Inhibitory effect of phloretin on histamine release from isolated rat mast cells

The ability of the flavonoid phloretin to inhibit histamine release from rat mast cells varied considerably with the releasing agent investigated. The response to the combination of the ionophore A23187 and the phorbol ester TPA and to suboptimal concentrations of the ionophore (0.5 microM) was potently inhibited (IC50 about 5 microM), whereas phloretin was less potent against responses to the ionophore (1 microM) (IC50 of 17 microM), to antigen alone and in combination with TPA (IC50 of 30-50 microM), to TPA in the absence of calcium (IC50 of 50 microM) and to compound 48/80 in the absence and presence of calcium (IC50 of 60-90 microM). The inhibition by phloretin at concentrations above 10 microM was partly counteracted by glucose (5 mM) indicating effects on oxidative metabolism. The flavonoid quercetin was equally potent in inhibiting histamine release induced by antigen, the ionophore at different concentrations and in combination with TPA (IC50 of 20 microM). Although not conclusive, the results are consistent with an inhibition of protein kinase C by phloretin at concentrations below 10 microM. At higher concentrations unspecific actions become apparent and phloretin therefore seems to be of limited utility as a probe for signal-pathways in cell responses.     

The effect of glycoprotein from Candida albicans on isolated rat mast cells

Glycoprotein, a polymeric compound from Candida albicans, releases histamine from isolated rat mast cells. This was shown to be due to degranulation, as observed by light microscopy.     

Inhibitory effect of lysophosphatidylcholine on the histamine release from rat peritoneal mast cells

Histamine release from isolated rat peritoneal mast cells induced by compound 48/80 (0.5 microgram/ml) or antigen-antibody reaction was inhibited by lysophosphatidylcholine in a dose-dependent fashion at concentrations up to 4 microM. Within the same range of concentration, lysophosphatidylcholine exhibited a membrane-stabilizing action on the model membrane systems decreasing the permeability of lipid bilayer and the fluidity of liposomal membrane in the liquid crystalline state. At concentrations higher than 8 microM, lysophosphatidylcholine damaged the cell membrane and subsequently histamine was released. It was assumed that lysophosphatidylcholine may act as an endogenous membrane stabilizer inhibiting histamine release in normal mast cells.     

The effect of platelet-activating factor on histamine release from rat peritoneal mast cells.

The effect of platelet-activating factor (PAF) on histamine release from peritoneal mast cells of adult and young male rats was investigated. PAF alone tended to release histamine from the mast cells of adult and young rats, although very slightly. On the other hand, PAF significantly inhibited the histamine release induced by the Ca2+ ionophore A23187 in mast cells obtained from rats of either age group, but not that by compound 48/80. Such inhibition was not seen with lyso-PAF. CV-3988, a PAF antagonist, antagonized the inhibitory effect of PAF on the A23187-induced histamine release in mast cells from adult and young rats. These results suggest that PAF does not have a strong histamine-liberating action on mast cells, and that PAF inhibits the calcium influx into mast cells through the activation of PAF receptors.     

The effect of adrenocorticotropin on histamine and 5-hydroxytryptamine secretion from rat mast cells

Characteristics of histamine (Hi) and 5-hydroxytryptamine (5-HT) release from rat peritoneal mast cells in response to the polypeptide adrenocorticotropin (ACTH) were studied. During a 15 min incubation at 37 degrees C, ACTH evoked Hi as well as 5-HT release from rat mast cells at concentrations of 1 X 10(-4) M-1 X 10(-3) M. The release was dose-dependent and very rapid. After 15 sec the amount of the amines released was the same as after 4.5 min. In most experiments, the percentage of Hi release was slightly but significantly higher than the percentage of 5-HT release. Hi and 5-HT release induced by ACTH also took place in a calcium-free medium. However, the release of the amines was decreased when calcium was omitted. Comparison of the effects of ACTH, compound 48/80 and substance P on mast cell secretion showed that ACTH is about 100 times less active then substance P which was in turn about 100 times less active than compound 48/80. When both ACTH and compound 48/80 were used together as liberators , the release was significantly higher than with either liberator alone. Our results indicate that there are receptor sites for the endogenous polypeptide ACTH on the mast cell membrane which mediate Hi and 5-HT release. This release was found to resemble that evoked by the basic secretogogue compound 48/80 but in some aspects to be different from that evoked by substance P.     

