Biomedical subjects

W Reutter

Publications and source records attributed to W Reutter.

At least 127 records · Page 7Linked to original sources

PubMed1990

Calcium-binding proteins 33 kDa, 35 kDa, and 65/67 kDa in normal rat and Morris hepatoma tissues. A biochemical and immunohistochemical study.

Polyclonal antibodies were raised against membrane-associated calcium-binding proteins (apparent molecular masses 65000 and 67000 (CBP 65/67) and 33000 and 35000 (CBP 33 and CBP 35)), which were isolated from rat liver and Morris hepatoma. Using immunoblotting, various amounts of CBP 33 and CBP 35 as well as CBP 65/67 were detected in most rat organs. Using alkaline phosphatase and monoclonal-anti-alkaline phosphatase antibodies (APAAP), all the calcium-binding proteins were detected by immunohistochemical techniques in the plasma membranes of many cells, such as vascular endothelial cells, lymphocytes, epididymal principal cells, secretory and excretory duct cells of certain exocrine glands, straight distal tubular cells of the kidney, and in the cytoplasm of muscle cells and fibres as well as nerve cells and chondrocytes, and in connective tissue elements. Immunohistochemical analysis also showed that in polarized epithelial cells, e.g., renal tubular cells, epididymal principal cells or excretory duct cells, these calcium-binding proteins are present exclusively or mostly in the luminal plasma membrane.

Animals↗

PubMed1990

Comparative immunohistochemistry and histochemistry of dipeptidyl peptidase IV in rat organs during development.

The occurrence of dipeptidyl peptidase (DPP) IV during development in Wistar rat organs was studied on day 10, 16 and 21 of gestation and on day 1, 4, 8, 13, 21, 26 and 60 after birth comparing immunohistochemistry and activity histochemistry. A polyclonal antibody, as well as monoclonal antibodies recognizing four different epitopes (A-D) of the DPP IV molecule, were employed for the immunohistochemical studies. In all investigated tissues, immunoreactivity with the polyclonal antibody appeared earlier than DPP IV activity and was already present on day 10 of gestation in the plasma membranes of embryonic and extraembryonic (decidual) cells. At these and other sites, e.g. brain capillary endothelium and tracheal or bronchial epithelium, immunoreactivity with the polyclonal antibody decreased or disappeared after birth and enzyme activity never developed. Immunoreactivity with the monoclonal antibodies appeared later than that with the polyclonal antibody, and mostly in those structures where DPP IV activity was subsequently found. The monoclonal antibody against epitope D showed a high reactivity in the epididymal duct, renal collecting ducts and in all domains of the hepatocyte plasma membrane, where neither DPP IV activity nor immunoreactivity with the other antibodies were observed. Our results also suggest that DPP IV might be present as a molecule before it becomes catalytically active and that immunoreactivity occurs at more sites than DPP IV activity. However, it cannot be excluded that the polyclonal antibody and the monoclonal antibody against the epitope D cross-react with as yet uncharacterized proteins, which express common epitopes during embryonic development, but are not present in the tissues of adult Wistar rats.

Aging↗

PubMed1990

Optimized deglycosylation of glycoproteins by peptide-N4-(N-acetyl-beta-glucosaminyl)-asparagine amidase from Flavobacterium meningosepticum.

Peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F(PNGase F) from Flavobacterium meningosepticum is a highly useful enzyme for the structural analysis of N (asparagine)-linked carbohydrate chains derived from glycoproteins. The enzyme was enriched using a published procedure [Tarentino AL, Gomez CM, Plummer TH, Jr (1984) Biochemistry 1985:4665-71; Tarentino AL, Plummer TH, Jr (1987) Methods Enzymol 138:770-78] and further purified by hydrophobic interaction HPLC on a weak hydrophobic TSK-Ether column from which it was eluted by a decreasing gradient of 1.7 M ammonium sulphate in 100 mM sodium phosphate, pH 7.0, containing 5 mM EDTA. To determine the optimal conditions for a complete deglycosylation of glycoproteins by PNGase F, experiments were performed with human alpha 1-acid glycoprotein, because the five complex type carbohydrate chains are quite resistant to enzymic hydrolysis. The influence of different detergents on the enzyme reaction was studied. Complete deglycosylation of human alpha 1-acid glycoprotein was achieved by the use of 60 mU/ml PNGase F in 0.25 M sodium phosphate buffer, pH 8.6, containing 0.2% (w/v) SDS, 20 mM mercaptoethanol and 0.5% Mega-10.

