Mast cell heterogeneity

Validation of antibodies for the specific detection of human TRPA1

The transient receptor potential cation channel family member ankyrin 1 (TRPA1) is a potential target for several diseases, but detection of human TRPA1 (hTRPA1) protein in cells and tissues is problematic as rigorous antibody validation is lacking. We expressed hTRPA1 in a TRPA1-negative cell line to evaluate 5 commercially available antibodies by western blotting, immunofluorescence, immunocytochemistry and flow cytometry. The three most cited anti-TRPA1 antibodies lacked sensitivity and/or specificity, but two mouse monoclonal anti-TRPA1 antibodies detected hTRPA1 specifically in the above assays. This enabled the development of a flow cytometry assay, which demonstrated strong expression of TRPA1 in human lung myofibroblasts, human airway smooth muscle cells but not lung mast cells. The most cited anti-TRPA1 antibodies lack sensitivity and/or specificity for hTRPA1. We have identified two anti-TRPA1 antibodies which detect hTRPA1 specifically. Previously published data regarding human TRPA1 protein expression may need revisiting.

Effect of propolis on mast cells in wound healing

Wound healing is divided into three phases: inflammatory, proliferative and remodeling. Mast cells participate in all these phases. The aim of the present study was to determine the effects of propolis on the population of mast cells in oral surgical wounds in comparison to the results obtained with dexamethasone. This study was prospective, in vivo, randomized, semiexperimental, quantitative and comparative animal. A circular surgical wound was made on the dorsum of the tongue of 90 hamsters divided into three experimental groups: topical application of 30% propolis alcoholic extract (Group 1); 0.1% dexamethasone in orabase cream (Group 2); and orabase cream alone (Group 3). Applications were performed every 12 h throughout the experiment. The postoperative times for killing of the animals were 1, 3, 7, 14 and 28 days. The Student's t test for independent samples was employed in the statistical analysis. In the inflammatory phase of healing, propolis caused a greater reduction in the number of mast cells on the edge and in the central region of the surgical wound in comparison to dexamethasone. Moreover, the number of mast cells on day 1 was lower in the central region of the wounds treated with the orabase cream alone in comparison to dexamethasone. In conclusion, the anti-inflammatory action of propolis mediated by mast cells was more effective than dexamethasone in the inflammatory phase of healing.

Mast Cells Appearing in Long-term Skeletal Muscle Cell Cultures of Rat

Mast cells are known to be involved in type I allergy and to be localized in almost all tissues in the body. However, they have slightly different properties depending on their tissue of residence. Although mast cells are found in skeletal muscle tissue, there have been no reports of their appearance in cultured skeletal muscles. We report here that mast cells appear in long-term cultures of skeletal muscles from neonatal rats and rat fetuses. When muscle cells were disseminated and cultured in minimum essential medium with 10% fetal calf serum and 10% horse serum, oval cells containing large granules started to appear on myotube sheets at 5 days of culture. These oval cells continued to proliferate for 2-3 months, and showed immunoreactivity for histamine, tryptase, Fc(epsilon)RI, and c-kit. They showed metachromatic staining with 0.5% toluidine blue at pH 0.5 and were stained with both Alcian blue and safranin. Biochemically measured histamine content per dish was significantly higher in 2-month than in 5-day culture. From these results, we concluded that these oval cells were mast cells. Because proteases from mast cells have been reported previously to affect myoblast proliferation, the present findings suggest that there may be some interaction between mast cells and muscle cell proliferation or differentiation. The present finding that mast cells are easily obtained from ordinary skeletal muscle cultures provides a useful method for the study of the diverse functions of mast cells.

