Differential distribution of sialic acid in exocrine pancreas and parotid gland

Flow cytometric measurements of intracellular Ca2+ mobilization in isolated rat pancreatic acinar cells after hormone stimulation and action of lectins

Isolated rat pancreatic acinar cells were loaded with the Ca(2+)-sensitive fluorescence dye Fluo 3 in vitro and the intracellular Ca2+ changes were analysed by flow cytometry. Morphology, viability, and loading with the dye were studied by light microscopy. Stimulation with cholecystokinin/pancreozymin (CCK) and its agonist caerulein as well as with carbamylcholine (Jestryl) led to an increase of intracellular calcium ions and a fluorescence peak. The slope and height of the Ca2+ signals were found to be influenced by preincubation of cells with some plant lectins (WGA, UEA, PHA, Con A, LCA, PNA). These effects are discussed with respect to the interaction of lectins with the carbohydrate chains of cell membrane receptors.

Fluorescence microscopic studies and flow cytometric measurements of lectin and hormone binding to isolated rat pancreatic acinar cells

The binding of fluorescence-labelled lectins and a fluorescence-marked hormone to the cell surface of isolated rat pancreatic acinar cells was studied by light microscopy and flow cytometric measurements. The pancreatic acinar cells were prepared by collagenase digestion. The fluorescence of cells was studied after binding of FITC-labelled WGA or UEA I as well as of FITC-marked pancreocymin/cholecystokinin (CCK-FITC) in a fluorescence microscope or FACScan. The strong binding of lectins was inhibited by preabsorption with the specific sugars. In comparison to the lectins the binding of CCK-FITC was low. There were two populations of acinar cells with different CCK-FITC binding capacity as detected by flow cytometry. The CCK-FITC cell surface fluorescence was significantly decreased by preincubation with unmarked hormone as well as with the non-labelled lectins. The inhibition of CCK-FITC binding by lectins is discussed in respect to a possible competition of the lectins and CCK for the CCK receptor.

Lectin binding studies with FITC-marked WGA and UEA I and flowcytometric measurements on isolated rat pancreatic acinar cells

Lectin binding to the glycocalyx of isolated rat pancreatic acinar cells was studied by flowcytometric measurements. The pancreatic exocrine cells were prepared after collagenase digestion and cleaned in a density gradient. The fluorescence of cells was measured in a FACScan after binding of FITC marked WGA or UEA I. The binding of lectins was inhibited by preabsorption of WGA-FITC with N-acetyl-glucosamine, sialic acid or chitinous and by preabsorption of UEA-FITC with alpha-L-fucose, respectively. Furthermore, we were able to measure a decreased WGA-FITC and UEA-FITC binding after a short preincubation of isolated cells with the peptide hormone cholecystokinin and its agonists (caerulein, pentagastrin).

Light and electron microscopic studies of lectin binding to the glycocalyx of rat pancreatic cells. II. Light microscopic changes after induction of an olive-oil pancreatitis

Using a battery of 7 horseradish peroxidase marked lectins (WGA, RCA I, PHA, LCA, PNA, UEA I, LPA) or 2 unmarked lectins (Con A, VAA I) and HRP-marked antibodies, the binding to acinar cells with a postembedding technique on semithin sections of rat pancreatic tissue after olive-oil pancreatitis was studied light microscopically. The lectin binding of the normal healthy rat pancreatic tissue (Jonas et al. 1991) changed remarkably. Whereas the apical glycocalyx of acinar cells with the strong binding of WGA, RCA I, and PHA remained unchanged within the first 10 min of damage, the basolateral cell surface lost the typical specific binding of UEA I within the initial phase of pancreatitis just 2 min after injection of olive-oil. Con A and VAA I were found to be very reactive with the necrotic cells 60 min after administration of oil. The results were discussed in relation to the possible functions of the 2 main domains of the pancreatic acinar cell glycocalyx.

