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1,526 records · Page 85Linked to original sources
PubMed1996

[Possibilities and limitations of drugs to protect the liver].

In this paper preventive liver protective agents for the prophylaxis of hepatopathies due to functional stress, and curative protective agents for therapy of existing liver damage are distinguished. Preventive liver protective agents are key substances in the metabolism of proteins, carbohydrates, lipids, and sulfur. For curative liver protective agents, inhibitors of RNA and protein synthesis, calcium antagonists and inhibitors of sulfhydryl (-SH) containing enzymes are proposed and substantiated.

Amino Acids↗
PubMedDate not supplied

[Functional characteristics of fructose-2,6-bisphosphate system in the liver during experimental streptozotocin diabetes].

The activity of phosphofructokinase-2, fructose, 1,6-bisphosphatase, glucokinase, and also the level of fructose 2,6-bisphosphate and glycogen were examined in the liver of normal, and streptozotocin-diabetic rats. It was shown that the activity of phosphofructokinase-2 was decreased in the liver of diabetic rats. Besides that the activity determined at pH 6.6 (the "active" or unphosphorylated enzyme form) was 3-fold reduced whereas the "total" enzyme activity as measured at pH 8.5 was lowered 1,7-fold. The phosphofructokinase-2 activity assay at two pH values allows to estimate a degree of phosphorylation of bifunctional enzyme which is markedly enhanced in diabetes. The fall of the bifunctional enzyme k in case activity is accompanied by the lowered fructose 2.6-bisphosphate level, increased fructose 1,6-bisphosphatase activity that in turn favours the liver tissue glycolysis inhibition and gluconeogenesis enhanced in diabetes.

Animals↗
PubMedDate not supplied

[The effect of fructose-1,6-diphosphate, cytochrome c and their combination on the size of the necrotic area in transient myocardial ischemia].

The effect of fructose-1, 6-diphosphate (200 mg/kg), cytochrome C (20 mg/kg) and their combinations on the size of the zone of necrosis 4 and 72 h after 15-min transitory myocardial ischemia was studied. Combination of the compounds under study inhibited considerably the development of post-occlusion and reperfusion arrhythmias and reduced the size of necrosis 4 h after their administration as prophylactic and arresting measures (to 23.8 +/- 2.9 and 29.3 +/- 3.6% of the ischemic zone, respectively, in 42.8 +/- 3.8% in the control). A combined course of cytochrome C and fructose diphosphate also limited the size of the necrotic zone 72 h after transitory ischemia. Separate single administration of fructose diphosphate and cytochrome C caused no essential changes in the size of myocardial necrosis recorded 72 h after transitory myocardial ischemia.

Animals↗
PubMed1996

Aggregation of banana pyrophosphate fructose 6-phosphate 1-phosphotransferase by glycerol.

Addition of glycerol during purification of banana (Musaceae, Musa cavendishii) pyrophosphate fructose 6-phosphate 1-phosphotransferase [(PFP), EC 2.7.1.90] initiated molecular aggregation of the enzyme. The aggregation process was dependent on the glycerol concentration. The native enzyme (66 kDa molecular mass) showed enhanced activity at 3% (V/V) or less of glycerol concentration. Glycerol concentration between 4 and 5% (V/V) affected a gradual and sequential aggregation of native form of the enzyme. These aggregated forms had molecular masses of 135, 200 and 270 kDa. The 135 and 200 kDa forms were stable for about 72 hrs and prolonged storage over 2 weeks resulted in the formation of the 270 kDa form. Concentration over 5% could reduce the time required for aggregation. Fru2.6 bis P activated the enzyme over ten fold, but did not help in the aggregation process. Studies on the role of glycerol on PFP specific activity suggested a difference in the activation process compared to that by Fru2.6bis P. Replacement of Hepes buffer by Tris increased the Fru2.6 bis P requirement for maximum activation by around 10 fold. Removal of glycerol from the buffer media resulted in almost complete inactivation of the enzyme.

Cellulose↗
PubMed1977

Characterization of pyruvate kinase from the liver of a patient with aberrant erythrocyte pyruvate kinase, PK Nagasaki.

The characterization of the L-type PK were made of PK extracted from the liver of a patient with congenital hemolytic anemia associated with an erythrocyte PK variant, PK Nagasaki. The L-type PK of PK Nagasaki showed the following parameters: slow migration on electrophoresis, high Km for PEP without F-1,6-P2, less activation by F-1,6-P2, normal Km for ADP, high utilization of UDP, acidic pH optimum, and instability to urea and heat. These tests served to differentiate this L-type PK variant from the other variants previously reported. At the same time, both the Km for PEP with F-1,6-P2 saturation and the electrophoretic mobility of L-type PK were found to be different from those of the erythrocyte PK and PK Nagasaki. Though the liver cell, with regard to L-type PK, has only the less functional and less stable mutant L-type PK there is no evidence of liver dysfunction or damage, although there is chronic hemolytic anemia.