Lack of neurokinin-1 receptor expression affects tissue mast cell numbers but not their spatial relationship with nerves

A spatial association between mast cells and nerves has been described in both the gastrointestinal and genitourinary tracts. However, the factors that influence the anatomic relationship between mast cells and nerves have not been completely defined. It has been suggested that the high-affinity receptor for substance P [neurokinin-1 (NK1)] might modulate this interaction. We therefore assessed mast cell-nerve relationships in tissues isolated from wild-type and NK1 receptor knockout (NK1-/-) mice. We now report that, in the complete absence of NK1 receptor expression, there is a significant increase in the number of mast cells without a change in the anatomic relationship between mast cell and nerves in stomach and bladder tissues at the light microscopic level. We next determined whether transplanted mast cells would maintain their spatial distribution, number, and contact with nerve elements. For this purpose, mast cell-deficient Kit(W)/Kit(W-v) mice were reconstituted with wild-type or NK1-/- bone marrow. No differences in mast cell-nerve contact were observed. These results suggest that NK1 receptor expression is important in the regulation of the number of mast cells but is not important in the interaction between mast cells and nerves. Furthermore, the interaction between mast cells and nerves is not mediated through NK1 receptor expression on the mast cell. Further studies are needed to determine the molecular pathway involved in mast cell migration and interaction with nerve elements, but the model of reconstitution of Kit(W)/Kit(W-v) mice with mast cells derived from different genetically engineered mice is a useful approach to further explore these mechanisms.

Effects of quinotolast, a new orally active antiallergic drug, on experimental allergic models

The effects of a new antiallergic drug, quinotolast [sodium 5-(4-oxo-1-phenoxy-4H-quinolizine-3-carboxamido)tetrazolate monohydrate], were studied and compared with those of tranilast, amlexanox, pemirolast, repirinast and disodium cromoglycate (DSCG) in experimental allergic models. Quinotolast potently inhibited such type I allergic reactions as passive cutaneous anaphylaxis (PCA) and anaphylactic bronchoconstriction in rats by both intravenous and oral dosing. All of these effects were stronger than those of the reference drugs tested. Quinotolast inhibited histamine release from rat peritoneal cells, but it had no antagonistic effect on histamine-, serotonin-, platelet activating factor- or bradykinin-induced cutaneous reactions in rats. Moreover, it was clearly demonstrated that quinotolast and DSCG had a cross tachyphylaxis to inhibit PCA in rats, suggesting that these drugs, at least in part, share the same mechanism of action. Furthermore, quinotolast potently inhibited PCA in guinea pigs in which DSCG and other reference drugs showed poor inhibitory activity. Quinotolast also showed stronger inhibitory effects on histamine and peptide leukotrienes release from guinea pig lung fragments or mouse cultured mast cells than the other drugs tested. Thus, the effect of quinotolast on type I allergic reaction would seem to be based on an inhibition of mediator release from inflammatory cells including mast cells. The results suggest that quinotolast will be beneficial in the treatment of type I allergy-related diseases.

Influence of indomethacin and L-cysteine on histamine and peptidoleukotriene release from superfused tracheas taken from guinea pigs passively sensitized with IgG1 and IgE antibodies

We have previously reported differences in mediator release during equivalent levels of antigen (Ag)-induced smooth muscle contraction of guinea pig pulmonary tissues after passive sensitization with IgG1 versus IgE antibodies (Abs). In the present study, we have examined the influence of indomethacin (5 x 10(-6) mol/L) and L-cysteine (3 or 10 mmol/L) on mediator release from superfused trachea taken from guinea pigs passively sensitized with IgG1 or IgE Ab 1 day before in vitro studies. Tissues were challenged with Ag (oxazolone-human serum albumin conjugate), and contractions and superfusate histamine and peptidoleukotrienes were monitored at discrete time intervals thereafter. Superfusate mediator contents were determined by spectrophotofluorimetry (histamine) and RAST (peptidoleukotrienes). The profiles of peptidoleukotrienes were examined with high-pressure liquid chromatography. At equivalent levels of contraction, significantly less histamine and peptidoleukotrienes were found in superfusate samples after sensitization with IgE Abs. None of the drug pretreatments significantly altered Ag-induced histamine release after IgG1 or IgE sensitization. Indomethacin resulted in an increase in total measurable peptidoleukotrienes found only after IgG1 receptor activation, but it did prolong tracheal contractions with both Abs. L-cysteine, 10 mmol/L, resulted in an increase in total measurable superfusate peptidoleukotriene content under all experimental conditions. The percentage increase in peptidoleukotriene content from that found without drug pretreatment was larger in the case of IgE compared to IgG1 sensitization. During early time periods, after Ag challenge, measurable peptidoleukotriene levels in superfusate samples were similar for both Abs in the presence of L-cysteine, 10 mmol/L. These data suggest that there is a differential pattern of peptidoleukotriene metabolism after activation of IgG1 versus IgE receptors in guinea pig trachea.

