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PubMed1992

A synthetic glycoconjugate representing the genus-specific epitope of chlamydial lipopolysaccharide exhibits the same specificity as its natural counterpart.

The tetrasaccharide 3-deoxy-alpha-D-manno-2-octulosonic acid (alpha-KDO) (2----8)-alpha-KDO(2----4)-alpha-KDO(2----6)-beta GlcNAc, a partial structure of chlamydial lipopolysaccharide (LPS) representing a genus-specific epitope, was synthesized and covalently linked to bovine serum albumin, resulting in an artificial glycoconjugate antigen. Mice were immunized with the glycoconjugate to prepare chlamydia-specific monoclonal antibodies. They were selected with chlamydia-specific LPS antigens and the structurally and antigenically related Re-type LPS of a Salmonella minnesota rough mutant. Characterization of the selected antibodies was by (i) hemagglutination of sheep erythrocytes coated with recombinant chlamydia-specific LPS, (ii) inhibition by synthetic polyacrylamide derivatives containing the genus-specific epitope or partial structures thereof, (iii) enzyme immunoassay with recombinant LPS and synthetic bovine serum albumin glycoconjugates as solid-phase antigens, (iv) immunofluorescence of L929 monolayers infected with Chlamydia psittaci or C. trachomatis, and (v) Western immunoblots with glycoconjugates and LPS as the antigen. Two groups of monoclonal antibodies were obtained; the monoclonal antibodies in one group cross-reacted with chlamydial and Re-type LPS, but those of the other group were chlamydia specific. Among the latter, KDO trisaccharide-specific antibodies that had the same epitope specificity as antibodies obtained after immunization with chlamydial elementary bodies were identified; however, they exhibited a more than 100-fold higher affinity. In addition, antibodies that bound preferentially to the 2.8-linked KDO disaccharide were detected, although with lower affinity. The data show that the artificial glycoconjugate antigen is similar to its natural counterpart.

Animals↗
PubMed1993

Galaptin and galaptin-binding glycoconjugates in serum and effusions of carcinoma patients.

The objectives of this study were (1) to quantify galaptin, an endogenous lectin, and galaptin-binding glycoconjugates present in normal serum, (2) to determine if these components were altered in the serum and effusions of carcinoma patients with advanced disease, and (3) to determine if ovarian carcinoma cells synthesize and release soluble galaptin inhibitors. Serum from healthy females (n = 10) had a mean galaptin content of 96 +/- 40 ng/ml. Galaptin levels in carcinoma patient serum (n = 29) were depressed (mean 21 +/- 23 ng/ml; p < 0.0001). Galaptin was not detected in 6 of 8 ovarian carcinoma patient sera. Effusions (n = 17) had a mean galaptin content of 358 +/- 326 ng/ml. Assays involving inhibition of binding of galaptin-peroxidase conjugates to asialofetuin were carried out to evaluate the levels of galaptin-binding glycoconjugates in serum and effusions. The mean inhibition titer of normal serum (n = 12) was 75 +/- 38. Patient serum (n = 28) had an elevated inhibitor content (mean titer = 304 +/- 155; p < 0.0001). Effusions (n = 17) also had a higher inhibitor content relative to normal serum (mean titer = 247 +/- 202; p = 0.0037). Ovarian carcinoma cells isolated from effusions and cultured in vitro were shown to synthesize and release into the medium galaptin-binding glycoconjugates of molecular mass 100-200 kD. An ovarian carcinoma cell line, A121, released galaptin-binding glycoconjugates of molecular mass > or = 200 kD into the medium. The data presented show that the levels of soluble galaptin and galaptin-binding glycoconjugates in the serum of advanced cancer patients are perturbed relative to normal female serum.

Breast Neoplasms↗
PubMed2005

Treponema medium glycoconjugate inhibits activation of human gingival fibroblasts stimulated with phenol-water extracts of periodontopathic bacteria.

Oral treponemes are well-known as causative agents of periodontal diseases; however, the details have not been fully clarified. Here, we examined the effects of Treponema medium glycoconjugate on the activation of human gingival fibroblasts using phenol-water extracts from Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum subsp. nucleatum, and Actinobacillus actinomycetemcomitans. The phenol-water extracts activated human gingival fibroblasts to mediate IL-8 production, as well as IL-8 mRNA expression, phosphorylation of p38 mitogen-activated protein kinase, and expression of intercellular adhesion molecule-1. T. medium glycoconjugate exhibited no activation of human gingival fibroblasts, while phenol-water extract-induced activation of human gingival fibroblasts was clearly inhibited by T. medium glycoconjugate. Furthermore, binding of biotinylated phenol-water extracts to CD14 in the presence of LPS-binding protein was blocked with T. medium glycoconjugate. These results suggest that T. medium glycoconjugate has an inhibitory effect on host cell activation by periodontopathic bacteria caused by binding to CD14- and LPS-binding protein.