Amidohydrolases↗

PubMed1990

Enkephalin affects ion transport via the enteric nervous system in guinea-pig ileum.

The endogenous opioid enkephalin drives ion transport towards absorption. To determine the site and mechanism of this effect, fractionated stripping of guinea-pig ileum was carried out. The muscularis propria, including myenteric plexus, was removed by partial stripping. The submucosa, including the submucosal plexus, plus the muscularis mucosae were removed by total stripping. For binding studies, epithelial cells were removed by the method of Weiser leaving the lamina propria mucosae with the mucosal plexus. Radio-receptor-assay with (3H)2-D-ala-5-D-leu-enkephalin revealed enkephalin binding sites in the submucosa plus muscularis mucosae (KD = 3.6 nmol l-1; Vmax = 7.3 fmol mg-1) and in the lamina propria mucosae (KD = 4.2 nmol l-1; Vmax = 5.1 fmol mg-1. The binding was stereospecific in both layers. No binding was detected on epithelial cells. In the Ussing chamber, partially stripped ileum exhibited spontaneous ISC which was abolished by addition of tetrodotoxin (TTX) or by total stripping indicating that this ISC was neuronally stimulated by the submucosal plexus. Electrogenic chloride secretion was identified as contributing to this ISC, since the TTX-sensitive part of ISC in the partially stripped ileum was lacking in Cl- and HCO3-free medium, reappeared after addition of Cl consistent with Michaelis-Menten kinetics (Km = 19 nmol l-1) and was reversed by serosal addition of bumetanide. In addition, enkephalin increased electroneutral NaCl-absorption as obtained by Na- and Cl-flux measurements. Enkephalin decreased this spontaneous neuronally stimulated electrogenic Cl-secretion in the partially stripped ileum, but had no effect in totally stripped ileum if ISC was stimulated at the cellular level by theophylline or PGE1. We conclude that ganglia located in the submucosal plexus regulate intestinal ion transport. Enkephalin acts by presynaptic inhibition via receptors on these neurons in the submucosa and/or via receptors on their neurites in the lamina propria mucosae.

Animals↗

PubMed1990

Nutritionally-induced elevation of serum proteinase inhibitors and reduced 3-methylhistidine excretion in the rat.

One group of growing rats was fed ad libitum a low protein and energy diet (PER). A second group was fed a low protein diet (PR). Both these groups showed a gain in weight below that of the control group. A third group was fed a very low protein and energy diet (VPER). A weight gain could also be observed in this group but this gain was lower than those observed in the first two groups. A fourth group that was on a very low protein diet (VPR) gained almost no weight. After 6 weeks a significant reduction in 3-methylhistidine excretion in urine was observed in all the experimental animals with lowest values found in the VPER and VPR groups. Total serum protein levels declined to a certain extent because of the protein and energy restrictions but albumin and transferrin remained largely unaffected. Significantly lower serum concentrations were found only in the VPR group. The rat serum proteinase inhibitors alpha 1-macroglobulin and alpha 1-inhibitor3 decreased when protein and energy were restricted and alpha 1-proteinase inhibitor decreased only in the VPER and VPR groups. alpha 2-macroglobulin and alpha 1-cysteine proteinase inhibitor concentrations increased considerably in the serum of the experimental groups. The results are discussed in relation to the probable role of the latter two inhibitors in the adaptation process when protein and energy were restricted and compared to similar observations recorded in man.

Animals↗

PubMed1990

Glycoproteins of rat liver plasma membranes: their hepatocellular, intestinal and renal expression in rat, rabbit and human.