Anthracycline-induced histamine release from rat mast cells

Comparisons were made of the ability of doxorubicin, daunorubicin, rubidazone and aclacinomycin A to release histamine from rat peritoneal mast cells. Preliminary in vitro experiments indicated that doxorubicin (10(-6) to 2.5 X 10(-4) M), in contrast to compound 48/80 and the calcium ionophore A23187, did not produce significant release under any condition tested when purified or unpurified rat mast cells were used. In in vitro experiments, released histamine was measured in the cell-free supernatant of peritoneal fluid of rats after intraperitoneal injection of the agents. The time course of doxorubicin-induced histamine release from the peritoneum was rapid, with maximal release occurring within 4 to 6 min. Dose-response curves of the 4 agents over the range 10(-5) to 3.3 X 10(-3) M revealed that all caused histamine release, with 10(-3) M concentrations of each causing maximal release of comparable magnitude to that produced by 9.5 X 10(-6) M A23187. Treated mast cells recovered from the peritoneal cavity showed degranulation and vacuolization when examined by electron microscopy. Increased vascular permeability by the Evans-blue test was also noted with all 4 agents, and zones were of comparable size after injection of the highest concentration of each agent. The results indicate that in vivo, doxorubicin, daunorubicin, rubidazone and aclacinomycin A cause a rapid release of histamine from rat mast cells and an increase in vascular permeability in rat sin. There also appeared to be a reasonable correlation between the blueing reaction and histamine release in the peritoneal cavity in that the doses that did not cause skin blueing also failed to cause histamine release. The lack of histamine release by doxorubicin from mast cell preparations in vitro suggests that alterations to the doxorubicin molecule or the presence of other critical substances may be necessary for this activity to commence.     

Effects of benzodiazepines on serotonin release from rat mast cells

Ro5-4864, diazepam and chlordiazepoxide inhibited the concanavalin A-induced [14C]serotonin release from rat mast cells dose dependently with IC30 values 38, 115 and 160 microM, respectively. They also inhibited concanavalin A-induced 45Ca uptake, with IC50 values 180, 860 and 1800 microM, respectively. Clonazepam slightly inhibited serotonin release, but medazepam did not, and neither compound inhibited the calcium uptake stimulated by concanavalin A. The potencies of benzodiazepines to inhibit concanavalin A-induced serotonin release and 45Ca uptake were correlated with their binding affinities to the peripheral type of benzodiazepine binding sites. At higher concentrations, these benzodiazepines caused release of both serotonin and lactate dehydrogenase, due to their cytotoxicity. The calcium channels of mast cells are probably not voltage-dependent, as the agonists of voltage-dependent calcium channels, Bay k 8644 and YC-170, did not stimulate serotonin release. Moreover, Ro5-4864, diazepam and chlordiazepoxide inhibited A23187-induced serotonin release. Mast cells have high contents of calmodulin (602 +/- 20 ng/10(6) cells), and benzodiazepines inhibited calmodulin. The benzodiazepine inhibitory effects on the serotonin release induced by A23187 seemed to be partly due to their calmodulin-inhibiting activities. These results suggest that inhibition of serotonin release by benzodiazepines in mast cells activated by concanavalin A is mainly due to inhibition of calcium channels, which may be controlled by the peripheral type of benzodiazepine binding sites.     

Effect of methylmercury on histamine release from rat mast cells

Methylmercury chloride (MeHgCl) is well known as a significant environmental hazard, particularly as a modulator of the immune system. As it is acknowledged that the critical effector cells in the host response participating in various biological responses are mast cells, we tried to define the possible contribution of mast cells in the development of methylmercury-evoked effects. We investigated the effects of methylmercury on the rat mast cell degranulation induced by non-immunological stimuli (the selective liberator of histamine, compound 48/80, and calcium ionophore A23187) both in vivo and in vitro. Using the cells prepared from methylmercury-intoxicated rats through a 5-day treatment of MeHgCl (10 mg/kg/day), we observed the suppression of calcium ionophore A23187- and 48/80-induced histamine release, which was enhanced with time after treatment. Similar suppression was observed in the ionophore-stimulated release, when cells were prepared from rat with a single treatment of MeHgCl (20 mg/kg). It should be noted that when cells from the control rat were pre-incubated with methylmercury in vitro at a 10(-8) M concentration for 10 min, A23187 and compound 48/80-stimulated histamine release was significantly enhanced. However, when the pre-incubation period was prolonged to 30 min, the release was suppressed. An increase in the methylmercury concentration to 10(-6) M also suppressed the histamine release. These results show that methylmercury treatment can modify mast cell function depending on concentration and time, and might provide an insight into the role of mast cells in the development of methylmercury-stimulated effects.     

