitter in the cardiac sympathetic nervous system

The colocalization of histamine (HA) and norepinephrine (NE) immunoreactivities was identified within the superior cervical ganglia neurons of the guinea pig. HA and NE immunoreactivity levels were significantly attenuated after chemical sympathectomy with 6-hydroxydopamine (6-OHDA). Coexistence of NE and HA was also visualized in the cardiac sympathetic axon and varicosities labeled with anterograde tracer biotinylated dextran amine. Depolarization of cardiac sympathetic nerve endings (synaptosomes) with 50 mM potassium stimulated endogenous HA release, which was significantly attenuated by 6-OHDA or a vesicular monoamine transporter 2 (VMAT2) inhibitor reserpine pretreatments. Compound 48/80, a mast cell releaser, did not affect cardiac synaptosome HA exocytosis. Furthermore, K+ -evoked HA release was abolished by the N-type Ca2+ -channel blocker omega-conotoxin but was not affected by the L-type Ca2+ -channel blocker lacidipine. Cardiac synaptosome HA exocytosis was augmented by the enhanced synthesis of HA or the inhibition of HA metabolism. HA H3-receptor activation by (R)-alpha-methylhistamine inhibited high K+ -evoked histamine release. The HA H3 receptor antagonist thioperamide enhanced K+ -evoked HA release and blocked the (R)-alpha-methylhistamine effect. The K+ -evoked endogenous NE release was attenuated by preloading the cardiac synaptosomes with L-histidine or quinacrine. These inhibitory effects were reversed by thioperamide or antagonized by alpha-fluoromethylhistidine. Our findings indicate that high K+ -evoked corelease of NE and HA may be inhibited by endogenous HA via activation of presynaptic HA H3-receptors. The H3-receptor may function as an autoreceptor, rather than a heteroreceptor, in the regulation of sympathetic neurotransmission and HA may be a novel sympathetic neurotransmitter.

The combination of rat mast cell and rabbit aortic smooth muscle is the simple bioassay for the screening of anti-allergic ingredient from methanolic extract of Corydalis tuber.

We have assessed the release of histamine from mast cells by smooth muscle contraction. 0.3 microg/ml compound 48/80 showed no effect on concentration-response relationship of histamine in rabbit aorta. Compound 48/80 induced release of histamine from rat mast cells. When aorta was stimulated by compound 48/80 in the presence of mast cells, contraction was evoked in concentration-dependent manner. This mast cell-dependent contraction was completely blocked by H1 receptor antagonist, 1 microM diphenhydramine. When mast cells was treated with compound 48/80 inhibitor benzalkonium chloride, mast cell-dependent contraction was inhibited, although benzalkonium chloride itself showed no effect on concentration-response relationship of histamine in rabbit aorta. At high concentration of 10 microg/ml, benzalkonium chloride itself evoked histamine release from mast cells and indeed inhibitory effect of 10 microg/ml benzalkonium chloride on mast cell-dependent contraction was lower than that of 3 microg/ml. We have applied this bioassay to search anti-allergic ingredient from a total methanolic extract of Corydalis tuber (Corydalis turtschaninovii BESSER forma yanhusuo Y. H. CHOU et C. C. HSU). Successively, we have isolated five fractions. The fractions I-IV are identified to be corybulbine (1), tetrahydropalmatine (2), corydaline (3) and yuanhunine (4), respectively. Main component of fraction V is the mixture of 3 and canadine (5). Fractions II and V significantly inhibited mast cell-dependent contraction in rabbit aorta as well as inhibited histamine release from rat mast cells. Furthermore, fractions I, III and V inhibited histamine-induced contraction in rabbit aorta at non-competitive manner. From these results, combination of rat mast cells and rabbit aorta is good bioassay to search the anti-allergic ingredient, and we have obtained effective fractions from Corydalis tuber using this assay.

Effects of methyl p-hydroxybenzoate (methyl paraben) on Ca2+ concentration and histamine release in rat peritoneal mast cells.

