Carbohydrate Metabolism In Rat Liver Research Articles

The hepatoprotective properties of an extract from the brown alga Saccharina japonica

This study examines the influence of an extract from the brown alga Saccharina japonica on the antiradical activity and biochemical indices of lipid and carbohydrate metabolism in rat liver during carbon tetrachloride (CTC) poisoning. The Saccharina extract contributed to a reduction of the level of free-radical processes, effective relief of tissue hypoxia, and the restoration of the neutral lipid fractions pattern. The therapeutic effectiveness of the algal preparation appeared to be greater than that of the widely adopted reference hepatoprotector Legalon.

Effect of orally administered secondary autoxidation products of linoleic acid on carbohydrate metabolism in rat liver

The effects of orally administered secondary autoxidation products of linoleic acid in rat liver were investigated. Their administration led to two toxic effects on hepatic carbohydrate metabolism, as compared to the administration of saline or linoleic acid used as controls. One effect was depletion of glucose 6-phosphate and fructose 6-phosphate caused by the reduction of glycolysis and glycogenolysis, accompanied by decreases in glycogen synthesis and pentose phosphate cyclic activity. The reduction in these metabolic systems seems unlikely to occur because phosphofructokinase was regulated by ATP or citrate enzymatically, because their accumulation in the liver was not detected in the secondary products. Another toxic effect was the depletion of oxaloacetate and isocitrate caused by the reduction in enzyme activity of the mitochondrial citrate cycle. On the basis of these results, the hepatotoxic effects of secondary products are discussed as follows: the incorporated secondary products impaired the activities of hexokinase and phosphoglucomutase in the liver. The reduction in these enzyme activities resulted in the depletion of glucose 6-phosphate and fructose 6-phosphate, which led ultimately to decreases in the activities of phosphofructokinase, the pentose phosphate cycle, and glycogen synthesis. Moreover, the secondary products disturbed the mitochondrial membrane, resulting in a decrease in the activity of the citrate cycle, which was accompanied by depletion of its metabolites.

Biochemical correlation of glycogen content and activity of some enzymes of carbohydrate metabolism in rat liver during early stages of carcinogenesis.

The livers of rats treated for 12 weeks with N-nitrosomorpholine (80 mg/1 drinking water) were investigated on the day of carcinogen withdrawal (12 + 0 weeks) and 8 weeks after cessation of treatment (12 + 8 weeks). The glycogen content in relation to the DNA and protein content of the liver and the activities of glycogen synthetase, glycogen phosphorylase, glucose-6-phosphatase, and glucose-6-phosphate dehydrogenase were determined in the liver homogenates. The glycogen content of the livers was slightly elevated at both times investigated. Phosphorylase and synthetase activities showed no clear alterations in livers of treated animals as compared with controls. Glucose-6-phosphatase activity was significantly reduced at 12 + 0 weeks and returned to normal values at 12 + 8 weeks. The activity of glucose-6-phosphate dehydrogenase was unchanged at 12 + 0 weeks, but exhibited a significant increase at 12 + 8 weeks. Polyacrylamide gel electrophoresis with staining of the gels by an assay specific for the glucose-6-phosphate-dehydrogenase-catalysed reaction revealed the same pattern of active bands in treated and untreated animals but with higher activities in two bands originating from extracts of nitrosomorpholine-treated livers.

Histochemical studies on carbohydrate metabolism in rat liver after galactosamine administration.

The development of hepatitis, induced in 48 rats by the administration of galactosamine (GalN) in varying doses, was studied with the use of substrate and enzyme histochemical techniques. The so-called atypical glycogen, which is at first highly resistant to diastase, was shown to be digestible after deamination. The increasing accumulation of atypical glycogen during the course of GalN-hepatitis conceals the loss of normal glycogen when the PAS-reaction is used. Nevertheless glycogenolysis could also be demonstrated by the increasing activity of phosphorylase. The acid phosphatase activity was progressively diminished, which was interpreted as signifying early lysosomal damage. G6Pase activity remained nearly constant but SDH showed a decrease in activity after 12 h. These histochemical results are considered to provide deeper insight into the pathological mechanism of GalN-hepatitis.

Effects of progesterone on some enzymes of fat and carbohydrate metabolism in rat liver

The known effect of progesterone on carbohydrate metabolism prompted a study of some of the hepatic “lipogenic” and “gluconeogenic” enzymes in rats treated with progesterone. Several enzymes providing lipid precursors (phosphofructokinase, malic enzyme, glucose-6-phosphate dehydrogenase, and citrate cleavage enzyme) showed increased specific activity. These changes may represent insulin effects. Specific activity of phosphoenolpyruvate carboxykinase, usually associated with control of gluconeogenesis, was also increased. The latter is compatible with increased capability for glycogenesis, which is recognized as a progesterone effect.

