Membrane-associated sialidase of rat liver and its decrease in hepatomas

Diagnosis value of membrane glycolipids biochemistry index in intracranial and gastrointestinal tumors

The diagnostic value of membrane glycolipid biochemistry index, the lipid-bound sialic acid (LSA) and total sialic acid (TSA) in cerebrospinal fluid (CSF) was evaluated in 30 intracranial and 65 gastrointestinal tumors. The plasma LSA, TSA and red cell membrane sialic acid (R-SA) in were determined according to the method of Sevenmerhulm. Our results showed that the levels of LSA and TSA in CSF of intracranial tumor patients was higher than that of normal group(p<0.01). The concentration of TSA and LSA in patients with malignant glioma was higher than that of benign meningioma patients(P<0.01). No significance was found between intracranial halmatoma patients and normal control group for levels of membrane glycolipids (p>0.05). Results also found that the plasma LSA, TSA and R-SA of gastric carcinoma were significantly higher than those of control group (p<0.05); while no significant difference was found in the plasma LSA, TSA and R-SA levels between chronic gastritis, gastrohelcoma and normal control group (p>0.05). Plasma LSA, TSA and R-SA levels of gastric carcinoma patient were significantly higher than those of chronic gastritis patients and gastrohelcoma patients(p<0.05). It was also found that plasma LSA, TSA and R-SA contents were significantly higher in large intestine carcinoma patients than in benign in stestine tumor patients (p<0.05) while no significant difference was found between intestine benign tumor and normal control group (p>0.05). The levels of LSA, TSA and R-SA were obviously higher in the patients with metastasis than in the ones without (p<0.05.) The membrane glycolipid biochemistry index LSA and TSA in CSF are sensive markers for diagnosing intracranial tumors. For gastrointestinal malignant tumors the plasma LSA TSA and red blood cell membrane SA may be considered as auxiliary indicators for diagnosis. They can be used for distinguishing benign from malignant tumors.

Serum carbohydrate-deficient transferrin: mechanism of increase after chronic alcohol intake

Carbohydrate-deficient transferrin (CDT) is now considered to be the most sensitive and specific biological marker of alcohol abuse. However, the mechanism by which chronic alcohol consumption causes an elevation of CDT levels in serum is still not understood. Therefore, we fed eight pairs of male rats a nutritionally adequate liquid diet containing either alcohol (36% of energy) or isocaloric dextrose (control) for 4 weeks, after which blood and liver samples were obtained. Serum CDT content in alcohol-treated rats increased by 45% (P < .05) in ethanol-fed animals compared with their corresponding controls. In contrast, in rats fed ethanol, the activities of sialyltransferase (ST), galactosyltransferase (GT), and N-acetylglucosamine transferase (N-AGT), which are glycosyltransferases involved in transferrin carbohydrate side chain synthesis, were diminished by 24% and 40% (P < .05), 23% and 51% (P < .05, .001), and 20% and 26% (P < .05) in total liver homogenates and Golgi fraction (GF) 1, respectively, when expressed as units/100 g body weight. These enzymes were also significantly less active in hepatic GFs 2 and 3. The depression of the transferase activities in ethanol-fed rats appeared to be due, at least in part, to enzyme inactivation by acetaldehyde, whereas ethanol itself was without effect. Similar results were obtained in humans: five alcohol abusers were found to exhibit a 23% decrease in hepatic sialyltransferase and a 41% increase in sialidase activities, respectively, when compared with three nondrinking subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Elimination of non-reactive and weakly reactive human alpha 1-acid glycoprotein after induction of the acute phase response in rats