1 Mechanisms of methyl p-hydroxybenzoate (methyl paraben) action in allergic reactions were investigated by measuring the intracellular Ca(2+) concentration ([Ca(2+)](i)) and histamine release in rat peritoneal mast cells (RPMCs). 2 In the presence or absence of extracellular Ca(2+), methyl paraben (0.1-10 mM) increased [Ca(2+)](i), in a concentration-dependent manner. Under both the conditions, methyl paraben alone did not evoke histamine release. 3 In RPMCs pretreated with a protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate (PMA) 3 and 10 nM), methyl paraben (0.3-3 mM) induced histamine release. However, a high concentration (10 mM) of the agent did not increase the histamine release. 4 U73122 (0.1 and 0.5 micro M), an inhibitor of phospholipase C (PLC), significantly inhibited the methyl paraben-induced histamine release in PMA-pretreated RPMCs. U73343 (0.5 micro M), an inactive analogue of U73122, did not inhibit the histamine release caused by methyl paraben. 5 In Ca(2+)-free solution, PLC inhibitors (U73122 0.1 and 0.5 micro M, D609 1-10 micro M) inhibited the methyl paraben-induced increase in [Ca(2+)](i), whereas U73343 (0.5 micro M) did not. 6 Xestospongin C (2-20 micro M) and 2 aminoethoxydiphenyl borate (30 and 100 micro M), blockers of the inositol 1,4,5-trisphosphate (IP(3)) receptor, inhibited the methyl paraben-induced increase in [Ca(2+)](i) in Ca(2+)-free solution. 7 In conclusion, methyl paraben causes an increase in [Ca(2+)](i), which may be due to release of Ca(2+) from storage sites by IP(3) via activation of PLC in RPMCs. In addition, methyl paraben possibly has some inhibitory effects on histamine release via unknown mechanisms.

Catestatin (CgA 344–364) stimulates rat mast cell release of histamine in a manner comparable to mastoparan and other cationic charged neuropeptides

Catestatin (bovine CgA 344–364) is a cationic peptide, which besides reducing catecholamine secretion from chromaffin cells in vitro also acts a potent vasodilator in the rat in vivo. The alleged histamine releasing effect of catestatin was tested in vitro in rat mast cells. The most active domain of catestatin (bovine CgA 344–358: RSMRLSFRARGYGFR) caused concentration-dependent (0.01–5 μM) release of histamine from peritoneal and pleural mast cells. The potency and efficacy of catestatin was higher than for the wasp venom peptide, mastoparan. Only in the pleural cells was neurotensin (NT) more potent than catestatin, mastoparan and substance P (SP), consistent with a receptor-mediated histamine release by neurotensin. Amongst these cationic peptides, substance P was least effective. The acidic CgA peptide (WE-14, bovine CgA 324–337) neither stimulated nor modulated histamine release by the cationic peptides. The catestatin and neurotensin evoked histamine release were suppressed by pertussis toxin (PTX), suggesting involvement of a G i subunit. Electron micrographs of rat pleural mast cells responding to catestatin revealed a concentration-dependent discharge of granular material. We propose that catestatin activates histamine release from rat mast cells by a mechanism analogous to that already established for mastoparan and other amphiphilic cationic neuropeptides (the peptidergic pathway) and distinct from the mechanism of inhibition of catecholamine release from chromaffin cells.

The CCK-2 Receptor is Located on the ECL Cell, But Not on the Parietal Cell

Background: The interrelationship between histamine and gastrin in the physiological regulation of gastric acid secretion is still a matter of dispute. CCK-2 receptors are located on enterochromaffin-like (ECL) cells in corpus mucosa and gastrin stimulates acid production by releasing histamine from the ECL cells, which in turn stimulates the parietal cells. Whether parietal cells also possess gastrin receptors of physiological significance is unclear. The aim of the present study was to localize the CCK-2 receptor cellularly and concomitantly demonstrate a gastrin receptor response (histamine release). Methods: Fluorescein labelled cholecystokinin-8 (Fluo-CCK-8) was added to the arterial infusion to totally isolated, vascularly perfused rat stomachs to a final concentration of 130 pmol L -1 for 1 min, either alone or along with 520 nmol -1 CCK-8 after 10-min pre-perfusion with CCK-8. Immediately after the FluoCCK-8 had reached the oxyntic mucosa, biopsies were taken and the binding sites were localized by double immunohistochemistry combined with the tyramide signal amplification (TSA) technique. Venous histamine was measured before and during stimulation. Results: Fluo-CCK-8 (130 pM) evoked histamine release, and binding sites were found in the basal part of corpus mucosa, co-localized with histidine decarbocylase (HDC) immunoreactive ECL cells. No binding of Fluo-CCK was found in the midglandular region of corpus, dominated by parietal cells. Binding of Fluo-CCK-8 was abolished by concomitant perfusion with excess CCK-8. Conclusion: Fluo-CCK-8 given to isolated rat stomachs in a physiological concentration binds to CCK-2 receptors on ECL cells and causes histamine release, whereas no binding of Fluo-CCK-8 to parietal cells was found.