The influence of phenobarbital on carbohydrate metabolism in developing rat liver

The influences of phenobarbital (PB) on enzymes of the carbohydrate metabolism in rat liver are examined during pre- and postnatal development. The following results are obtained: (1) PB generally increases G-6-Pase before and after birth. (2) Both the active and the inactive forms of phosphorylase are increased significantly during the prenatal periods. During the postnatal periods, mainly the active form of phosphorylase is influenced by PB. (3) Total glycogen synthetase is increased by PB during prenatal development but decreased during postnatal development. (4) The activity of alpha-glucosidase is increased during the prenatal period. (5) The activity of F-6-PK and 6-PGDH are decreased during the prenatal periods and G-6-PDH activity is decreased during both pre- and postnatal periods.

Effect of ochratoxin A on carbohydrate metabolism in rat liver

The effect of ochratoxin A on the carbohydrate metabolism of liver has been investigated in rats. A marked depletion of glycogen in liver and an increase of serum glucose in ochratoxin A-treated rats were noted. Glycogen synthetase (I and total) activities were reduced. In contrast, phosphorylase a activity was increased in the liver of ochratoxin A-treated rats. Decrease in incorporation of [ 14C]-glucose into hepatic glycogen confirmed the findings using unlabeled glucose. These results implied that depletion of hepatic glycogen in ochratoxin A-treated rats was attributed to the inhibition of the active transport of glucose into liver tissue, suppression of glycogenesis, and acceleration of glycogenolysis.

The modifying effect of manganese on the enzymic profiles and pathways of carbohydrate metabolism in rat liver and adipose tissue during development

The effect of Mn 2+ on the pattern of emergence of enzymes in rat liver and adipose tissue was studied in weaned rats given a milk diet (high fat) or sucrose-casein diet (high carbohydrate) for three weeks. Addition of Mn 2+ to the high fat diet was associated with induction of key glycolytic, lipogenic and pentose pathway enzymes in both liver and adipose tissue; parallel increases were found in the incorporation of [1- 14C] glucose into lipid and CO 2. Mn 2+ induced a change in the profile of enzyme activity similar in pattern to that found in rats given a high sucrose diet or that produced by insulin treatment. Mn 2+ appears partially to overcome the regulatory feed-back mechanisms of the high fat diet and to provide a signal for the coordinated increase of glucose catabolic and lipogenic processes.

The Effect of Lipid Peroxide on the Lipid and Carbohydrate Metabolism in Rat Liver

Feeding tests were carried out on rats to clarify the mechanisms of fatty liver formation induced by autoxidized methyl linoleate. Lipid peroxides prepared by autoxidation of highly purified methyl linoleate were given orally to rats. Triglyceride and glycogen contents in liver were determined and enzyme activities including triglyceride synthetase and α-glycerophosphate dehydrogenase were also examined. The following results were obtained. 1. Triglyceride accumulation in rat liver fed autoxidized methyl linoleate was observed. 2. Increase in triglyceride content in rat liver was soon followed by the decrease of hepatic glycogen. 3. When rats were starved prior to introduction of autoxidized methyl linoleate, hepatic triglyceride accumulation did not occur. 4. The activities of α-glycerophosphate dehydrogenase and triglyceride synthetase in liver, and those of glutamic oxalacetic transaminase and leucine aminopeptidase in plasma were practically similar among the rats of test groups fed fresh or autoxidiz...

Effect of nicotamide on the regulation of carbohydrate metabolism in rat liver.

Male Sprague-Dawley rats received an intraperitoneal injection of 500 mg nicotinamide/kg body weight. One, two, five and eight hours later, the livers were frozen rapidly in liquid N2. The following metabolites were analyzed: lactate, pyruvate, glycerol-I-phosphate, dihydroxyacetone-phosphate, malate, oxaloacetate, adenine nucleotides, glucose, glucose-6-phosphate, fructose-1,6-diphosphate, phospho-enolpyruvate, acetyl-Coenzyme A, nicotinamide-adenine dinucleotide, nicotinamide-adenine dinucleotide phosphate. In addition, the levels of glycogen and triglycerides were determined.

Effects of xylitol on carbohydrate metabolism in rat liver treated with carbon tetrachloride or alloxan.

Effects of xylitol on carbohydrate metabolism in rat liver treated with carbon tetrachloride or alloxan.

Glucose oxidation by liver slices from the domestic fowl. Activity of the phosphogluconate-oxidative pathway.

The value of the quotient, 14CO2 liberated from glucose-1-14C over 14CO2 liberated from glucose-6-14C, for chicken liver slices has been determined. It did not deviate appreciably from unity for slices from (a) immature and sexually mature females, (b) a group of females at intervals during their transition from sexual immaturity to sexual maturity, (c) immature males, and (d) immature females treated by injection with estradiol monobenzoate. Incubation of the liver slices under anaerobic conditions reduced CO2 liberation to very low values and approximately doubled the quotient. Incubation in the presence of arsenite reduced oxidation but increased the quotient about fourfold. Incubation under anaerobic and aerobic conditions, with addition of pyruvate, increased the quotient value.It is concluded that the phosphogluconate-oxidative pathway, if active at all in chicken liver, plays a subordinate role in carbohydrate metabolism in this tissue compared with its role in carbohydrate metabolism in rat liver.