Neurotensin stimulates histamine release from the isolated, spontaneously beating heart of rats

Neurotensin (NT) evoked a transient, dose-dependent histamine release (ED50 170 ng ml-1) from the rat perfused heart. Histamine release by NT occurred within seconds and lasted less than 2 min. The histamine releasing effect of NT was followed by a dose-dependent increase of the perfusion pressure and a slight tachycardia. The histamine releasing effect of NT was completely abolished in hearts derived from rats pretreated for 3 days with high doses of compound 48/80. The coronary vasoconstrictor effect of NT was increased in hearts derived from compound 48/80-pretreated rats. The mast cell inhibitor cromoglycate markedly inhibited NT-induced histamine release without affecting the coronary vasoconstrictor effect of NT. The histamine releasing effect of NT was inhibited, while its coronary vasoconstrictor effect was markedly potentiated, in hearts derived from rats pretreated with the antiallergic and antiinflammatory steroid dexamethasone. The increase of perfusion pressure evoked by NT was not modified by antihistamine drugs. Infusions of exogenous histamine (10(-6)-10(-5) g ml-1) caused a dose-dependent coronary vasodilation in the rat perfused heart. The results suggest that NT stimulates histamine release from cardiac mast cells. These results together with those obtained in previous studies suggest that mast cell mediators (particularly histamine and serotonin) are unlikely to be responsible for the coronary vasoconstrictor effect of NT in the rat perfused heart.     

Characterization of the histamine releasing effect of neurotensin in the rat heart

Bolus injections of neurotensin (NT) in the rat perfused heart elicited a transient, dose-dependent histamine release. The histamine releasing effect of NT appears to be independent of the heart rate and coronary perfusion pressure and it was not influenced by atropine, propanolol, prazosin, methysergide, ketanserin, indomethacin, morphine, lidocaine or by removal of the atria. However, it was potentiated by adenosine, inhibited by sub-stimulatory concentrations of NT and the mast cell membrane stabilizing drug cromoglycate but was unaltered by the calcium antagonist verapamil. The absence of calcium in the heart perfusate suppressed the histamine releasing effect of NT. These results suggest that the histamine releasing effect of NT in the rat heart results from a direct effect on ventricular mast cells and is calcium-dependent.     

Involvement of mast cells in basal and neurotensin-induced intestinal absorption of taurocholate in rats

Neurotensin (NT), a hormone released from intestine by ingested fat, facilitates lipid digestion by stimulating pancreatic secretion and slowing the movement of chyme. In addition, NT can contract the gall bladder and enhance the enterohepatic circulation (EHC) of bile acids to promote micelle formation. Our recent finding that NT enhanced and an NT antagonist inhibited [(3)H]taurocholate ([(3)H]TC) absorption from proximal rat small intestine indicated a role for endogenous NT in the regulation of EHC. Here, we postulate the involvement of intestinal mast cells in the TC uptake process and in the stimulatory effect of NT. In anesthetized rats with the bile duct cannulated for bile collection, infusion of NT (10 pmol.kg(-1).min(-1)) enhanced the [(3)H]TC recovery rate from duodenojejunum by 2.2-fold. This response was abolished by pretreatment with mast cell stabilizers (cromoglycate, doxantrazole) and inhibitors of mast cell mediators (diphenhydramine, metergoline, zileuton). In contrast, mast cell degranulators (compound 48/80, substance P) and mast cell mediators (histamine, leukotriene C(4)) reproduced the effect of NT. N(G)-nitro-l-arginine methyl ester enhanced and l-arginine inhibited basal and NT-induced TC uptake, consistent with the known inhibitory effect of nitric oxide (NO) on mast cell reactivity. These results argue that basal and NT-stimulated TC uptake in rat jejunum are similarly dependent on mast cells, are largely mediated by release of mast cell mediators, and are subject to regulation by NO.     

Histamine release by neurotensin in the rat hindquarter: structure-activity studies

Histamine releasing effects of neurotensin (NT) and several NT fragments and structural analogues were measured in the rat perfused hindquarter. The results show that the chemical groups responsible for histamine release are located in the C-terminal sequence Arg9-Pro10-Tyr11-Ile12-Leu13-OH. Both the spatial configuration and positive charge of Arg8 and Arg9 appear to contribute to the histamine releasing effect of NT. Optimization of the histamine releasing effect of NT requires both a free C-terminal carboxyl group and the presence in position 11 of NT of an aromatic residue, with the L-configuration, bearing an heteroatom capable of hydrogen bonding with the receptor. The results indicate that the structural requirements of NT to induce histamine release from the rat perfused hindquarter are similar to those involved in other peripheral biological actions of NT.     