Trigeminal sensory fiber stimulation induces morphological changes reflecting secretion in rat dura mater mast cells

Mast cells are involved in allergic reactions, but may also participate in neurogenic inflammation. The morphology of mast cells in rat dura mater and tongue was evaluated by histochemistry, as well as by scanning and transmission electron microscopy following unilateral trigeminal ganglion stimulation (5 min, 5 Hz, 5 ms, and 0.02, 0.1 or 1.0 mA). Mast cells in dura and tongue of normal animals were numerous, perivascular and often in close proximity to nerve fibers. After 5 min of electrical stimulation, mast cells contralateral to the stimulation showed histochemical characteristics of normal peripheral tissue mast cells (Safranin-positive), and by electron microscopy appeared homogeneous with numerous intact electron-dense granules. On the stimulated side, however, the staining characteristics of mast cells showed changes indicating progressive intracellular loss of their granular content. In addition, the total number of stainable mast cells decreased at all three stimulus intensities, but reached significance only at 0.1 and 0.02 mA. Ultrastructural evidence of granule changes consistent with secretion were observed although degranulation was not observed until 20 min after stimulation. There were no mast cell changes after electrical trigeminal stimulation in adult rats treated as neonates with capsaicin to destroy small caliber sensory afferent axons. These results suggest that mast cells may secrete in response to electrical stimulation of trigeminal axons, possibly mediated by antidromic release of neuropeptides, and may participate in the development of neurogenic inflammation.

Study on staining methods for mast cells in the nasal mucosa

Mast cells are widely distributed in various organs. Two classes of mast cells, the mucosal mast cell (MMC) and the connective tissue mast cell (CTMC), have been shown to exist in the intestine of experimental animals. In the present study, we investigated the method of staining suitable for observing the mast cells distributing in the nasal mucosa, and also examined by the use of two fixatives whether the mast cells have properties of MMC or those of CTMC. A neutral buffered formalin solution and Carnoy's solution were used as fixative. For staining, five solutions, i.e., toluidine blue (TB) solution (pH 0.5, 2.5, and 4.0), 0.4 M MgCl2-alcian blue (AB) solution, and naphthol AS-D chloracetate (NAS-DC) solution, were tested. In the specimen fixed with Carnoy's fixative, staining with pH 0.5 TB showed the largest number of mast cells in all mucosal layers, particularly in the epithelial layer. The number of these mast cells agreed with that of the cells positive to pH 0.5 AB and also with that of the tryptase-positive cells stained immunohistochemically with a mouse monoclonal antitryptase antibody. Compared with formalin-fixed specimens, those fixed with Carnoy's fixative and stained with pH 0.5 TB showed significantly (p less than 0.01) many mast cells in the epithelial layer and in the subepithelial layer of lamina propria. To identify mast cells in the nasal mucosa with nasal allergy, fixation with Carnoy's fixative and staining with pH 0.5 TB were found to be most effective and simplest.(ABSTRACT TRUNCATED AT 250 WORDS)

Metachromatic cells in nasal mucosa after allergen challenge

Metachromatic cells in the nasal mucosa were studied in relation to symptoms in 16 schoolchildren and 11 adults with hay fever who were challenged with pollen outside the pollen season, using either a gentle scraping-cytocentrifugation method for collection of mucosal specimens or biopsies. There was a temporary redistribution of metachromatic cells towards the mucosal surface appearing 5-24 h after challenge, with a correlation between the quantity of metachromatic cells and symptom scores. Thus, a single exposure to high doses of allergen may contribute to priming in susceptible individuals.