Dependence of histamine release from rat mast cells on adenosine triphosphate

Summary using pure populations of rat mast cells, the relation of the ATP content of the cells to histamine release induced by compound 48/80 has been studied. Variable ATP levels in the mast cells have been produced by incubation with appropriate concentrations of oligomycin.The dose-response curves of oligomycin for the inhibition of histamine release and for the reduction in the ATP content of the mast cells are similar. The concentration required for 50% inhibition of histamine release is, however, higher than that for 50% reduction of the ATP level.Comparative study of the reduction of the ATP content and the inhibition of histamine release in samples of the same suspension of mast cells shows a linear relation between 10 to 90% inhibition of histamine release and 40 to 95% inhibition of ATP synthesis.The observations support the hypothesis that ATP is involved in the process of histamine release from mast cells induced by compound 48/80.     

Effects of beta-endorphin on rat mast cells

The endogenous opioid peptide beta-endorphin induced a dose-dependent release of histamine from rat peritoneal mast cells. The threshold concentration was around 10(-6) M and the optimal concentration of 2 X 10(-5) M released 35% of the total histamine. The release of histamine was very rapid, complete within 10 s, and very similar to that induced by neurotensin or compound 40/80. The histamine release was temperature dependent and inhibited at increased extracellular calcium concentrations. Taken together, the findings indicate that the release of histamine induced by beta-endorphin is a specific, energy-dependent process. The pattern of release has much in common with that induced by other basic peptides, such as neurotensin, dynorphin and substance P.     

Studies on histamine-retaining granules obtained from isolated rat mast cells.

Histamine-retaining granules were isolated from rat mast cells after sonication in either sucrose of Ficoll-Hypaque media. The preparations obtained were compared in regard to recovery and spontaneous loss of histamine. The effect of agents known to release histamine from intact rat mast cells (antigen, compound 48/80, decylamine, the ionophores A23187 and X537A as well as ATP) was studied on the granules. Antigen and compound 48/80 did not release histamine. Decylamine and X537A induced a pronounced release independent of the presence of divalent cations. ATP caused a small, but significant release, which showed an absolute requirement for magnesium. A23187 released histamine only in the presence of either calcium or magnesium, and this release was unaffected by certain agents known to inhibit histamine release from intact rat mast cells. The results seem to exclude the possibility that agents known to induce release of histamine from intact rat mast cells by a calcium-and energy-dependent process would exert this action through a direct effect on intracellularly localized granules.     

Peptides and histamine release from rat peritoneal mast cells

Various vasoactive peptides were compared for their histamine releasing effects on rat mast cells. Neurotensin, substance P (SP), and kallidin were the most active natural peptides, followed by bradykinin; neurokinin A and B, bombesin, angiotensin and tuftsin were practically inactive. Several kinins and tachykinin-related peptides were tested in an attempt to characterize the receptors mediating histamine liberation. The order of potency of the kinins was the following: kallidin greater than [Tyr(Me)8]bradykinin = bradykinin greater than [desArg10]kallidin greater than desArg9-bradykinin, the same as that found in smooth muscle possessing receptors of the B2 type. Tachykinin-related peptides were potent stimulants and followed the order: [D-Tryp7,9,10]SP-(1-11) greater than [D-Pro2,D-Tryp7,9,10]SP-(1-11) greater than SP-(1-11) greater than SP-(1-9) greater than [D-Pro4,D-Tryp7,9,Leu11]SP-(4-11) greater than SP-(1-7) greater than SP-(4-11) greater than neurokinin A = neurokinin B, indicating that: (a) undecapeptide antagonists of SP behave as superagonists; (b) both N- and C-terminal portions of SP-(1-11) are essential for activity; and (c) receptors for the tachykinins mediating histamine release appear to be of the SP-P type.     

Histamine release from saponin-permeabilized rat mast cells by calcium

The first effect of receptor activation on the mast cell surface, initiating histamine secretion, is an increase in the cytosol Ca2+ concentration. It should then be possible to induce histamine secretion by calcium alone, if the calcium permeability of the cell membrane could be increased without any significant interference with the physiological cell functions. This was achieved in the present study by adding low concentrations of saponin (0.0005% and 0.001% w/v) to the medium. When calcium was added to the saponin-permeabilized cells, around 40% histamine release occurred with 0.25 mM extracellular calcium (free Ca2+ 0.15 mM). The release was inhibited by antimycin A (1 microM). Transmission electron microscopy showed formation of vacuoles containing granules stripped of their membranes, which characterize a secretory response. The observations are consistent with a limited increase in the calcium permeability of the cell membrane for a brief period. There was apparently an increase in the cytoplasmic calcium concentration, which acted through calmodulin, since the histamine release induced by calcium from the permeabilized mast cells could be inhibited by a calmodulin-antagonist, mepacrine (10-30 microM).     