Effect of disodium cromoglycate on mast cell-mediated immediate-type allergic reactions

We investigated the effect of disodium cromoglycate (DSCG) on mast cell-mediated immediate-type hypersensitivity. DSCG inhibited systemic allergic reaction induced by compound 48/80 dose-dependently. Passive cutaneous anaphylaxis was inhibited by 71.6% by oral administration of DSCG (1 g/kg). When DSCG was pretreated at concentration rang from 0.01-1000 g/kg, the serum histamine levels were reduced in a dose dependent manner. DSCG also significantly inhibited histamine release from rat peritoneal mast cell (RPMC) by compound 48/80. We confirmed that DSCG inhibited compound 48/80-induced degranulation of RPMC by alcian blue/nuclear fast red staining. In addition, DSCG showed a significant inhibitory effect on anti-dinitrophenyl IgE-mediated tumor necrosis factor-alpha production. These results indicate that DSCG inhibits mast cell-mediated immediate-type allergic reaction.     

Release of histamine and adrenaline in vivo following intravenous administration of neurotensin

Plasma histamine levels of rats anesthetized with pentobarbital sodium were significantly increased by intravenous administration of neurotensin (NT, 1 nmole/kg) with the maximum effect at 3 min, and a return to the initial levels in 20 min. Treatment of animals with compound 48/80 or disodium cromoglycate completely inhibited the elevation of histamine level by NT, however, treatment with reserpine or diphenhydramine and adrenalectomy did not affect the elevation. Plasma adrenaline levels increased transiently 1 min after NT injection, and adrenalectomy and treatment with compound 48/80 or diphenhydramine markedly reduced the elevation of adrenaline levels after NT injection. Plasma levels of noradrenaline were unchanged upon NT injection. These results provide direct evidence of the release of endogenous histamine and adrenaline following NT administration, and suggest the contribution of these amines to the NT-induced triphasic blood pressure responses (the first depressor, second pressor and third depressor responses) reported previously.     

Amomum xanthiodes inhibits mast cell-mediated allergic reactions through the inhibition of histamine release and inflammatory cytokine production

In this study, we investigated the effect of Amomum xanthiodes (Zingiberaceae) extract (AXE) on the mast cell-mediated allergy model and studied the possible mechanism of action. We found that AXE inhibited compound 48/80-induced systemic reactions and plasma histamine release in mice. Additionally, AXE decreased immunoglobulin E (IgE)-mediated local allergic reactions and passive cutaneous anaphylaxis (PCA), and AXE dose-dependently attenuated the release of histamine from rat peritoneal mast cells (RPMC) activated by compound 48/80 or IgE. The amounts of AXE needed for inhibition of compound 48/80-induced plasma histamine release and PCA were similar to disodium cromoglycate, the known anti-allergic drug. We found that AXE increased the cAMP levels and decreased the compound 48/80-induced intracellular Ca2+. Furthermore, AXE attenuated the phorbol 12-myristate 13-acetate (PMA) plus calcium ionophore (A23187)-stimulated tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6 secretion in human mast cells. The inhibitory effect of AXE on the proinflammatory cytokines was nuclear factor-kappaB (NF-kappaB)-dependent. In addition, AXE decreased PMA plus A23187-induced degradation of IkappaBalphaand the nuclear translocation of NF-kappaB. Our findings provide evidence that AXE inhibits mast cell-derived immediate-type allergic reactions, and that cAMP, intracellular Ca2+, proinflammatory cytokines, and NF-kappaB are involved in these effects.     

Inhibition of compound 48--80 induced histamine liberation from mast cells by triton X-100]

Triton X-100 at concentrations preceding those which liberated histamine, produced dose-dependent inhibition of compound 48/80-induced histamine release from rat mast cells. Triton X-100 (0.00002 1/1) depleted ATP content in the mast cells and blocked compound 48/80-induced histamine release. The inhibition of compound 48/80-induced histamine release and depletion of the ATP content in the mast cells was reversed by glucose (10 mmole). It is concluded that inhibition by Triton X-100 of histamine release induced by compound 48/80 is dependent on inhibition of energy production.     