Acute-Phase Proteins↗
PubMed1988

The appearance of glycoconjugates associated with cortical granule release during mouse fertilization.

For the first time we have shown with appropriately labelled lectins that fucosyl- and sialyl-rich glycoconjugates are released into the perivitelline space of the mouse oocyte after activation by the fertilizing spermatozoon or artificial activation by the calcium ionophore A23187 or ethanol. The glycoconjugates show a punctate distribution over the oocyte surface except for the microvilli-free area overlying the second meiotic spindle from which they are absent. Their appearance in the perivitelline space is associated with the release of the cortical granule suggesting that they represent part of the cortical granule exudate. Soon after the glycoconjugates appear, they begin to aggregate. The process continues until the beginning of cytokinesis at first cleavage when a single large aggregate is found within the cleavage furrow. Most of the labelled glycoconjugates disappear by the late 2-cell stage and no evidence was found for their presence during the later preimplantation period. This technique is suitable for monitoring the kinetics of the cortical reaction in mammalian oocytes and investigating the importance of the glycoconjugates in early preimplantation period.

Animals↗
PubMed1995

Localization of a corneal basement membrane glycoconjugate in bovine eye.

Lectin histochemistry was used to analyze the ocular surface basement membrane in order to identify novel, tissue-specific glycoconjugates. Soybean agglutinin (SBA), a lectin marker for N-acetylgalactosamine residues, recognized a 130 kDa glycoconjugate in corneal but not conjunctival basement membrane. Following corneal epithelial cell wounding in vitro, the glycoconjugate was not expressed at the epithelial cell-stromal interface until 72-96 h in culture, much later than the expression of other basement membrane molecules. In epithelial cells maintained on various extracellular matrix substrates (laminin, collagen type IV, or a mixture of laminin, collagen type IV and heparan sulfate proteoglycan), the glycoconjugate localization patterns changed with time in culture from a diffuse cellular or perinuclear ring to an extensive extracellular filament network. The presence of SBA in the culture medium did not affect migration or adhesion in either the wound healing model or in culture cells. However, the presence of SBA did delay the deposition of laminin at the zone of basement membrane reformation in the wound healing model. The 130 kDa glycoconjugate is a candidate for molecules which impart a tissue-specificity to the corneal basement membrane, and which may be involved in cell-matrix interaction.

Animals↗
PubMed2005

Histochemistry of glycoconjugates in mucous cells of Salmo trutta uninfected and naturally parasitized with intestinal helminths.

Mucus secreted onto the surface of the intestine forms a physical barrier to invading parasites so that a possible attachment of helminths to the surface is prevented and their expulsion by peristalsis facilitated. In mammals, intestinal parasites induce hyperplasia and hypertrophy of intestine goblet cells and provoke changes in the mucus composition. In fish, this topic has received less attention. In the present investigation, histochemical methods were employed to compose intestinal mucous cell numbers and their glycoconjugate composition were compared by uninfected brown trout Salmo trutta and in S. trutta parasitized with Cyathocephalus truncatus or Pomphorhynchus laevis. When P. laevis was present in the intestine of the brown trout, the total mucous cell number, and the number of mucous cells containing acid or mixed glycoconjugates were significantly enhanced. No significant change in the total mucous cell number was detected in the intestine of fish parasitized with C. truncatus in comparison with uninfected brown trout. A significant increase was observed in the number of both acid (especially sulphated) and mixed glycoconjugates containing mucous cells as well as a significant decrease in the number of neutral glycoconjugates containing mucous cells. When intestinal helminths were present, the thickness of the adherent mucous gel increased. In a limited number of other fish species, the occurrence of gill and intestinal parasites has been reported to increase the mucosal glycoconjugate secretions. Our study is the first quantitative report on the effects of intestinal helminths on the density of mucous cells and mucus composition in a fish species.

Analysis of Variance↗
PubMed2000

Sulfated glycoconjugates enhance CD36-dependent adhesion of Plasmodium falciparum-infected erythrocytes to human microvascular endothelial cells.