Mast cells in human lungs

Mast cells were stained deeply in human lung tissue with acidic toluidine blue to obtain maximum numbers possible in paraffin sections. One hundred high-power fields were counted per section, and mean and median values summarized as mast cells per mm2. Immersion-fixed samples of fresh lung tissue (not bronchi) were taken as controls from seven patients after surgery, and showed mean values of 44.7 mast cells per mm2 after formalin fixation, and 51.9 per mm2 after Carnoy's fixative. Mast cell heterogeneity may explain these differences, but so could random variation between counts. In two patients with extrinsic allergic alveolitis (hypersensitivity pneumonitis), fresh lung tissue from open lung biopsies showed raised values of 90.8 and 101.9 mast cells per mm2, matching the high mast cell counts reported in bronchopulmonary lavage fluid in the condition. Control post-mortem lung tissue from two patients dying of non-pulmonary diseases showed mean values of 26.1 and 50.6 mast cells per mm2. Post-mortem lung tissue from three patients dying of asthma showed very low mean values of 4.7, 5.7, and 5.9 mast cells per mm2. Low mast cell counts due to severe degranulation have been reported before in the bronchi in asthma deaths, but not, to our knowledge, in the lung parenchyma. This finding implies a wider area of mediator release, and helps to explain the severity of the acute attack, and the fatal outcome.

Modulation of the adoptive immune response in mice by histamine

The immunomodulatory actions of histamine in mice were examined by a combined in vitro/in vivo approach. Spleen cells from mice were incubated between 2 and 24 hours with histamine (10(-12)-10(-3) M) under conditions which prevent a change of the free histamine concentration. The cells were subsequently transferred to sublethally irradiated syngenic mice in order to measure the adoptive IgM response. Only stimulatory effects of histamine were found at NMRI mice. However, both stimulatory and inhibitory actions were observed at different histamine concentrations if mice of the strains AB or XVII were used. The graft versus host reaction was measured after transfer of histamine treated spleen cells (strain XVII) to neonatal F1 (XVII X B10.LP) hybrid mice and revealed both suppressive and stimulatory effects of histamine at different concentrations. A maximal expression of the immunomodulatory effects of histamine was found after 8 hours of preincubation with the donor cells. The action of selective histamine antagonists and cell separation experiments indicated that the effect of histamine on the adoptive IgM response was mediated by H2-receptors on spleen T-cells. Summarizing, the results indicate that low histamine concentrations elicit bidirectional immunomodulatory effects in mice which vary considerably among different strains.

B-cell stimulation by T-cell-secreted proteoglycan

We have further characterized a recently described B-cell stimulatory factor that contains chondroitin sulfate proteoglycan and 70- to 75-kDa protein, both of which are secreted by T cells and coisolate (T-cell proteoglycan fraction, T-PGF). Using T-PGF isolated from a T-cell hybridoma (T14), it was observed that the association between B-cell stimulatory activity and CSPG is stable and comigrates on Sephacryl S-200 columns eluted at high salt concentrations (1.5 M NaCl) and on CsCl gradients. The T-PGF stimulated larger numbers of low-density (activated) B cells, but better relative PFC formation occurred in high-density (resting) B-cell fractions. It is proposed that the B-cell stimulatory activity of T-PGF is, in fact, chondroitin sulfate proteoglycan.

Pathway-specific patterns of the co-existence of substance P, calcitonin gene-related peptide, cholecystokinin and dynorphin in neurons of the dorsal root ganglia of the guinea-pig

