Macromolecular properties and end-group analysis of heparin isolated from bovine liver capsule

Size-exclusion chromatography of heparin oligosaccharides at high and low pressure

Recent findings on specific and non-specific interactions of glycosaminoglycans (GAGs) accentuate their pivotal role in biology and the call for improved sequencing tools. The present study evaluates size-exclusion chromatography (SEC) of heparin oligosaccharides at high and low pressure, requiring amounts as low as 0.2 microgram, using conventional UV detection after depolymerization with heparin lyases. Because of their high charge at physiological pH, SEC elution volumes of heparin oligosaccharides depend on both molecular size and charge repulsion from the matrix. As a consequence, SEC elution volumes of GAGs are smaller than those of globular proteins of similar molecular weight, and this might be exploited. Accordingly, larger heparin oligosaccharides are best separated according to their size at high ionic strength of the mobile phase (>30 mM); in contrast, disaccharides are best separated according to their charge at low ionic strength, compatible with on-line coupling to mass spectrometry. Optimized SEC affords separation of characteristic heparin trisaccharides that contain uronic acid at the reducing end and suggest cellular storage of heparin as a free glycan.

Glycosaminoglycans in rat mucosal mast cells

Rats were infected with the nematode Nippostrongylus brasiliensis, resulting in an approx. 5-fold increase in the number of mucosal mast cells and the histamine content of the intestinal (jejunum) wall. After injection of the infected animals with inorganic [35S]sulphate, a similar increase in the yield of labelled intestinal glycosaminoglycans was observed, compared with uninfected control rats. Autoradiography showed a highly selective labelling of the numerous mucosal mast cells and of the few connective-tissue mast cells in the subserosal region of the bowel. Analysis of the labelled polysaccharide from the infected animals showed that almost 60% of this material consisted of oversulphated galactosaminoglycan, whereas heparin-related polysaccharides accounted for only 13%. The galactosaminoglycan contained 4-monosulphated and 4,6-disulphated N-acetylgalactosamine residues in approx. 5:1 molar ratio, both being linked to D-glucuronic acid residues; the occurrence of L-iduronic acid units could not be excluded. No significant difference in structure was found between this polysaccharide and the corresponding component isolated from uninfected rats. It is concluded that the major polysaccharide produced by rat mucosal mast cells in vivo is an oversulphated galactosaminoglycan rather than heparin.

Interaction of lipoprotein lipase with native and modified heparin-like polysaccharides

1. Lipoprotein lipase (EC 3.1.1.34), which was previously shown to bind to immobilized heparin, was now found to bind also to heparan sulphate and dermatan sulphate and to some extent to chondroitin sulphate. 2. The relative binding affinities were compared by determining (a) the concentration of NaCl required to release the enzyme from polysaccharide-substituted Sepharose; (b) the concentration of free polysaccharides required to displace the enzyme from immobilized polysaccharides; and (c) the total amounts of enzyme bound after saturation of immobilized polysaccharides. By each of these criteria heparin bound the enzyme most efficiently, followed by heparan sulphate and dermatan sulphate, which were more efficient than chondroitin sulphate. 3. Heparin fractions with high and low affinity for antithrombin, respectively, did not differ with regard to affinity for lipoprotein lipase. 4. Partially N-desulphated heparin (40-50% of N-unsubstituted glucosamine residues) was unable to displace lipoprotein lipase from immobilized heparin. This ability was restored by re-N-sulphation or by N-acetylation; the N-acetylated product was essentially devoid of anticoagulant activity. 5. Partial depolymerization of heparin led to a decrease in ability to displace lipoprotein lipase from heparin-Sepharose; however, even fragments of less than decasaccharide size showed definite enzyme-releasing activity. 6. Studies with hepatic lipase (purified from rat post-heparin plasma) gave results similar to those obtained with milk lipoprotein lipase. However, the interaction between the hepatic lipase and the glycosaminoglycans was weaker and was abolished at lower concentrations of NaCl. 7. The ability of the polysaccharides to release lipoprotein lipase to the circulating blood after intravenous injection into rats essentially conformed to their affinity for the enzyme as evaluated by the experiments in vitro.

Uptake and degradation of mast-cell granules by mouse peritoneal macrophages

35S-labelled mast-cell granules isolated from mouse mastocytomas were added to mouse macrophages in vitro. The granules were avidly phagocytosed, and subsequently the radioactivity was released to the medium as inorganic [35S]sulphate. After pulse-labelling, a total of about 80% of the cell-associated radioactivity was thus released in the course of 24 h, indicating an extensive breakdown of the sulphated polysaccharides, mainly heparin, present in the granules. The uptake of the mast-cell granules caused pronounced, but reversible, spreading of the macrophages.

Articular cartilage, blood serum glycosaminoglycans and glycoproteins in osteoarthritis deformans

Glycosaminoglycans in articular cartilage from human femoral heads have been isolated and fractionated by means of a cellulose microscale technique. The glucosaminoglycans have been identified by different procedures as keratan sulphate, hyaluronic acid, heparitin sulphate, chondroitin 4-sulphate, chondroitin 6-sulphate and dermatan sulphate. Osteoarthritic cartilage showed a significant reduction of dermatan sulphate, chondroitin 6-sulphate, keratan sulphate and heparitin sulphate. The content of glycoprotein carbohydrate components in the cartilage (neuraminic acid derivatives, hexoses, 6-deoxyhexoses) also appeared to be reduced. It has been shown that chondroitin 4-sulphate, keratan sulphate and dermatan sulphate content was considerably increased in osteoarthritic serum. Among serum glycoprotein carbohydrate constituents only the content of 6-deoxyhexoses was slightly increased.