Compound 48/80 inhibits neurotensin-induced hypotension in rats

The intravenous injection of neurotensin (NT) (0.4 and 1.1 nmoles/kg) produced dose-dependent hypotensive effects in pentobarbital anesthetized rats. The acute or chronic administration of compound 48/80, a well known mast cell depletor, completely abolished the hypotensive effect of low to medium doses of NT and unmasked the previously unknown hypertensive effect of high doses (4.0 nmoles/kg) of NT. This hypertensive effect was significantly reduced by infusing the animals with [D-Trp¹¹]-NT a selective antagonist of NT. The hypotensive action of NT in control rats was also significantly reduced by pretreating the animals with disodium cromoglycate, an antiallergic drug which is believed to stabilize mast cells membranes, or with a mixture of azatadine and methysergide. The results suggest the participation of histamine, serotonin and possibly other endogenous vasoactive substances, to the hypotensive action of NT in rats. The possible origin of these mediators is discussed.     

The histologic and functional characterization of enzymatically dispersed intestinal mast cells of nonhuman primates: effects of secretagogues and anti-allergic drugs on histamine secretion

Despite the apparent involvement of gastrointestinal mast cells in hypersensitivity reactions in the mucosa, remarkably little information is available concerning the characteristics of these cells from man and higher animals. To study the characteristics of gastrointestinal mast cells from nonhuman primates, a previously described technique which uses a combination of mechanical and enzymatic methods to obtain mast cells from the tissues of rodents required modification to permit the successful dispersion of normal gastrointestinal tissues of higher animals. This modified procedure, as described in this report, appears to be relatively selective for mast cells located in the mucosal site, and typically yields ca 9 X 10(5) mast cells per gram of tissue. The mucosal mast cells obtained comprised ca 2% of the total nucleated cells, contained approximately 1 pg of histamine per cell, and stained metachromatically with toluidine blue only at low pH. The cells exhibited a dose-dependent release of histamine on challenge with goat anti-human IgE or the ionophores A23187 and Br-x537A but were refractory to the action of compound 48/80. IgE-mediated histamine release from monkey intestinal mast cells differed from that observed from rat intestinal mast cells in that release was inhibited not only by quercetin but also by theophylline. Disodium cromoglycate gave variable results. The data indicate that viable nonhuman primate mucosal mast cells can be obtained for study, and that these cells, although sharing some characteristics of mucosal mast cells from lower species, have distinct and unique properties. The availability of this nonhuman primate model for the study of mast cell function in higher animals should contribute to the understanding of mast cell-mediated diseases in man.     

Functional compartments in rat mast cells for cAMP and calcium on histamine release

The crosstalk between 3', 5'-cyclic adenosine monophosphate (cAMP), intracellular calcium, and histamine release in rat mast cells using the stimulatory effect of three different drugs, thapsigargin, sodium fluoride (NaF), and compound 48/80 were studied. Each of these drugs induces histamine release by different mechanisms. The transducting pathways modulating cAMP and intracellular calcium levels were modified by using, cholera toxin (CTX) which ADP-rybosylates Gs-protein, pertussis toxin (PTX) which ADP-rybosylates Gi-protein, and okadaic acid (OA) which inhibits phosphatases 1 and 2a. Our results show that CTX increased cAMP levels and inhibited histamine release elicited by thapsigargin and compound 48/80. The inhibitory effect of CTX on histamine release was potentiated by OA in the presence of compound 48/80 but was decreased in the presence of thapsigargin. Calcium uptake was stimulated by NaF and compound 48/80. The previous treatment with OA increased calcium uptake when combined with compound 48/80 but not with NaF. Treatment with NaF highly stimulated calcium uptake and cAMP levels only when combined with OA and CTX. These results suggest that the modulatory effect of intracellular calcium and cAMP on histamine release depend more on the crosstalk of the activated signal transducting pathway than on the final level of calcium or cAMP, further supporting the theory that rat mast cells are divided into functionally distinct compartments.     