Expression of six glycoproteins (Mr = 60,000 (gp 60), 80,000 (gp 80), 110,000 (gp 110), 120,000 (gp 120), 140,000 (gp 140), 160,000 (gp 160)) recently purified from rat liver plasma membranes (LPM) were compared in the liver, small intestine and kidney of the rat, rabbit and human. Immunoblotting studies with monospecific antisera showed that five of the six glycoproteins (gp 60, gp 80, gp 110, gp 120, and gp 140) were expressed not only in LPM of the rat but also in LPM from the rabbit and human with Mr corresponding to those of the glycoproteins isolated from the rat. In contrast, the glycoprotein gp 160 was only detected in rat liver. The same pattern of expression was found by immunofluorescence on isolated hepatocytes from the three species. In rat liver, the glycoproteins were localized primarily either in the bile canalicular domain (gp 80, gp 110, gp 120), or in the sinusoidal domain (gp 60, gp 140), or they were distributed over the whole hepatocellular surface (gp 160). In rat, but not in rabbit or human, the glycoproteins gp 110, gp 120 and gp 140 were also found in the small intestine localized either in the brush border membrane (gp 110, gp 120) or over the whole surface membrane of enterocytes (gp 140). Gp 120 was also detected in the luminal pole of tubular epithelial cells of rats kidney. The data show that LPM of different mammalian species share several common glycoprotein antigens. These glycoproteins, that are also partly expressed in extrahepatic tissues, may represent plasma membrane structures conserved among mammalian species.

Animals↗

PubMed1989

Preparative isolation of glycoproteins from plasma membranes of different rat organs.

By a combination of high-performance affinity chromatographic (HPAC) methods, several membrane proteins from liver, Morris hepatoma and kidney were isolated. The use of a tandem system, consisting of a concanavalin A (ConA) and a wheat germ agglutinin (WGA) high-performance liquid chromatographic (HPLC) column, as a first purification step allowed the isolation of proteins directly from organ homogenates. In a subsequent step, the membrane proteins can be isolated by simply using a combination of immunoaffinity HPLC and preparative sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). However, with these methods most proteins lose their biological activity. If native proteins are required, a combination of different HPAC methods has to be applied. Several membrane proteins were isolated in milligram amounts under non-denaturing conditions using either HPAC columns or Mem Sep membranes with immobilized lectins, collagen, amino acids, crown ethers or heparin.

Animals↗

PubMed1989

Rapid intramolecular turnover of N-linked glycans in plasma membrane glycoproteins. Extension of intramolecular turnover to the core sugars in plasma membrane glycoproteins of hepatoma.

Plasma membrane glycoproteins of rat hepatocytes undergo a rapid terminal deglycosylation in that the terminal sugars of the oligosaccharide side chains are rapidly removed from the otherwise intact glycoproteins [Tauber, R., Park, C.S. & Reutter, W. (1983) Proc. Natl Acad. Sci. USA 80, 4026-4029]. The present paper demonstrates that this rapid intramolecular turnover of plasma membrane glycoproteins is not restricted to peripheral sugars but, in contrast to liver, in hepatoma the core sugars of the oligosaccharide chains are also involved. Intramolecular turnover was measured in Morris hepatoma 7777 in five plasma membrane glycoproteins with Mr of 85,000 (hgp85), 105,000 (hgp105), 115,000 (hgp115), 125,000 (hgp125), 175,000 (hgp175) (hgp = hepatoma glycoprotein) that were isolated and purified to homogeneity by concanavalin-A--Sepharose affinity chromatography and semipreparative SDS gel electrophoresis. Analysis of the carbohydrates of hgp85, hgp105, hgp115 and hgp125 revealed the presence of N-linked oligosaccharides containing L-fucose, D-galactose, D-mannose and N-acetyl-D-glucosamine, but only of trace amounts of N-acetyl-D-galactosamine; hgp175 additionally contained significant amounts of N-acetyl-D-galactosamine, indicating the presence of both N- and O-linked oligosaccharides. As shown by digestion with endoglucosaminidase H, the N-linked oligosaccharides of hgp105, hgp115, hgp125 and hgp175 were of the complex type, whereas hgp85 also contained oligosaccharides of the high-mannose type. Half-lives of the turnover of the oligosacharide chains and of the protein backbone of the five glycoproteins were measured in the plasma membrane in pulse-chase experiments in vivo, using L-[3H]fucose as a marker of terminal sugars, D-[3H]mannose as marker of a core sugar and L-[3H]leucine for labelling the protein backbone. Protein backbones of the five glycoproteins were degraded with individual half-lives ranging over 41-90 h with a mean of 66 h. Compared to the degradation of the polypeptide backbone, both the terminal sugar L-fucose and the core sugar D-mannose turned over with much shorter half-lives averaging about 20 h in the five glycoproteins. The data show that, conversely to liver, within plasma membrane glycoproteins of hepatoma not only peripheral sugars but also core sugars of the oligosaccharides are split off during the life-span of the protein backbone. It may therefore be assumed that this reprocessing of plasma membrane glycoproteins is sensitive to malignant transformation.