Muscarinic control of histamine release from airways. Inhibitory M1-receptors in human bronchi but absence in rat trachea.

Isolated human bronchi and rat tracheae were incubated in organ baths to measure histamine release. The calcium ionophore A23187, 3 micromol/L in rat trachea and 10 micromol/L in human bronchi, stimulated histamine release by 145 +/- 50% (n = 6) and 270 +/- 48% (n = 7) above the prestimulation level, respectively. Acetylcholine (100 pmol/L; human bronchi) or oxotremorine (1, 100, 10,000 nmol/L; rat trachea) did not affect the spontaneous histamine release. In rat tracheae neither acetylcholine nor oxotremorine inhibited A23187-evoked histamine release, whereas 100 pmol/L acetylcholine significantly suppressed the evoked histamine release in human bronchi by 86%. For receptor characterization the following subtype-specific muscarinic receptor antagonists were applied: pirenzepine (M1 subtype), para-fluorohexahydrosiladifendiol (pFHHSiD; similar affinities at human cloned M1-, M3-, and M4-receptors), AF-DX 116 (M2 subtype), and clozapine (antagonist at cloned M1-, M2-, M3-receptors; agonist at cloned M4-receptors). Pirenzepine, pFHHSiD, AF-DX 116, and clozapine (100 nmol/L each) antagonized the inhibitory effect of 100 pmol/L acetylcholine by 83 +/- 20% (n = 6), 83 +/- 9% (n = 8), 50 +/- 14% (n = 6), and 35 +/- 7% (6). In conclusion, a species difference exists in the cholinergic control of histamine release between human and rat airways. In human airways muscarinic receptors most likely of the M1 subtype are involved in the inhibitory control of mast cell function, whereas such an inhibitory pathway does not exist in the rat trachea.

Not all chronic urticaria is "idiopathic"!

The aetiology of chronic urticaria in the majority of patients is elusive. The cause of physical urticarias (dermographism, delayed pressure urticaria, cold urticaria) is unknown. We have identified a subset of chronic "idiopathic" urticaria patients, representing approximately 30% of the total in which the disease is caused by the presence of IgG autoantibodies against the high affinity IgE receptor (FcepsilonRIalpha). This functional autoantibody stimulates normal (albeit vicarious) activation of mast cells and basophils via FcepsilonRI, causing whealing and angioedema. Anti-FcepsilonRI-positive patients are recognized by a combination of autologous serum skin testing and evoked histamine release from basophils of normal human donors. Autoantibody-positive and -negative patients are clinically indistinguishable and are treated routinely by combinations of H1 and occasionally H2-antihistamines in both cases. However, severely affected patients who are anti-FcepsilonRI-positive can also be treated by non-specific immunotherapy (plasma pheresis, intravenous immunoglobulin, cyclosporin.

Acetylcholine via muscarinic receptors inhibits histamine release from human isolated bronchi.