Rapid degradation of neurotensin by stimulated rat mast cells

A RIA towards neurotensin (NT) using C-terminal- and N-terminal-specific antisera was used to study degradation of this tridecapeptide by isolated rat mast cells. Incubation of NT (10 μM) with peritoneal or pleural mast cells resulted in a rapid loss of NT immunoreactivity (iNT), as measured by C-terminal-directed antiserum, with little effect on N-terminal iNT. The rate of the reaction was faster with pleural cells (T_1/2, 30 s) than with peritoneal cells (T_1/2, 180 s) and was > 10-fold slower in the presence of metabolic poisons. The enzyme(s) involved is most likely released from the cells during secretion, as NT was degraded by media conditioned by compound 48/80-stimulated mast cells 40–60 times faster than by media from unstimulated cells. This degradation by conditioned media was concentration dependent, pH dependent, and temperature sensitive. HPLC analyses indicated a near stoichiometric conversion of NT to NT(1–12) (66%) and NT(1–11) (34%) after incubation for 10–30 s with conditioned media. By 30 min only NT(1–11) and NT(1–10) were present. Phenanthroline (1 mM), an inhibitor of carboxypeptidase, prevented the loss of C-terminal iNT and the generation of NT(1–12) and NT(1–11). While NT(1–12) was effective in releasing histamine from mast cells in vitro and increasing vascular permeability in vivo, NT(1–11) was not. These results suggest that carboxypeptidase-like enzyme(s) could modulate the level and form of NT-related peptides in various states involving activation of mast cells.     

Effect of interleukin-1 receptor antagonist (IL-1RA) on histamine and serotonin release by rat basophilic leukemia cells (RBL-2H3) and peritoneal mast cells

Recently, it has been appreciated that cultured mast cells are significant sources of cytokines. However, the role of interkeukin-1 (IL-1) on mast cells and/or basophil degranulation is still unclear. In this report we provide evidence that rat basophilic leukemia cells (RBLC) cultured with a natural inhibitor of IL-1, interleukin-1 receptor antagonist (IL-1RA) (500 ng/ml) for 48 h, strongly inhibited the spontaneous release of serotonin (5HT) and histamine (from 22.50 to 43.49%), compared to untreated cells (control). When IL-1RA-treated and untreated RBLC were stimulated with a secretagogue (anti-IgE), no difference was found in the percent of 5HT and histamine release. Moreover, in another set of experiments using rat peritoneal mast cells (RPMC) treated and untreated with IL-1RA, we found that IL-1RA did not affect the release of 5HT or histamine, even when the secretagogue anti-IgE or compound 48/80 (C48/80) were used. The present studies describe an additional biological activity of IL-1RA, inhibiting histamine and 5HT release from RBLC cultures.Abbreviations IL-1 interleukin-1 - RA receptor antagonist - 5HT serotonin - RBLC rat basophilic leukemia cells - RPMC rat peritoneal mast cells - IgE immunoglobulin E - Fc immunoglobulin E receptor - CPM counts per minute - BSA bovine serum albumin - C48/80 compound 48/80 - TNF tumor necrosis factor     

Evidence of an adriamycin binding site in the secretory granules of the mast cell

Adriamycin induced significant non-cytotoxic histamine release from rat peritoneal mast cells to which the drug showed a very high affinity. The relationship between adriamycin-induced exocytosis and its uptake by purified rat peritoneal mast cells was studied. Adriamycin induced histamine release and was highly concentrated in mast cells at 37 degrees C but not at 0 degrees C. However, if exocytosis was provoked by other secretagogues like compound 48/80, protamine, concanavalin A, and ionophore A23187, and cells were then treated with adriamycin at 0 degrees C, the concentrations of the antineoplastic drug significantly increased. Adriamycin binding to purified granular material was similar to that of intact cells treated at 37 degrees C, but was not modified by metabolic inhibitors, extremes of temperature (0 or 45 degrees C) or by the carboxylic ionophore monensin. On the contrary, sodium cromoglycate limited adriamycin binding to granular materials as well. In addition, sodium cromoglycate, but not monensin, displaced the antineoplastic drug from mast cells, even when added after adriamycin. We conclude that the high affinity of adriamycin for mast cells is ascribable to the externalization of a granular binding site, as a consequence of the exocytotic process. The experiments with sodium cromoglycate suggest that this binding site could be in common with the antiallergic drug.     

Calcium requirement for the inhibition by theophylline of histamine release from mast cells

When added to Ca2+-free Hanks' solution, Ca2+ (0.1-2.5 mM) had no significant effect on antigen-induced histamine release from rat mast cells, but Sr2+ (1.0-3.0 mM) dose-dependently increased the release. Ba2+ (1.0 and 2.0 mM) also enhanced the release. Ca2+ and Ba2+ inhibited compound 40/80-induced histamine release, in a dose-dependent manner. In ordinary Hanks' medium, theophylline and 3-isobutyl-1-methylxanthine (IBMX) dose-dependently inhibited the antigen-induced histamine release but these drugs were ineffective in Ca2+-free medium. Theophylline (1.0 mM) also inhibited compound 48/80-induced histamine release in the presence but not absence of Ca2+. There was an optimal Ca2+ concentration for the theophylline effect. Sr2+ but not Ba2+ could substitute for Ca2+ in supporting the theophylline effect. Theophylline (1.0 mM) and IBMX (1.0 mM) increased mast cell cyclic AMP levels both in the presence and absence of Ca2+. These results suggest that Ca2+ is required in the interaction of theophylline and specific sites on mast cells or in the mast cell response to theophylline which probably does not involve the cyclic AMP increase and is linked to the inhibition of histamine release.     