The co-existence of immunoreactivities to substance P (SP), calcitonin gene-related peptide (CGRP), cholecystokinin (CCK) and dynorphin (DYN) in neurons of the dorsal root ganglion (DRG) of guinea-pigs has been investigated with a double-labeling immunofluorescence procedure. Four main populations of neurons could be identified that contained different combinations of these peptides and had distinctive peripheral projections: (Neurons that contained immunoreactivity to SP, CGRP, CCK and DYN were distributed mainly to the skin. Neurons with immunoreactivity to SP, CGRP and CCK, but not DYN, were distributed mainly to the small blood vessels of skeletal muscles. Neurons with immunoreactivity to SP, CGRP and DYN, but not CCK, were distributed mainly to pelvic viscera and airways. Neurons containing immunoreactivity to SP and CGRP, but not CCK and DYN, were distributed mainly to the heart, systemic blood vessels, blood vessels of the abdominal viscera, airways and sympathetic ganglia. Other small populations of DRG neurons containing SP, CGRP or CCK alone also were detected. Perikarya containing these combinations of neuropeptides were not found in autonomic ganglia. The peripheral axons of neurons containing immunoreactivity to at least SP and CGRP were damaged by chronic treatment with capsaicin. However, some sensory neurons containing CCK alone were not affected morphologically by capsaicin. These results clearly show that individual DRG neurons can contain many different neuropeptides. Furthermore, the combination of neuropeptides found in any particular neuron is related to its peripheral projection.

Antiallergic activity of loratadine, a non-sedating antihistamine

Loratadine is a new non-sedating antihistamine. The present studies compared loratadine and terfenadine, another non-sedating antihistamine, for their ability to inhibit the bronchial response to histamine and other autacoids which have been implicated as contributing to the symptoms of an allergic reaction. In addition, the two antihistamines were evaluated in models of immunologically mediated allergic reactions. Loratadine is a more potent inhibitor of histamine-induced bronchospasm in guinea pigs than is terfenadine. Both antihistamines exhibit marked antiserotonin activity at doses 10 times their antihistamine ED50 values. In contrast, loratadine and terfenadine produce little or no inhibition of the bronchial responses to methacholine, leukotriene C4 or platelet-activating factor. An allergic bronchospasm in guinea pigs is inhibited by loratadine (ED50 = 0.40 mg/kg, p.o.) and terfenadine (ED50 = 1.7 mg/kg, p.o.). The bronchospasm associated with allergic anaphylaxis in rats is significantly inhibited by 10 mg/kg, p.o. loratadine and 30 mg/kg, p.o. terfenadine. Loratadine exhibits antiallergy activity in vitro. At micromolar concentrations, loratadine inhibits the release of histamine from Con A and A23187-stimulated rat peritoneal mast cells and the release of histamine and leukotriene C4 from a Con A-stimulated cloned murine mast cell line.

Cutaneous mast cell heterogeneity: response to antigen in atopic dogs

Because mast cells (MCs) in skin of atopic dogs are heterogeneous with respect to tissue fixation and staining properties, we determined the effect of antigen on each type of MC in vivo. Skin biopsies were done in anesthetized, ragweed-sensitized dogs before and at 1, 3, 6, and 24 hours after intradermal injections of ragweed antigen (n = 5) or glycerin diluent (n = 4). In each case, one biopsy specimen was fixed with formalin, and a second specimen from an adjacent abdominal site was fixed with basic lead acetate. In sections stained with Alcian blue, 49.7% more MCs (p less than 0.05) were detected in tissue fixed with basic lead acetate ("typical" plus "atypical" MCs: 2916 +/- 581/mm3; mean +/- SEM) than in tissue fixed with formalin ("typical" MCs: 1955 +/- 537/mm3). After antigen, the number of "typical" MCs detectable in tissue sections progressively decreased during the 24-hour period, whereas the number of "atypical" MCs was lowest at 1 hour and had increased at 24 hours. After diluent, MC numbers did not change significantly over time. A late-phase response (LPR), detected clinically as induration and edema, was present 6 hours after antigen in four of five dogs, but LPR was not detected after diluent. The size of LPR was correlated (r = 0.85; p less than 0.05) with the decrease in the number of "typical" MCs at 6 hours. We conclude that the response of the "typical" and "atypical" MC to antigen in vivo differs markedly. The "atypical" MCs participate in the early, acute response to antigen, and the "typical" MCs may be associated with the development of the LPR.