Human bronchi were incubated in organ baths to measure histamine release. The calcium ionophore A23187 (10 mumol/L; 1 min) stimulated histamine release by 148 +/- 28% (n = 11) above the prestimulation level but was ineffective in epithelium-denuded bronchi. Neither bradykinin (0.1 mumol/L) nor compound 48/80 (10 micrograms/ml) triggered the release of histamine from epithelium-intact bronchi. Acetylcholine did not affect spontaneous histamine release (about 2 nmol/g x 5 min) but inhibited A23187-evoked histamine release in an atropine-sensitive manner. Already a concentration as low as 0.1 nmol/L acetylcholine was effective, the maximal inhibition (by 89%) occurred at 100 nmol/L, whereas a concentration of 10 mumol/L acetylcholine was ineffective. Oxotremorine (1 nmol/L), a stable agonist at muscarinic receptors, suppressed stimulated histamine release completely. Physostigmine (0.1 mumol/L), an acetylcholinesterase inhibitor, reduced A23187-evoked histamine release by 58%. Antihuman IgE antibody stimulated histamine release by 127 +/- 30% (n = 6) above the prestimulation level. Acetylcholine (100 nmol/L) inhibited also the immunologically evoked histamine release by 70%. In conclusion, the present experiments provide a model to characterize mast cells that are localized in or close to the airway surface epithelium. Acetylcholine via muscarinic receptors strongly inhibits the releasability of these mucosal mast cells being among the first cells to interact with inhaled antigens and environmental agents. The inhibitory action of physostigmine indicates the involvement of endogenous, probably non-neuronal acetylcholine expressed in airway epithelial cells.

Effect of cisplatin and cis-platinum (II) phosphonate complex on murine mast cells

We investigated the effect of two cis-platinum (II) complexes, cis-[PtCl 2(NH 3) 2] (cisplatin) and cis-[PtCl 2(4-pmpe) 2] (4-pmpe stands for diethyl 4-pyridylmethylphosphonate), which was recently synthetized in our laboratory, on murine mast cells. We noticed that both tested compounds were able to evoke histamine release from murine mast cells. The histamine secretion was dependent on the concentration of compound and on the time and temperature of the reaction. It was also dependent on metabolic energy (the reaction was diminished in a medium without glucose and abolished in the presence of 2-deoxyglucose). The results indicate that cis-platinum (II) complexes activate mast cells to secrete histamine via a non-cytotoxic, active secretory process.

Exogenous but not endogenous substance P releases histamine from isolated human skin fragments

Neuropeptides such as substance P are released from nerve terminals following the stimulation of sensory fibers, and are thought to participate in neurogenic inflammation in the skin; it is often speculated that mast cell activation is an intermediate step in this process. In the present study we addressed this hypothesis using freshly obtained skin explants derived from human neonatal foreskins or adult skin resections. The results demonstrate that when substance P is released from human skin by incubation in the presence of capsaicin (10 −5 M), no histamine is released from human isolated skin fragments. In each experiment human recombinant stem cell factor and/or exogenously applied substance P effectively evoked histamine release from the explants, attesting to the viability of the mast cells in the preparation. The concentrations of exogenously applied substance P required to elicit histamine release, however, were large (> 10 μM). These results indicate that substance P released from cutaneous sensory nerve fibers does not reach sufficient concentrations in the skin to degranulate mast cells. These data support the hypothesis that the vascular effects of neurogenic inflammation occur independently of mast cell activation.

Selective potentiation of IgE-dependent histamine release from rat peritoneal mast cells by stem cell factor

Effect of stem cell factor on histamine release from rat peritoneal mast cells was studied. Although stem cell factor did not evoke histamine release by itself, it clearly potentiated histamine release from sensitized mast cells caused by antigen, anti-IgE and concanavalin A. However, stem cell factor did not affect histamine release caused by compound 48/80, calcium ionophore A23187 and substance P. Although maximum potentiation of antigen-induced histamine release by stem cell factor was accomplished after 1–10 minute-preincubation, potentiation was declined after a longer incubation period. Potentiation of histamine release by phosphatidylserine and non-mast cells in the rat peritoneal cavity was incubation time-dependent. Potentiation by stem cell factor was additive to that by phosphatidylserine or non-mast cells. These results indicate that stem cell factor selectively potentiates IgE-dependent histamine release from rat peritoneal mast cells, and suggest that the mechanism involved is distinct from that of phosphatidylserine or non-mast cells in the rat peritoneal cavity.