Stimulation by nitric oxide of gastric acid secretion in bullfrog fundic mucosa in vitro.

We examined the effect of NO on acid secretion in vitro using isolated preparations of Bullfrog stomach. The bullfrog fundic mucosa was bathed in unbuffered Ringer solution gassed with 100% O2 on the mucosal side and HCO3- Ringer's solution gassed with 95% O2/5% CO2 on the serosal side, and the acid secretion was measured at pH 5.0 using the pH-stat method and by adding 5 mM NaOH. Serosal addition of a NO donor NOR-3 (10(-5) approximately 10(-3) M: (+/-)-(E)-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexnamine) caused an increase of acid secretion in a dose-dependent manner, the effect lasting about 1 hr and reaching a maximal level of 2-fold the basal values. The acid stimulatory effect of NOR-3 was mimicked by another NO donor SNAP (10(-3) mol/L: S-nitroso-O-N-acetyl-penicillamine) and markedly and markedly inhibited by prior administration of cimetidine (10(-5) mol/L) as well as compound 48/80 (the mast cell degranulator). Likewise, the increased acid response to NOR-3 was significantly mitigatd by pretreatment with carboxy-PTIO (a NO scavenger) or superoxide dismutase (SOD), but not by indomethacin or methylene blue (a guanylyl cyclase inhibitor). Neoither L-NAME, L-arginine nor dibutyryl guanosine-3',5'-cyclic monophosphate (dbcGMP) has any effect on the basal acid secretion. Serosal addition of NOR-3 caused a significant increase in the luminal release of histamine, and this response was inhibited by pretreatment with either compound 48/80, carboxy-PTIO or SOD. These results suggest that the NO donor increases gastric acid secretion in the isolated frog stomach in vitro, and this action is mediated by endogenous histamine released from mast cells, the process being cGMP-independent but requiring the presence of superoxide radicals. In addition, it was speculated that the histamine releasing action of NO may be due to peroxynitrite produced by NO and superoxide radicals.     

Modulation of cyclic AMP in purified rat mast cells. II. Studies on the relationship between intracellular cyclic AMP concentrations and histamine release.

Changes in intracellular and extracellular rat mast cell adenosine 3':5' monophosphate (cAMP) concentrations during stimulation of histamine release by 48/80 were studied. There was a rapid and progressive fall in intracellular cAMP beginning within 10 sec after the addition of 48/80. The lowest cAMP values were obtained at 10 min, with return to control levels by 30 min. The fall in cAMP was dose-related with progressive decreases in 10-min cAMP measurements as the 48/80 concentration was increased from 0.25 to 1.00 mug/ml. There was a graded increase in histamine release over the same concentration range. Attempts to demonstrate significant amounts of cAMP in the medium during 48/80 stimulation were unsuccessful, indicating that the changes in cAMP intracellularly are not due to altered cellular permeability. There was a general correlation between the ability of pharmacologic agents to sustain high intracellular levels of cAMP in the presence of 48/80, and inhibition of histamine release. Theophylline (20 mM) which increased cAMP levels 2- 3-fold prevented a detectable decrease in cAMP after 1 mug/ml 48/80 (measured at 10 min) and almost completely inhibited histamine release. Prostaglandin E1 (27 muM) also raised cAMP levels, decreased the 48/80-induced fall in cAMP (by 42%). Epinephrine increased mast cell cAMP levels, but did not prevent the subsequent 48/80-induced decrease in cAMP and did not inhibit histamine release. Carbamylcholine (1 nM), adenine (1 muM), and diazoxide (10 muM) lowered mast cell cAMP and potentiated 48/80 induced release. In view of previous studies from this laboratory indicating that 48/80 stimulates mast cell phosphodiesterase, it seems likely that the 48/80-induced fall in cAMP is due, at least in part, to increased cAMP destruction. Since agents which prevent the fall in cAMP inhibit histamine release, it is apparent that cAMP is an important part of the control mechanism of histamine secretion. On the other hand, it cannot be concluded that a decrease in cAMP alone is sufficient to produce a response since carbamylcholine, diazoxide, and adenine which lower cAMP do not alter histamine release unless 48/80 is also present.     