The disposition of concanavalin A (Con A)-non-reactive and Con A-reactive human alpha 1-acid glycoprotein (AAG) was studied in normal male rats and in acute phase response-activated male rats. Activation of the acute phase response was made using a subcutaneous administration of ethynyloestradiol in sesame oil. This technique increased the endogenous AAG concentration 7-fold. In control rats the two forms of human AAG showed identical kinetics with an average clearance of 5.4 mL h-1 kg-1, terminal half-life of 13.5 h and a volume of distribution (steady state) of 91 mL kg-1. In the acute phase response-activated animals, both the clearance and volume of distribution were larger: the average clearance of the Con A-non-reactive AAG was 10.2 mL h-1 kg-1, the volume of distribution (steady state) 152 mL kg-1 and the terminal half-life 11.7 h. The Con A-reactive AAG had a clearance of 14.7 mL h-1 kg-1, a volume of distribution (steady state) of 262 mL kg-1 and a half-life of 15.8 h. The results indicate that not only does activation of the acute phase response alter the kinetics of AAG but that the change is different for the different types of AAG.

Tumor-promoting phorbol ester induces alterations of sialidase and sialyltransferase activities of JB6 cells

Sialidase and sialyltransferase activities were studied in JB6 mouse epidermal cells before and after exposure to phorbol ester, 12-O-tetradecanoyl phorbol-13-acetate (TPA), which irreversibly induces anchorage-independent growth and tumorigenicity. JB6 cells exhibited sialidase activities toward 4-methylumbelliferyl-alpha-D-N-acetylneuraminic acid (4MU-NeuAc) and gangliosides at pH 4.5 in the particulate fraction but apparently not in the cytosol at pH 4.5 or 6.0. In JB6 cells exposed to TPA and in the anchorage-independent transformants, the sialidase activity toward 4MU-NeuAc was decreased and the activity toward gangliosides was increased compared with those in untreated JB6 cells. Immunological analysis with antisera against membrane-associated sialidases I and II revealed that plasma membrane-associated sialidase I was increased and lysosomal membrane-associated sialidase II was decreased under these conditions. TPA treatment also affected the sialyltransferase activities of JB6 cells: and elevation of the transfer activities toward asialo-orosomucoid and asialo-porcine submaxillary mucin but a reduction of GM3 and GD3 synthase activities were observed on exposure to TPA and in cells transformed by TPA to retain anchorage-independency. These results suggest that an increase in sialic acid bound to glycoproteins and a decrease in that bound to glycolipids may occur in JB6 cells exposed to TPA and in the anchorage-independent transformants.

Neoplastic alteration of a membrane-associated sialidase of rat liver

Rat liver particulate fraction contains two types of membrane-associated and gangliosides-hydrolyzing sialidase, which have been shown to be identical to two membrane-associated sialidases of rat brain (I and II) chromatographically, immunologically and in substrate specificity. Chromatography on AH-Sepharose 4B of the membrane sialidases of rat primary hepatoma induced by 3'-methyl-4-dimethylaminoazobenzene (MeDAB) further revealed that hepatocarcinogenesis induces a marked decrease in sialidase II but no decrease in sialidase I. Using antisera against sialidases I and II of rat brain, immunoprecipitation studies of the solubilized particulate fractions of rat liver and MeDAB-hepatoma gave results similar to those obtained chromatographically. Using the same immunological technique, sialidase II but not sialidase I was found to be decreased in AH109 A hepatoma and in regenerating and fetal liver.

Tumor uptake study of 18F-labeled N-acetylneuraminic acids

In order to develop positron-emitting tracers for imaging metabolic functions of tumors with positron emission tomography, tumor uptake of N-acetyl-3-[18F]fluoroneuraminic acid and N-acetyl-2-deoxy-2,3-di-[18F]fluoroneuraminic acid was investigated in mice or rats. The two tracers showed similar tissue distribution patterns. After i.v. injection of each tracer into mice with an FM3A tumor, the radioactivity was very rapidly cleared from normal and tumor tissues. Only tumor-to-brain and tumor-to-muscle uptake ratios were greater than 1.0 for 2 h. In 7 types of tumor models, no selective tumor uptake of tracers was observed 30 min after injection. The metabolic alteration rate of N-acetyl-3-[18F]fluoroneuraminic acid in FM3A, liver and kidney was very slow. Neither tracer may be suitable for tumor imaging in vivo.