黄药子醇提物抑制胃癌细胞功能的研究

目的研究黄药子醇提物对人胃癌细胞增殖、克隆形成和迁移能力的影响。方法制备黄药子醇提物,根据细胞培养液所含黄药子醇提物的不同浓度,将实验分为黄药子醇提物高浓度组(120 mg/L)、低浓度组(60 mg/L)和对照组(等量无菌水)。通过体外MTT、克隆形成实验、细胞迁移实验,分别检测黄药子醇提物对人胃癌细胞系MGC803增殖、克隆形成和迁移能力的影响。结果与对照组相比,黄药子醇提物高浓度组和低浓度组胃癌细胞体外增殖速度明显减慢(培养第2~6天时,F分别为29.130、21.864、67.826、36.015、43.656,均P<0.01)、平板克隆形成率明显减少(F=11.918,P<0.01),黄药子醇提物高浓度组的细胞迁移能力明显降低(F=4.258,P<0.05)。结论黄药子醇提物可以显著抑制胃癌细胞增殖、克隆形成和迁移能力,具有潜在的抑制胃癌细胞转移的能力。     

Estimation of the rate of energy production of rat mast cells in vitro

Rat mast cells were treated with glycolytic and respiratory inhibitors. The rate of adenosine triphosphate depletion of cells incubated with both types of inhibitors and the rate of lactate produced in presence of antimycin A and glucose were used to estimate the rate of oxidative and glycolytic ATP synthesis.     

Effect of dantrolene on histamine release from rat peritoneal mast cells.

Dantrolene strongly and dose-dependently inhibited histamine release from rat peritoneal mast cells induced by anti-IgE. Dantrolene inhibited Ca(2+)-mobilization from intracellular Ca(2+)-store as well as histamine release in mast cells activated by anti-IgE, the effect on both these phenomena being closely correlated. These results suggested that the effect of dantrolene on histamine release from rat mast cell might be due to the inhibition of Ca(2+)-release from intracellular Ca(2+)-store.     

Effect of cromoglycate on anaphylactic histamine release from rat peritoneal mast cells

Cromoglycate (1-30 muM) produced a concentration-dependent inhibition of anaphylactic histamine release from actively sensitized rat peritoneal mast cells but at lower concentrations (0.01-0.1 muM) occasionally produced a concentration-dependent enhancement of histamine release.     

Dual effect of magnesium on compound 48/80-induced histamine secretion from rat peritoneal mast cells.

The effect of magnesium on the secretory response to compound 48/80 from rat peritoneal mast cells was studied. The decrease in secretion caused by calcium deprivation was enlarged by magnesium. Glucose partially counteracted the decrease caused by calcium deprivation but not the one caused by magnesium. The addition of calcium to the cells simultaneously with compound 48/80 completely restored the secretory response if magnesium was present. The response was only partially restored in a magnesium- and glucose-free medium, whereas it was almost completely restored if glucose was present. Magnesium had a considerable effect on the restoration of the secretory response of EGTA-treated cells, whereas the effect of glucose was minimal indicating that an effect on the energy metabolism was of minor importance. The secretory response could also be restored by an exposure of the cells to calcium prior to stimulation with compound 48/80. This was, however, only observed if magnesium was present and glucose had no effect. The influence of magnesium on the restoration of the secretory response may partly occur by an effect on the energy metabolism, partly by an effect on the stimulus-secretion coupling. We propose that insufficient supply of Mg2+ to the G-protein during activation by compound 48/80 might cause a suboptimal signal transduction.     

Properties of hydrogen peroxide-induced histamine release from rat mast cells

Incubation of rat peritoneal mast cells with hydrogen peroxide results in a marked release of histamine. Maximal release is observed with 0.05–0.1 mM H₂O₂, but higher concentrations of H₂O₂ instead suppresses the release. Histamine release starts after about 2 min of lag time and reaches a plateau in about 10 min. Hydrogen peroxide-induced release does not exceed 50–60 per cent of total histamine if the incubations are prolonged or additional H₂O₂ is given at 10 min. This would be explained by the fact that H₂O₂ causes impairment of the histamine releasing system of mast cells simultaneously with the release of histamine. Hydrogen peroxide-induced release is not due to nonspecific lysis of the cells because lactate dehydrogenase, a cytoplasmic enzyme, is not liberated during the reaction. The reaction requires the presence of Ca²⁺, is enhanced by D₂O and suppressed by colchicine. It is not, however, affected by dibutyryl cAMP or dibutyryl cGMP. No significant alteration of intracellular levels of cyclic AMP and cyclic GMP is observed during the incubation of mast cells with 0.1 mM H₂O₂. These results indicate that microtubular functions would be involved in the releasing reaction although they are not under the control of cyclic nucleotides. Microscopic observation shows that H₂O₂-induced release is accompanied by degranulation.