Animals↗

PubMed1989

Crown ethers as ligands for high-performance liquid chromatography of proteins and nucleic acids.

By immobilization of the crown ether 1,10-diaza-18-crown-6 to different porous and non-porous, epoxy-activated supports, a chromatographic sorbent was prepared, which, mediated by potassium ions, can be used for the separation of both nucleic acids and proteins. Model experiments have been carried out with ribonucleic and deoxyribonucleic acids. In experiments with standard proteins the influence of pH and the role of loading of the column with potassium ions were demonstrated. The column was used for separating complex protein mixtures, such as serum and plasma membrane extracts, in the presence of detergents.

Chromatography, High Pressure Liquid↗

PubMed1989

Localization of a putative cell adhesion molecule (gp110) in Wistar and Fischer rat tissues.

A plasma membrane glycoprotein (gp110) involved in cellular adhesion was studied in Wistar and Fischer rats. For quantitative analysis of the gp110 molecule a sandwich-ELISA was used. High quantities of gp110 were found especially in the liver, small intestine, submandibular gland and lung. The distribution and localization of the gp110 were investigated by immunohistochemistry utilizing soluble complexes of alkaline phosphatase and monoclonal anti-alkaline phosphatase antibodies. Immunoreactivity was present in plasma membranes of vascular endothelial cells of some organs. Furthermore, immunostaining also occurred in plasma membranes of lymphocytes, exocrine gland cells, excretory duct cells, hepatocytes, epithelial cells of the small intestine, kidney and vesicular gland and in the cytoplasm of renal connecting and collecting duct cells. The localization of gp110 in the luminal domain of the plasma membrane at many sites suggests that this glycoprotein is also involved in processes distinct from cell adhesion.

Animals↗

PubMed1989

Biochemical properties of dipeptidyl peptidase IV in liver and hepatoma plasma membranes.

In the present investigation we compared the glycoprotein DPP IV from rat liver and Morris hepatoma 7777 by means of biochemical and immunological methods. For that purpose nine monoclonal anti-DPP IV-antibodies recognizing four different epitopes and a monospecific anti-DPP IV-antiserum were applied. In the homogenates of both tissues a plasma membrane-bound and a soluble form were detected. The immunological cross-reactivity of both forms was demonstrated with the antiserum and the monoclonal antibodies against the epitopes A, B and C while epitope D was restricted to liver plasma membrane. Differences of the distinct DPP IV forms were exhibited in the molecular weights, isoelectric points and peptide maps. In the hepatoma homogenate only 10% of DPP IV activity was found compared to normal liver but the ratio of soluble to membrane-bound form is higher in the hepatoma than in the liver. The fractionation of the homogenates into different cell components revealed for the liver a continuous increase of DPP IV activity from the endoplasmic reticulum fractions to the Golgi apparatus and finally to the plasma membranes. By contrast, in hepatoma the flow from the Golgi apparatus to plasma membrane was greatly reduced. The loss of DPP IV from the surface of cultured hepatoma cells was concomitant with a decrease of cell-substratum adhesion. DPP IV was found to be inserted into the liver plasma membrane by two different mechanisms, a phospholipase C-sensitive and a papain-sensitive one. In the hepatoma the phospholipase C-sensitive anchorage was not expressed. Besides liver and hepatoma the distribution of DPP IV was characterized in various rat organs by enzyme activity, histochemistry and immunohistochemistry with the anti-DPP IV-antibodies.