A novel adhesive pathway that enhances the adhesion of Plasmodium falciparum-infected erythrocytes (IEs) to endothelial cells has been identified. The sulfated glycoconjugates heparin, fucoidan, dextran sulfate 5000, and dextran sulfate 500 000 caused a dramatic increase in adhesion of IEs to human dermal microvascular endothelial cells. The same sulfated glycoconjugates had little effect on IE adhesion to human umbilical vein endothelial cells, a CD36-negative cell line. The effect was abolished by a monoclonal antibody directed against CD36, suggesting that enhanced adhesion to endothelium is dependent on CD36. No effect was observed on adhesion to purified platelet CD36 cells immobilized on plastic. The same sulfated glycoconjugates enhanced adhesion of infected erythrocytes to COS cells transfected with CD36, and this was inhibited by the CD36 monoclonal antibody. These findings demonstrate a role for sulfated glycoconjugates in endothelial adherence that may be important in determining the location and magnitude of sequestration through endogenous carbohydrates. In addition, they highlight possible difficulties that may be encountered from the proposed use of sulfated glycoconjugates as antiadhesive agents in patients with severe malaria.

Animals↗
PubMed2002

Heterozygosity of CDAN II (HEMPAS) gene may be detected by the analysis of erythrocyte membrane glycoconjugates from healthy carriers.

BACKGROUND AND OBJECTIVES: Congenital dyserythropoietic anemia (CDA) type I, II, and III, is associated with abnormalities of erythrocyte membrane glycoconjugates that are most pronounced in type II CDA or hereditary erythroblastic multinuclearity with a positive acidified-serum test (HEMPAS). The abnormalities consist in hypoglycosylation of polylactoaminoglycans linked to proteins (as in band 3 glycoprotein) and ceramides (known under the name of polyglycosylceramides) as well as in accumulation of some oligoglycosylceramides: lactotriaosylceramide, neolactotetraosylceramide, and sometimes globotetraosylceramide. Glycophorin A is partially unglycosylated with respect to O-linked glycans. Types I and II of the disease are inherited in an autosomal recessive fashion. The aim of the present study was to investigate a possibility that heterozygosity with respect to CDAN2 gene in healthy carriers could be detected by analysis of erythrocyte membrane glycoconjugates. DESIGN AND METHODS: We examined a family which consisted of heterozygous parents and their two sons, one of whom was afflicted with CDA II (proband) while the other was healthy. In all family members the glycosylation status of band 3 glycoprotein, polyglycosylceramides and glycophorin A was evaluated from their carbohydrate molar composition. In addition we determined erythrocyte membrane contents of oligo- and polyglycosylceramides, and agglutinability of erythrocytes by anti-i antibody. RESULTS: We found that the heterozygous parents showed, but about 50% less pronounced, most of the typical abnormalities of erythrocyte membrane glycoconjugates that were present in the proband. These abnormalities included: hypoglycosylation of band 3, accumulation and hypoglycosylation of polyglycosylceramides, and accumulation of lactotriaosylceramide. The level of neolactotetraosylceramide in the erythrocyte membranes of the parents was, however, normal. Globotetraosylceramide content was elevated in erythrocytes from the proband and, surprisingly, even more so in the parents. Glycophorin A in the proband was only slightly abnormal. Erythrocytes from both the parents and the proband expressed increased agglutinability with anti-i antibody. All glycoconjugates examined were normal in erythrocytes from the healthy son. INTERPRETATION AND CONCLUSIONS: Individuals heterozygous with respect to CDAN2 gene can be identified through determination of the carbohydrate molar composition of band 3 and polyglycosylceramides as well as by an elevated erythrocyte content of polyglycosylceramides. In the parents these abnormalities show dosage effects. Determination of the carbohydrate molar composition of glycophorin A and of oligoglycosylceramides seems to be less promising. These findings indicate that the analysis of erythrocyte membrane glycoconjugates may be a valuable addition to the repertoire of methods used in studies on the genetics of CDA.

Adult↗
PubMed1991

[Key problems of antitumor immunity and glycoconjugates].