Intestinal immunity and inflammation: recent progress

The previous sections illustrate that we are still defining (a) which sets of lymphoid cells are present in the intestine and which are not, (b) which sets are peculiar to the intestine, and (c) how the sets that are there function in the intestinal microenvironment. An understanding of the latter point is going to require knowledge of how these sets communicate with and regulate one another via cell surface molecules such as MHC class I and class II molecules, and via soluble mediators or lymphokines. The recent advances in various technologies make this a particularly exciting time in this field because the tools are now available to address and answer some of these basic and important questions in mucosal immunology. At the same time these advances hold great promise for our eventual understanding of chronic inflammatory diseases of the intestine. As was mentioned at the outset, the immune system has considerable power for both protection and destruction. It remains a puzzle how this latter potential is contained and controlled in the intestine of most individuals, such that they do not have inflammatory disease even in the setting of intense stimulation by substances, such as endotoxin, that are phlogistic elsewhere in the body. An answer to the question of why everyone does not have intestinal inflammation could provide new insights into the mechanisms involved in chronic intestinal inflammatory diseases. The recent advances just detailed, as well as others sure to come, suggest that it is only a matter of time before such questions are answered.

Heterogeneity of calcium channels in mast cells and basophils and the possible relevance to pathophysiology of lung diseases: a review

Calcium plays a critical role in the formation and secretion of a wide variety of chemical mediators. Calcium slow-channel blockers, e.g. nifedipine and verapamil, have been shown to inhibit the synthesis of SRS (SRS-A, leukotrienes) in human and guinea pig lung tissue, thromboxane A2 formation in rat lung and platelet activating factor in human neutrophils. Verapamil and nifedipine also prevent the release of lysosomal enzymes from rabbit and human polymorphonuclear neutrophils. Calcium-channel blockers produce variable inhibitory effects on allergic and nonallergic histamine secretion. Ca++-entry blockers also inhibit the Ca++ uptake (influx) into mast cells. Many of these inhibitory effects of Ca++ antagonists are antagonized by an increased extracellular Ca++ ion concentration. The magnitude of the inhibitory influences of Ca++-channel blockers on allergic and nonallergic release of chemical mediators appears to depend on the cell source, species, nature and the concentration of the secretory stimuli as well as on the composition and pH of buffers and the concentration of Ca++-entry blockers used. The data summarized in this review suggest the existence of a functional heterogeneity of Ca++ channels in leukocytes, mast cells and basophils. Interference with the Ca++-dependent steps involved in the formation and/or release of chemical mediators appears to be the primary mode of action for Ca++-channel blockers in these cells. The differential effects of Ca++ antagonists on Ca++-dependent activation of phospholipase A2,5-lipoxygenase, and calmodulin (or other intracellular Ca++-binding proteins) in different cell types (mast cells, basophils, leukocytes, lung tissue, etc.) may explain the variation of their effectiveness in inhibiting the synthesis/release of chemical mediators and antagonizing bronchoconstriction in response to diverse stimuli. During the process of hypersensitization and in immediate hypersensitivity diseases, Ca++ homeostasis (uptake, mobilization, distribution, relocation, etc.) may be altered in leukocytes (mast cells, basophils) and lung tissues. The altered Ca++ homeostasis could be responsible for the induction of airway hyperreactivity in asthmatics and for hyperreleasability of chemical mediators from leukocytes, mast cells and other cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

Unique characteristics of local responses in host resistance to mucosal parasitic infections

Because of the tremendous impact that parasitic infections have on the health and productivity of humans and domestic animals, considerable research effort has been focused upon understanding the mechanisms of host-parasite coexistence, host resistance and immunopathology. Studies have employed a range of approaches including: kinetic analysis of parasite establishment, development, fecundity and survival in naive and previously-infected hosts; correlation between parasite survival and histopathologic responses at the site of infection; vaccination with attenuated parasites or their products; cellular and serum transfer of immunity to naive or immunocompromised hosts; pharmacologic manipulation of potential mediators of host defense using agonistic and antagonistic drugs. However, it is becoming increasingly clear that to understand the mechanisms associated with host resistance and parasite survival, one must define the characteristics of the local microenvironment at the host-parasite interface. One of the approaches by which such studies can be made involves the isolation and characterization of cells derived from the local infection site. This manuscript reviews some of these studies on local aspects of mucosal immune responses in parasitic infections. Examples that will be discussed include IgA antibody, intraepithelial leukocytes from the intestine, intestinal mast cell populations, macrophages derived from bronchoalveolar lavage, and local immunoregulatory responses during respiratory and intestinal parasitic infection. These studies have established unequivocally that local responses to mucosal parasitic infection can only be appropriately investigated using cells derived from the specific microenvironment. This conclusion should encourage others to further study these local responses and to be innovative in investigating unexplored aspects of the host-parasite interface.