Animals↗

PubMed1989

Decreased intramolecular turnover of L-fucose in membrane glycoproteins of rat liver during liver regeneration.

In plasma membrane glycoproteins of rat liver L-fucose undergoes a rapid intramolecular turnover in that fucose residues are removed from the glycoproteins (Tauber, R., Park, C.S. & Reutter, W. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 4026-4029). The present paper demonstrates that the intramolecular turnover of L-fucose is markedly decreased during liver regeneration. Turnover half-lives of L-fucose were measured in regenerating liver by pulse-chase experiments in five plasma membrane glycoproteins (Mr 60,000 (gp60), 80,000 (gp80), 120,000 (gp120), 140,000 (gp140), and 160,000 (gp160). The glycoproteins were isolated from plasma membranes by concanavalin A-Sepharose affinity chromatography and semipreparative NaDodSO4 polyacrylamide gel electrophoresis. L-Fucose turned over in the five glycoproteins with heterogeneous half-lives ranging from 22 h (gp160) to 49 h (gp120). The protein moieties of the glycoproteins were degraded with half-lives ranging from 56 h (gp80) to 107 h (gp140). Relative to the half-life of the protein backbone the half-live of L-fucose was increased in the five membrane glycoproteins by 70% (gp60), 150% (gp80), 182% (gp120), 60% (gp140) and 16% (gp160) during liver regeneration when compared to normal liver. The data show that L-fucose turns over in different membrane glycoproteins with individual rates, and that loss of L-fucose from plasma membrane glycoproteins is reduced in rapidly proliferating liver after partial hepatectomy.

Animals↗

PubMed1989

Selective isolation of individual cell surface proteins from tissue culture cells by a cleavable biotin label.

A method was developed to isolate cell surface proteins by a simple two-step procedure. Hepatocyte cell surface proteins were labeled by a cleavable biotin derivative in a covalent pulse reaction. Under the described conditions, NHS-SS-biotin proved to be an impermeant, cell surface-specific label which does not affect the impermeant, cell surface-specific label which does not affect the viability of rat hepatocytes. Biotinylated cell surface proteins could be selectively separated under non-denaturing conditions from non-biotinylated proteins and biotin-containing carboxylases by avidin affinity chromatography and sulfhydryl-mediated elution. Subsequent to alkylation of the eluted protein, individual cell surface proteins could be isolated by immunoprecipitation as shown for a selected Mr 120,000 glycoprotein gp120 of the hepatocyte plasma membrane. Using this technique, a transit time of gp120 from the endoplasmic reticulum to the cell surface of 2 h was determined. The results show that the combination of labeling with a cleavable biotin derivative, non-denaturing avidin affinity chromatography and immunoprecipitation is a useful method to isolate and study individual cell surface proteins.

Alkylation↗

PubMed1988

Remodeling of a rat hepatocyte plasma membrane glycoprotein. De- and reglycosylation of dipeptidyl peptidase IV.