Two key problems of the antitumour immunity are considered: 1) very rapid changing of tumour-associated antigens; 2) tumour immunosuppression. Carbohydrate structures of the tumour-associated antigens (mainly glycoconjugates) are changing much more rapidly (hours, days) than the clones of antitumour T-killers proliferate. It is stated that the fundamental question of the nature of the glycoconjugate and endogenous lectin changing is not sufficiently studied. The endogenous lectins of the lymphocyte and macrophage surface are an old recognizing system responsible for a natural cell resistance to the tumour. Stimulation of this system by means of bacterial and syngeneic glycoconjugates is a promising direction in the tumour immunotherapy. Concerning the second aspect, the data are summarized according to which tumour cells produce inhibiting factors, including glycoconjugates, that suppress both proliferation and function of lymphocytes and macrophages. Developing the methods of rehabilitation of the immune system cells with the use of activating glycoconjugates and cytokines is the second important trend in the tumour immunotherapy.

Antigens, Neoplasm↗
PubMed1990

Use of lectins for detection of glycoconjugate changes in mucous epithelium of the chicken proventriculus.

The lectin binding pattern in the mucous epithelium of the chicken proventriculus was studied by using a peroxidase labeling method and correlated procedure. The nature of glycoconjugates in the mucous epithelium was found to change during the upward cell migration from deep to superficial parts. The superficial mucous epithelium (plica) was found to contain predominantly neutral glycoconjugates with N-acetyl-D-glucosamine residues and terminal galactose-N-acetylgalactosamine disaccharides whereas the deep epithelium (sulcus) contained acidic sulfated glycoconjugates with terminal sialic acid-galactose dimer. A continuous intraluminal mucous layer over the surface epithelium was found to contain a mixture of glycoconjugates secreted from both the plica and sulcus mucous cells. The data suggests that the changes in glycoconjugates of epithelial cells were closely correlated with cellular maturation.

Animals↗
PubMed1995

Histochemical study of glycoconjugates in the epididymis of the hamster (Mesocricetus auratus).

The glycoconjugates of hamster epididymis were investigated with conventional and lectin histochemistry. A zone of the caput epididymis, with particular histochemical characteristics, has been differentiated. beta-Elimination in combination with lectins was used to establish the presence and distribution of N- and O-linked glycoconjugates. The epithelium, spermatozoa and the intertubular matrix were rich in glycoconjugates. The Golgi apparatus and stereocilia of the principal cells were intensely positive with HPA, PNA and SBA lectins. beta-Elimination indicated that these cells contained abundant O-linked glycoconjugates. Apical and clear cells presented a common lectin affinity; their reactivities towards WGA and UEA-I were very positive. These cells probably contain abundant N-glycoconjugates. The spermatozoa were stained by periodic acid-Schiff (PAS) and by all the lectins (especially in the acrosome), except by those with an affinity for alpha-L-fucosyl residues; the most intense reaction was found with HPA, WGA, PNA and SBA. Changes in the sperm lectin binding along the ductus were observed: sperm flagellum abruptly acquired WGA and PNA labelling from the posterior caput, and HPA reactivity was negative only in the zone between the caput and the corpus.

Animals↗
PubMed1987

Histochemical evaluation of glycoconjugates in the male reproductive tract with lectin-horseradish peroxidase conjugates: I. Staining of principal cells and spermatozoa in the mouse.

Several glycoconjugates are thought to bind spermatozoa as they pass through reproductive ducts. Paraffin sections of testis, ductuli efferentes, epididymis, and vas deferens of male mice were stained with ten different lectin-horseradish peroxidase conjugates to localize possible sites of synthesis and secretion of such glycoconjugates, based on the carbohydrate moieties in their constituent oligosaccharide side chains. Principal (columnar) cells lining the efferent ducts, germinal epithelium, and developing and maturing spermatozoa were examined with light microscopy. Staining of the Golgi and apical zones of cells was interpreted as evidence for synthesis and secretion of glycoconjugates. Principal cells synthesized and secreted glycoconjugates with sugar moieties as follows: sialic acid, all regions of the efferent ducts examined; the terminal disaccharide D-galactose- (beta 1----3) -N-acetyl-D-galactosamine, all regions of ducts except epididymis I; terminal alpha-D-galactosamine, some cells in epididymis III-V; N-acetyl-D-galactosamine, ductuli efferentes, epididymis I, II, and some cells in epididymis III-V; alpha-L-fucose, ductuli efferentes, vas deferens, and all regions of the epididymis except IV; N-glycosidic side chains, ductuli efferentes, vas deferens, and epididymis I, IV, and V. All of these sugar residues as well as N-acetyl-D-glucosamine were associated with the acrosomes and tails of spermatozoa throughout the ducts except for alpha-N-acetyl-D-galactosamine in epididymis I, and all occurred during one or more stages of spermiogenesis. The synthesis and secretion of glycoconjugates that bind to spermatozoa appear to involve more regions of the primary reproductive structures than was believed previously.