Contractile responses of the guinea-pig esophageal muscularis mucosae in vitro to arachidonic acid and its metabolites

The responsiveness of the guinea-pig esophageal muscularis mucosae to arachidonic acid (AA) and its cyclooxygenase and lipoxygenase metabolites was examined in vitro. AA (0.1-30 microM) produced a concentration-dependent contraction of the muscularis mucosae (mean EC50 +/- S.E.M. = 5.1 +/- 1.0 microM). The contractions in response to low concentrations of AA (0.1-3 microM) were prevented by pretreatment of the tissue with indomethacin (1-10 microM), while those in response to high concentrations (10-100 micron) were prevented by BW755C (10-100 microM). The contractile response to AA was antagonized by polyphloretin phosphate (PPP, 1-10 micrograms/ml) and by FPL 55712 (1-10 microM). All cyclooxygenase and lipoxygenase metabolites of AA tested also produced a sustained contraction of the muscularis mucosae with the following order of sensitivity; leukotriene (LT) D4 greater than LTC4 greater than prostaglandin (PG) E2 greater than PGF2 alpha greater than PGI2 greater than thromboxane B2. The responses to LTC4 and LTD4 were antagonized by FPL 55712 (0.1-1 microM), while those to PGE2 and PGF2 alpha were antagonized by PPP (3-100 micrograms/ml). The present results indicate that exogenously applied AA contracts the isolated muscularis mucosae of the guinea-pig esophagus by an indirect action via its metabolism to both PGs and LTs. The putative PG and LT receptors located in this tissue are probably similar to those in the ileal longitudinal muscle, but differ from those in the airway smooth muscle.

Homology of the rat basophilic leukemia cell and the rat mucosal mast cell

Secretory granules of the rat basophilic leukemia (RBL-1) cell, a chemically generated tumor cell line maintained in tissue culture, were shown to stain with alcian blue but not with safranin counterstain and to have sparse, small, electron-dense granules. A Mr 25,000 protein was the major [3H]diisopropyl fluorophosphate-binding protein in extracts of RBL-1 cells. Double-immunodiffusion analysis of extracts revealed immunoreactivity for rat mast cell protease (RMCP)-II, a Mr 25,000 neutral protease present in the secretory granules of rat mucosal mast cells and cultured rat bone marrow-derived mast cells, but no immunoreactivity for RMCP-I, the predominant neutral protease of rat connective tissue mast cells. By radial immunodiffusion, there was 66.8 ng of RMCP-II per 10(6) cells. Whereas rat connective tissue mast cells stain with alcian blue and safranin and contain heparin proteoglycan, rat mucosal and rat bone marrow-derived mast cells stain with alcian blue only and contain a non-heparin proteoglycan and lesser amounts of histamine. Proliferation of rat mucosal mast cells in vivo and rat bone marrow-derived mast cells in vitro requires T-cell factors, whereas no comparable requirement has been observed for connective tissue mast cells. The transformed RBL-1 tumor cells, whose growth is independent of factors other than those present in standard tissue culture medium, has previously been shown to contain predominantly chondroitin sulfate di-B proteoglycans and low amounts of histamine. The similar histology and secretory granule biochemistry of the rat mucosal mast cells, rat culture-derived mast cell, and RBL-1 cell suggest that they comprise a single mast cell subclass distinct from the rat connective tissue mast cell.