Modulation of adenylate cyclase activity by sulfated glycosaminoglycans. II. Effects of mucopolysaccharides and dextran sulfate on the activity of adenylate cyclase derived from various tissues

Heparin was found to be the most potent inhibitor of rat ovarian luteinizing hormone-sensitive adenylate cyclase (I50 = 2 microgram/ml) when compared to other naturally occurring glycosamin oglycans. This inhibition was also apparent when this enzyme was stimulated by follicle-stimulating hormone or prostaglandin E2. Heparin was also found to inhibit glucagon-sensitive rat hepatic adenylate cyclase, and the prostaglandin E1-sensitive enzyme from rat ileum and human platelets. In contrast, heparin stimulated the dopamine sensitive adenylate cyclase from rat caudate nucleus. The sulfated polysugar dextran sulfate exerts similar effects on adenylate cyclase activity of the rat ovary and was shown to inhibit hormone binding to rat ovarian plasma membrane in a manner similar to that exerted by heparin. In contrast to heparin, dextran sulfate inhibited dopamine-sensitive adenylate cyclase from rat caudate nucleus.

Structure-function relationships of heparin species

We have fractionated porcine heparin species of low molecular weight, with an average specific anticoagulant activity of 96 units/mg by affinity chromotography. Highly active and relatively inactive preparations of similar size were obtained with specific anticoagulant activities of 360 and 4 units/mg, respectively. The highly active heparin fraction possesses 1.1 additional residues of glucuronic acid and 1.5 fewer residues of N-sulfated glucosamine per molecule compared to the relatively inactive species. This decrease in N-sulfated glucosamine appears to be secondary to a corresponding increase in N-acetylated glucosamine. This form also contains a tetrasaccharide sequence with a N-sulfated glucosamine at its reducing end as well as equivalent amounts of glucuronic acid and iduronic acid. Furthermore, the internal glucosamine residue of this sequence appears to be N-acetylated. Sufficient amounts of this tetrasaccharide sequence are present within the highly active preparation such that each molecule may be endowed with this structure. The relatively inactive product contains a significantly decreased quantity of this tetrasaccharide sequence such that only [unk]20% of these molecules may possess this structure. The mean distance between nonsulfated uronic acid residues of the highly active species is smaller than that separating similar residues of the relatively inactive product. In addition, a larger number of the nonsulfated uronic acid residues of the highly active material appears either to be present in a restricted region of the molecule separated only by glucosamine residues or to be located at penultimate positions within the polysaccharide chain.

Cytochemical variation of mast cells in the skin of the rat

The mast cells of the skin of the external ear of the rat have been examined, with a view to the possible identification of different cell-types. It was not possible to discern more than one type of cell using criteria of size, shape, nuclear chromophilia or sizes of granules. The cytoplasmic granules of all of the cutaneous mast cells were tingible with Alcian blue (pH. 1.0 and 2.5) and, metachromatically, with toluidine blue 0. These properties were attributable to the heparin contained in the granules. The cells all gave positive reactions with the diazosafranine method, possibly by virtue of their content of serotonin. About two thirds of the mast cells in the dermis contained granules which were stainable by the periodic acid-Schiff (PAS) method and which could bind concanavalin A. It is suggested that these latter cells contain, in addition to heparin, a neutral mucosubstance characterized by a high content of alpha-d-glucosyl and/or alpha-d-mannosyl monosaccharide residues. The PAS-positive cells were relatively more abundant in vascular adventitiae and nerves and less so in the general connective tissue of the dermis than were the mast cells which did not contain the second mucosubstance.

Metabolism of macromolecular heparin in mouse neoplastic mast cells

1. Polysaccharide in a heparin-producing mouse mastocytoma was pulse-labelled in vivo with [35S] sulphate, and after various periods of time was isolated from subcellular fractions. Such fractions were recovered from tissue homogenates by consecutive centrifugations at 1000g for 10min, 20000g for 20min and 100000g for 1h. Initially the 35S-labelled polysaccharide formed occurred principally in the second centrifugal fraction (20000g precipitate), with small amounts in the first (granular) and third (microsomal) fractions. Analysis for glycosyltransferase activity confirmed that glycosaminoglycans were formed chiefly in particles sedimenting at 20000g. Molecules of this newly synthesized polysaccharide were considerably larger than those of commercially available heparin, as judged from gel chromatography. 2. Within the first hour after injection of [35S]sulphate, most of the labelled polysaccharide was redistributed from the second to the first centrifugal fraction. During, and possibly also after, this shift, the macromolecular polysaccharide was degraded, ultimately to the size of commercial heparin. The degradation process appeared complete 6h after injection of [35S]sulphate. 3. Particulate subcellular fractions were incubated with macromolecular [35S]heparin and the products were analysed by gel chromatography. Significant degradation of the substrate occurred only with the second centrifugal fraction. Further characterization of this fraction, by density-gradient centrifugation in iso-osmotic colloidal silica, revealed a single visible band of particles, at approximately the same density at lysosomes. This band contained all the beta-glucuronidase, 35S-labelled endogenous polysacchride and heparin-degrading enzyme present in the second fraction.