Animals↗
PubMed1981

Isolation of a high molecular weight glycoconjugate derived from the surface of S purpuratus eggs that is implicated in sperm adhesion.

Sea urchin sperm-egg adhesion is mediated by bindin, a sperm surface protein that has lectin-like activity. Bindin agglutinates eggs, and this interaction has been shown to be inhibited by glycopeptides released from the egg surface by protease treatment. In this study, we report the purification and properties of such an egg surface glycoconjugate that may be involved in sperm adhesion. The glycoconjugate was partially purified by gel filtration and affinity chromatography on bindin particles. Upon gel filtration on Sepharose CL 4-B, the glycoconjugate elutes near the void volume, suggesting that it has a molecular weight in excess of one million. In addition, we have found that the egg surface glycoconjugate agglutinates bindin particles, indicating that it is multivalent. Carbohydrate analysis indicates that the glycoconjugate is composed primarily of fucose, xylose, galactose, and glucose. This purified egg surface component is the most potent inhibitor of bindin-mediated egg agglutination yet described.

Animals↗
PubMed1985

Lectin histochemistry of secretory and cell-surface glycoconjugates in the ovine submandibular gland.

Information about the chemical structure of ovine submandibular glycoconjugates was obtained in situ by means of a battery of peroxidase-conjugated lectins with affinity for specific terminal or internal sugars or sugar sequences in conjunction with neuraminidase digestion and periodate oxidation. Stored secretions in all mucous acinar cells contained disaccharide side chains consisting of N-acetylneuraminic acid linked to penultimate alpha-N-acetylgalactosamine localizing the predominant disaccharide demonstrated biochemically. A previously unrecognized disaccharide consisting of terminal N-acetylneuraminic acid and penultimate beta-galactose was found in 20-30% of mucous acinar cells. Occasional clusters of acini composed purely of serous cells contained an additional unrecognized glyco-conjugate with oligosaccharides terminated by sialic acid with O-acetylated polyhydroxyl side chains and penultimate beta-galactose. Serous demilunes, however, lacked detectable complex carbohydrate other than glycogen. Terminal sialic acid-beta-galactose dimers were present on the apical surface of all ducts except for intercalated ducts coated only with neutral glycoconjugate. Fucose assayed biochemically as a minor component occurred in abundance in glycoconjugates at the apical surface of all intercalated and most striated duct cells and within some striated duct cells. Terminal alpha-galactose not previously detected biochemically was localized at the apex of all duct cells. These results provide new knowledge concerning the structure of ovine submandibular glycoconjugates. They also illustrate the value of histochemical methods for elucidating the diversity of complex carbohydrates in an organ, locating different glycoconjugates in different types or subtypes of epithelial cells and demonstrating intracellular sites that contain complex carbohydrate.

Animals↗
PubMed1993

Enzymic determination of acidic glycoconjugates in human pancreatic juice.

Acidic glycoconjugates (glycosaminoglycans, sulfated glycopeptide, and sialoglycopeptide) were isolated by precipitation with cetylpyridinium chloride from human pancreatic juice after digestion with pronase. The acidic glycoconjugates were found exclusively in the proteinaceous precipitate that occurred during dialysis against a buffer of low ionic strength. The concentration of the acidic glycoconjugates in normal pancreatic juice was about 2.4 mg/L. The acidic glycoconjugates were characterized by electrophoresis on cellulose acetate membrane and chemical analysis before and after digestion with Streptomyces hyaluronidase, chondroitinase AC, chondroitinase ABC, and heparitinase. It was found that the major acidic glycoconjugates were heparan sulfate (39.3%), sulfated glycopeptide (34.4%), chondroitin sulfate (14.2%), and the minor ones hyaluronic acid (6.4%) and sialoglycopeptide (5.7%).

Chondroitinases and Chondroitin Lyases↗
PubMed1985

125I-glycoconjugate labels for identifying sites of protein catabolism in vivo: effect of structure and chemistry of coupling to protein on label entrapment in cells after protein degradation.