Choice of muscle relaxants in patients with heart disease

Summary The presence or absence of circulatory effects induced by muscle relaxants is often cited in the decision process for selection for the most appropriate drug for production of skeletal muscle paralysis in patients with heart disease undergoing surgery. With the exception of pancuronium, all the other currently available nondepolarizing muscle relaxants are devoid of circulatory effects or evoke histamine release only when large doses (about 3×ED95) are administered rapidly. Indeed, it seems undeniable that the circulatory effects of muscle relaxants, when they do occur, are modest, transient, and rarely of clinical significance. More important than muscle-relaxant-induced circulatory effects is their recovery profile and the likelihood that residual (“subclinical”) skeletal muscle paralysis will persist despite drugassisted antagonism. In this regard, when the issue of patient safety is considered, the higher cost of short-acting and intermediate-acting nondepolarizing muscle relaxants seems justifiable. What a difference 10 years can make!29

Neuropeptide Y and truncated neuropeptide Y analogs evoke histamine release from rat peritoneal mast cells. A direct effect on G proteins?

Several regulatory peptides, including neuropeptide Y, can release histamine from mast cells. In the present study we investigated which parts of the neuropeptide Y molecule are required to evoke the release of histamine from isolated rat peritoneal mast cells. In addition, we examined whether the histamine release evoked by neuropeptide Y (and by compound 48 80 ) is sensitive to the G protein inhibitors pertussis toxinand benzalkonium chloride. Neuropeptide Y released histamine in a concentration-dependent manner. Also a neuropeptide Y analog with the center part substituted by 8-aminooctanoic acid, [Aoc 2–27]neuropeptide Y, and the cyclic form of the C-terminal hexapeptide, cyclic neuropeptide Y-(31–36), released histamine. The three peptides were equally effective and equally potent. Neuropeptide Y-(1–24)NH 2 also released histamine, but its efficacy was low. The rank order of potency of the analogs tested did not agree with that of any of the previously known or postulated neuropeptide Y receptors. Pretreatment of mast cells with pertussis toxin or benzalkonium chloride markedly inhibited the histamine release evoked by neuropeptide Y, [Aoc 2–27]neuropeptide Y and compound 48 80 . In conclusion, most of the histamine-releasing activity of neuropeptide Y resides in the six C-terminal amino acid residues. The release appears to be G protein-dependent and is probably not receptor mediated.

Characterization of the prostaglandin E receptor expressed on a cultured mast cell line, BNu-2c13

Interleukin 3-dependent BNu-2c13 mast cells, mucosal type-like mast cells, exhibited a specific high-affinity binding site for [ 3H]prostaglandin (PG) E 2. The binding was completely displaced by M&B 28767, an EP 3-selective agonist, but not by EP 1- or EP 2-selective ligands, indicating that the PGE 2 binding site is of the EP 3 subtype PGE receptor. Whereas the EP 3 subtype is presumed to be coupled to inhibition of adenylate cyclase in various tissues and cells, in BNu-2c13 cells PGE 2 had no ability to inhibit adenylate cyclase activity, while it induced concentration-dependent stimulation of phosphoinositide metabolism and caused an increase in the intracellular free Ca 2+ concentration in a pertussis toxin-sensitive manner. PGE 2 by itself did not evoke histamine release from the cells, but it markedly stimulated histamine release in concert with ionomycin, a Ca 2+ ionophore. The PGE 2-stimulated release was also comletely blocked by pertussis toxin. Thus, the PGE receptor expressed on BNu-2c13 mast cells is of the EP 3 subtype and is linked to phosphoinositide metabolism via a pertussis toxin-sensitive G protein, and this activation leads to histamine release.

Non-immunological release of histamine from rat mast cells elicited by antineoplastic agents.

We studied the histamine-releasing activity of several antineoplastic drugs on rat pleural and peritoneal mast cells. The drugs tested included the nitrogen mustards cyclophosphamide and ifosfamide, the nitrosourea carmustine, the triazene dacarbazine, the folic acid analogue methotrexate, the pyrimidine analogue cytarabine and fluorouracil, the vinca alkaloids vinblastine, vincristine and Vinorelbine, the epipodophyllotoxins etoposide and teniposide, and the enzyme L-asparaginase. Methotrexate, carmustine, fluorouracil, vinblastine and vincristine failed to elicit histamine release on rat mast cells. All of the other drugs evoked histamine release in both the presence and the absence of extracellular calcium, but ifosfamide, cytarabine and asparaginase induced a much lower release in the absence of this cation. The response elicited by cytarabine and etoposide was much higher in pleural than in peritoneal mast cells. These results indicate that some antineoplastic drugs may directly activate the release of histamine, which could contribute to some of their secondary effects.