Glycoconjugate composition of mammalian parotid glands elucidated in situ by lectins and glycosidases

Sugar specific lectins (PNA, RCA I, LPA, SBA, DBA, GSA IB4, GSA II, WGA, LTA, UEA I, Con A, LCA) with and without prior selective glycosidase digestion (sialidase, alpha-fucosidase, alpha-mannosidase, beta-N-acetylglucosaminidase, alpha- and beta-galactosidase, beta-glucosidase) were used in order to investigate the distribution of native accessible carbohydrates and obtain information dealing with the composition of terminal disaccharides within glycoconjugates present in acinar compartments and ductal segments of mammalian (mouse, rat, hare, and rabbit) parotid glands. Glycoconjugates containing variable amounts of mannose, glucose, N-acetylgalactosamine and N-acetylglucosamine were present in the parotid glands of all species. However, these carbohydrate chains exhibited a different composition of terminal sequences within each type of gland. For example, sialylated components having the terminal dimers sialic acid-galactose and sialic acid-N-acetylgalactosamine were found in all acinar cells, whereas fucoglycoconjugates with terminal disaccharide fucose-galactose were localized in the rat striated ducts and hare acinar cells. The terminal sequence alpha-galactose-beta-galactose was demonstrated in the mouse acinar cells. Finally, glycoconjugates characterized by the terminal dimer beta-galactose-N-acetylgalactosamine were demonstrated in the mouse acinar and ductal cells and the rat ductal ones. Thus, present findings outlined and further confirmed the possibility to elucidate the oligosaccharide structure in situ using lectin histochemistry combined with enzymatic degradation.

Light and electron microscopic studies of lectin binding on the glycocalyx of rat pancreatic cells. I. Normal tissue and isolated cells

Lectin binding of the glycocalyx of pancreatic tissue sections as well as of isolated pancreatic acini and acinar cells was studied of healthy wistar rats by light and electron microscopy. For light microscopy, we used FITC (WGA, RCAI, LCA) or peroxidase marked (WGA, RCAI, PNA, PHA, LCA, UEAI, LPA) as well as unmarked lectins (Con A, VAA I). Gold marked lectins were used for electron microscopy (WGA, RCAI, LCA, HPA, PNA, VAAI-B). Intact acinar cells in pancreatic tissue sections and isolated acini showed a strong binding of WGA, RACI, and HPA on the apical cell surface, whereas VAAI, UEAI, LCA, and Con A reacted strongly with the basolateral glycocalyx, but not with the apical surface. The 2 main domains of the glycocalyx of pancreatic cells showed their specific lectin binding so long as the junctional complexes between the cells are intact. The polarity of the cell surface of pancreatic acinar cells is discussed in regard to the possible function of the 2 domains.

Dipeptidyl peptidase (DPP) IV in rat organs. Comparison of immunohistochemistry and activity histochemistry

Immunohistochemistry and activity histochemistry were used to study the localization of dipeptidyl peptidase (DPP) IV in rats. For immunohistochemistry, polyclonal as well as monoclonal anti-DPP IV antibodies were employed. The pattern of DPP IV immunoreactivity, determined with polyclonal anti-DPP IV antibody, corresponds to the histochemical pattern found for the enzymic activity of DPP IV. Immunoreactivity was present, in addition, in nerve cells, lateral membranes of certain surface epithelia, e.g., Fallopian tube, uterus and vesicular gland, in the luminal cytoplasm of e.g., vesicular gland epithelium, and in mucous cells of Brunner's gland. The monoclonal antibodies against DPP IV recognized four different epitopes (A-D) of the DPP IV molecule, and revealed that certain epitopes were not detectable by immunohistochemistry in some organs. Generally, the staining intensities for epitopes A, B, C and D decreased in that order. Usually, the monoclonal antibodies against epitopes A and B showed similar reaction patterns to those as obtained with the polyclonal antibody. Epitope D was recognized in the lumen of the duct system of exocrine glands and the intestine. Furthermore, high reactivity of this epitope was detected in goblet cells of the intestine, where no DPP IV activity was present.

Lectin binding on carbohydrate compounds of the flask cells in the claw-frog kidney

The carbohydrate compounds of the mucus of flask cells in the kidney of claw-frogs (Xenopus laevis) were analysed through lectin binding studies. After removing epoxy resin semithin sections were incubated with 7 lectins (WGA, RCA I, PNA, LCH, UEA, LPA) marked by horseradish peroxidase and 2 unmarked lectins (VAA, Con A). The glycosaminoglycans in the canalicular lumen of flask cells showed a strong reaction with WGA and RCA, whereas the binding of PHA, Con A, and LCH was weaker. No reaction was observed with PNA, UEA, LPA, and VAA. The mucus of the flask cells seems to be rich in N-acetyl-glycosamine and -galactosamine. It contains also mannose, glucose, and galactose, but seems to have no fucose or N-acetyl-sialic acid residues.