Residualizing radioactive labels are designed to remain entrapped within cells following degradation of a carrier protein, and have been used for identification of the tissue and cellular sites of plasma protein catabolism. In this study we describe a convenient synthesis and purification of a series of 125I-labeled glycoconjugates, and an evaluation of their efficiency of retention in liver following degradation of a model carrier protein, asialofetuin. Glycoconjugates were prepared in 65-90% yield by reductive amination of reducing sugars with aromatic amines using NaBH3CN. The products were purified in a single ion-exchange chromatographic step, and then labeled with 125I. The derivatives prepared were mono-and disubstituted lactitol-,cellobiitol-and glucitol-[125I]tyramine and lactitol-[125I]tyrosine. 125I-Glycoconjugates were coupled to asialofetuin using either cyanuric chloride or, for lactose-containing labels, by treatment with galactose oxidase followed by reductive amination with NaBH3CN. Attachment of labels by either procedure did not affect the normal rapid clearance of asialofetuin from the rat circulation nor its uptake and degradation in liver lysosomes. Leakage of 125I-labeled degradation products from cells was measured by following the kinetics of loss of whole-body radioactivity. We observed that degradation products from larger, disubstituted glycoconjugates were retained more efficiently than those from smaller and monosubstituted derivatives, and that glycoconjugates coupled to protein via reductive amination were retained in the body more efficiently than those coupled by cyanuric chloride. Overall, dilactitol-[125I]tyramine coupled to protein by reductive amination was entrapped most efficiently in liver.

Animals↗
PubMed1983

Membrane glycoconjugate visualization and biosynthesis in normal and retinoid-treated epidermis.

Cell-membrane glycoconjugates can be visualized for ultrastructural and fluorescence studies with certain surface markers, such as lectins and antisaccharide antibodies. When frozen sections of mammalian epidermis are treated with a battery of rhodamine-conjugated lectins, the cell membranes display a pattern of increased sugar complexity during keratinocyte maturation. Although this vectorial sequence is disrupted following retinoid treatment, these changes occur only at high doses and late in the course of treatment, suggesting that retinoid-induced alterations may be secondary. Seemingly as a result of specific glycosidase activity within the cytosol of both granular and cornified cells, lectin staining suddenly disappears from stratum corneum cell membranes. Although lectins stain membrane glycoconjugates of cultured human keratinocytes, quantitative techniques are required to recognize differences in proliferating versus postmitotic cells and in cultures supplemented with various growth factors. Whereas retinoids consistently depress glycoprotein synthesis in cultured keratinocytes, in organ culture they stimulate epidermal glycoprotein, and particularly glycolipid, biosynthesis. These studies suggest (1) that visualization of membrane glycoconjugates with lectins can reveal important variations in normal and pathologic epidermal differentiation, (2) that lectins may reveal subtle quantitative alterations in differentiation in vitro, (3) that retinoid stimulation of glycoconjugate biosynthesis either displays important species differences or requires a higher level of organization than occurs in cell culture, and (4) that the retinoid effect on glycoconjugate biosynthesis in organ culture may provide another useful bioassay for retinoid potency.

Animals↗
PubMed1984

The calcium dependency of mucus glycoconjugate secretion by canine tracheal explants.

Canine tracheal explants, incubated overnight with [14C]-glucosamine, elicited an enhanced secretion of ethanol-precipitated 14C-labelled glycoconjugate when challenged with methacholine, 10 microM. Explants were rendered deficient in total calcium content and unresponsive to methacholine, 10 microM, by incubating them in calcium-free medium for 18 to 22 h; however, the secretory response to the cholinergic agonist was restored with the addition of calcium to the medium. A dose-response relationship resulted when explants were challenged with methacholine in nutrient medium containing varied calcium concentrations (0.45 to 7.2 mM); alterations in the calcium concentration in the absence of methacholine had no significant effect on the basal secretion of 14C-labelled glycoconjugate. The calcium-selective ionophore A23187, 10 microM, stimulated [14C]-glycoconjugate secretion and induced the most significant effect in the presence of nutrient medium containing calcium. Verapamil, 10 microM, a calcium-entry blocker failed to inhibit basal or stimulated [14C]-glycoconjugate secretion; however, the intracellular calcium antagonist TMB-8, 10 to 100 microM, inhibited methacholine-induced [14C]-glycoconjugate secretion in a dose-dependent manner. These data suggest that respiratory mucus secretion is a calcium-dependent process and that intracellular calcium is more vital than extracellular calcium in supporting this phenomenon.

Animals↗