Inhibition of non-cytotoxic histamine liberation from isolated rat mast cells by antihistaminic preparations]

Phenothiazines (chlorpromazine and promethazine) and antihistaminic quinuclidine derivatives [phencarol, quinuclidyl-3-di-(o-tolyl) carbinol, hydrochloride quinuclidyl-3-di-(o-methoxyphenyl) carbinol--HQMC] at concentrations preceding the histamine-releasing ones inhibited the compound 48/80-induced histamine release from the isolated rat mast cells. HQMC inhibited histamine release induced by selective liberators (compound 48/80, MCD-peptide, specific antigen), but potentiated histamine release induced by nonselective liberators (chlorpromazine, tryton X-100). The inhibition by HQMC of histamine release induced by compound 48/80 increased during 1 min and was reversible. The inhibitory effect of all the compounds tested was partially counteracted by glucose.     

Observations of Forsythia koreana methanol extract on mast cell-mediated allergic reactions in experimental models

To explore effects of Forsythia koreana methanol extract (FKME) on mast cell-mediated allergic and inflammatory properties, the effect of FKME was evaluated on compound 48/80-induced systemic anaphylaxis, ear swelling, and anti-dinitrophenyl (DNP) immunoglobulin E (IgE)-induced passive cutaneous anaphylaxis (PCA). In addition, the effect of FKME was investigated on the histamine release from rat peritoneal mast cells (RPMCs) stimulated by compound 48/80, which promotes histamine release. The human mast cell line HMC-1 was stimulated by phorbol 12-myristate 13-acetate plus calcium ionophore A23187. Activated HMC-1 can produce several proinflammatory and chemotactic cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, and IL-8. Cytokine levels in the culture supernatant were measured by an enzyme-linked immunosorbent assay. Cytotoxicity by FKME was determined by a 3-(4,5-dimethylthiazol-2-yl)-diphenyl-tetrazolium bromide (MTT) assay. FKME inhibited compound 48/80-induced systemic anaphylactic shock and ear swelling in mice. When 1 g/kg FKME was pretreated or posttreated with mice, compound 48/80-induced mice morality was 50 and 66.7%, respectively. One gram per kilogram of FKME pretreatment inhibited ear-swelling responses derived from compound 48/80 by 29.75%. A PCA reaction was inhibited by 17.9%. In an in vitro model, FKME (1 mg/ml) inhibited histamine release from the RPMCs by 13.8% and TNF-α, IL-6, and IL-8 production from HMC-1 cells by 71.16% (P < 0.001), 86.72% (P < 0.001), and 44.6%, respectively. However, FKME had no cytotoxic effects on cell viability. In conclusion, FKME inhibited not only systemic anaphylaxis and ear swelling induced by compound 48/80 but also inhibited a PCA reaction induced by anti-DNP IgE in vivo. Treatment with FKME showed significant inhibitory effects on histamine, TNF-α, IL-6, and IL-8 release from mast cells.     

Application of laser interference microscopy (LIM) for investigation of the protective effect of prolyl-glycyl-proline (Pro-Gly-Pro) on mast cells

The effect of peptide prolyl-glycyl-proline (Pro-Gly-Pro) on morphometric parameters of mast cells upon their activation by compound 48/80 or synacten was investigated. Cell image, obtained by the method of laser interference microscopy (LIM), is a distribution of the optical path difference of light (OPD). It evaluates the changes of the individual components of cytoplasm (maxOPD) and the total distribution of OPD (“dry mass”). The changes of “dry mass” in cytoplasm correlate with the changes of the secreted histamine amount (?0.86). Preliminary incubation of mast cells with Pro-Gly-Pro (6 × 10^?5 M) did not change the area, the state of the individual components of the cytoplasm (nucleus) and “dry mass” (histamine vesicles) in cells. The “dry mass” (histamine vesicles) and maxOPD decreased while the release of histamine increased upon the activation of mast cells by compound 48/80 (0.02 mg/mL). Preincubation of cells with Pro-Gly-Pro had no effect. Activation of cells by synacten (2 and 20 μM) led to the increase of the cell area and the reduction of maxOPD and “dry mass” (histamine vesicles). Preincubation of the cells with Pro-Gly-Pro prevented these changes. So, the protective effect of Pro-Gly-Pro was observed in the case of the activation of mast cells by synacten but not by compound 48/80.