The present paper demonstrates the terminal de- and reglycosylation of a rat hepatocyte plasma membrane glycoprotein, dipeptidyl peptidase IV (DPP IV). Cultured hepatocytes were used in pulse-chase experiments with [3H]L-fucose and [14C]N-acetyl-D-mannosamine as markers for terminal carbohydrates, [3H]D-mannose as marker of a core-sugar, and [35S]L-methionine for labeling the protein backbone. Membrane DPP IV was immunoprecipitated with a polyclonal antibody which bound selectively at 4 degrees C to the cell-surface glycoprotein. The times of maximal labeling of hepatocyte plasma membrane DPP IV were 6-9 min for [3H]L-fucose, 20 min for [3H]D-mannose, and 25 min for [35S]L-methionine. When antibodies were bound to cell-surface DPP IV at 4 degrees C, the immune complex remained stable for more than 1 h after rewarming to 37 degrees C, despite ongoing metabolic and membrane transport processes. This was shown by pulse labeling with [35S]L-methionine at 37 degrees C, followed by cooling to 4 degrees C, and addition of antibody against plasma membrane DPP IV. During rewarming, the radioactivity in the complex remained constant. In a similar experiment with [3H]L-fucose, the radioactivity in the immune complex declined rapidly, indicating a defucosylation of the plasma membrane glycoprotein. Using the same experimental design with [3H]D-mannose, the radioactivity in the immune complex remained constant, showing that the core-sugar D-mannose is not cleaved from the membrane glycoprotein. Terminal reglycosylation (refucosylation and resialylation) was demonstrated as follows. Hepatocytes were maintained at 37 degrees C in a medium supplemented with tunicamycin in order to block the de novo synthesis of N-glycosidically bound carbohydrate chains. At 4 degrees C the antibody against DPP IV bound only to cell surface glycoprotein. During the rewarming period at 37 degrees C, radioactivity from [3H]L-fucose and [14C]N-acetyl-D-mannosamine became incorporated into the immune complex. This indicates a fucosylation and sialylation of the glycoprotein originally present at the cell surface. The mechanisms whereby terminal de- and reglycosylation of plasma membrane glycoproteins may occur during membrane recycling are discussed.

Animals↗

PubMed1988

High-performance concanavalin A affinity chromatography of liver and hepatoma membrane proteins.

Although the separation of water-soluble glycoproteins by high-performance (HP) concanavalin A (ConA) affinity chromatography (AC) is feasible, irregularities may be encountered with hydrophobic glycoproteins. The separation of plasma membrane glycoproteins from liver and Morris hepatoma 7777, used as a model, showed that not only the interaction between the lectin and the oligosaccharide portion of the glycoproteins plays a role in the chromatographic process, but also the hydrophobic interactions between sample and lectin and between sample and support. In this, the characteristics of the support, such as surface hydrophobicity and pore size, play an important part. It was found that a portion of the ConA is not covalently bound to the column, especially when elution is carried out with buffers containing detergents. Moreover, some extremely hydrophobic proteins could only be eluted from the column when high concentrations of detergents [1% (w/v) or higher] were applied. Despite these difficulties, four membrane glycoproteins from the liver with apparent molecular weights of 60, 80, 100 and 110-120 kilodaltons could be highly enriched by ConA HPAC. These proteins were further fractionated according to their strength of binding to the ConA and their different hydrophobic characteristics, using various detergents as eluents.

Animals↗

PubMed1988

Characterization of different forms of dipeptidyl peptidase IV from rat liver and hepatoma by monoclonal antibodies.

Nine monoclonal antibodies directed against DPP IV from rat liver plasma membranes were obtained. They recognized four different epitopes (A, B, C and D) of the enzyme. The epitopes A, B and C were located on the outside of the hepatocyte plasma membrane and were shared by DPP IV from hepatoma plasma membrane and the soluble form. Epitope D appeared to be partly inserted in the membrane and was found exclusively in the liver. Epitopes A, B and C and DPP IV revealed by histochemical means showed similar distribution patterns on frozen sections of various rat tissues, while epitope D did not show such a correlation. DPP IV is inserted in liver plasma membrane by two different mechanisms, one being phospholipase C-sensitive, while in hepatoma the enzyme is anchored in this membrane by a phospholipase C-resistant mechanism only.

Animals↗

PubMed1988

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.

Animals↗

PubMed1988

Direct evidence for the binding of rat liver DPP IV to collagen in vitro.

Previous studies have shown that the tripeptide Gly-Pro-Ala, a substrate for dipeptidyl peptidase IV (DPP IV, EC 3.3.14.5), interferes with initial spreading of hepatocytes on a matrix consisting of fibronectin and denatured collagen. In the present investigation we report that the tripeptide as well as the anti-DPP IV antibody inhibits the initial spreading of hepatocytes also on native collagen. This effect appears to be due to the interaction of DPP IV from hepatocyte plasma membrane with native collagen. It is shown in vitro by immunohistochemistry, catalytic histochemistry, and by affinity chromatography of solubilized plasma membrane on collagen-Sepharose that DPP IV has a binding affinity to collagen. This binding does not affect the activity of DPP IV.

Animals↗