Adolescent↗
PubMedDate not supplied

[Effect of oral inulin administration on the fructose 2,6-biphosphate level in the liver tissue of rats with streptozocin diabetes].

The influence of oral inulin administration on glucose and fructose content in blood, glucose and ketone bodies in urine, and fructose-2,6-diphosphate content in liver was investigated in rats with streptozotocin diabetes. Short-term administration (during 5-6 days) of 0.5% inulin solution caused three-fold increase of blood fructose compared with control, normalisation of blood glucose and disappearance of glucose- and ketoneuria. The level of fructose-2,6-di-phosphate in liver increased to the control level. Inulin administration during 12 days caused five-fold increase of blood fructose compares with control, glucose level increased up to the level of uncurred diabetes (22 mmol/1), glucose- and ketoneuria appeared. The content of fructose-2,6-diphosphate in the liver decreased to diabetic level.

Administration, Oral↗
PubMed1997

Dexfenfluramine modulates hepatic glycogen metabolism by a calcium-dependent pathway.

In this study, the mechanism of action of dexfenfluramine (DEXF) at the hepatic level was investigated. The drug is shown to bind to the alpha 1-adrenergic receptor and to increase intracellular calcium in isolated rat hepatocytes, thereby activating phosphorylase via a calcium-dependent mechanism. Moreover, phosphorylase activation by DEXF was inhibited by different agents that interfere with the alpha 1-adrenergic signalling system: prazosin, phorbol 12 alpha-myristate 13 beta-acetate (PMA), and DEXF itself. We also show that phosphorylase activation induced by catecholamines and analogues (epinephrine, phenylephrine), whose actions are mediated by a calcium-dependent mechanism, was counteracted by the drug in the submillimolar range (0.1-1 mM). The activation of glycogenolysis by the drug is accompanied by a stimulation of the glycolytic flux (54% increase in lactate plus pyruvate accumulation), consistent with an increase in fructose-2,6-bisphosphate (F-2,6-BP) levels (36%). These results indicate that the interaction of DEXF with the alpha 1-adrenergic receptor channels glucose 6-phosphate derived from glycogen away from glucose production into the glycolytic pathway.

Adrenergic Agonists↗
PubMedDate not supplied

Separation of phosphorylated sugars using capillary electrophoresis with indirect photometric detection.

Adenosine monophosphate (AMP) and naphthalene disulfonate (NDS) have been characterized as electrolytes for the indirect photometric detection of phosphorylated sugars and other organophosphorus compounds of biochemical interest. This work has resulted in the CE separation on an uncoated capillary using 5 mM AMP and 100 mM boric acid at pH 7.2 of six metabolites (glucose-6-phosphate [G6P], fructose-6-phosphate [F6P]), fructose-1,6-bisphosphate [F-1,6-P], dihydroxyacetone phosphate [DHAP], glyceraldehyde-3-phosphate [G3P], and 2-phosphoglycerate [2-PG] or 3-phosphoglycerate [3-PG]) found in the glycolytic pathway. The detection limits using a 5-sec injection time were between 0.5 and 1 mg/L for these compounds, with the exception of G3P. Resolution between 3-PG and 2-PG is possible by the addition of magnesium ion, although the separation time is longer. A successful separation of five monophosphorylated sugars (G6P, F6P, ribose-5-phosphate [R5P], sucrose-6-phosphate [S6P], and 2-PG) has been performed using the same conditions as for the glycolytic pathway separation. A separation of bisphosphorylated sugars (glucose-1,6-bisphosphate [G-1,6-P],F-1,6-P, ribulose-1,5-bisphosphate [Ru-1, 5P], and sedoheptulose-1,7-bisphosphate [S-1, 7P]) could not be performed with AMP unless magnesium chloride was added. With NDS, a separation of these bisphosphorylated sugars can be obtained without the addition of magnesium chloride.

Dihydroxyacetone Phosphate↗
PubMedDate not supplied

Analysis of glycolysis metabolites by capillary zone electrophoresis with indirect UV detection.

The glycolysis metabolites glucose 6-phosphate (G6-P), fructose 6-phosphate (F6-P), fructose 1,6-bisphosphate (F1,6-BP), fructose 2,6-bisphosphate (F2,6-BP), glyceraldehyde phosphate (GAP), dihydroxyacetone phosphate (DHAP), phosphoenolpyruvate (PEP), pyruvate, and lactate were analyzed by capillary zone electrophoresis (CZE) with indirect UV detection. The chromophores phthalic acid, sorbic acid, and 4-hydroxybenzoic acid were studied as background electrolytes. Both detection sensitivity and resolution were found to depend on the pH and the concentration of the carrier electrolyte. Optimum separation and detection of the phosphate compounds were accomplished upon reversal of electroendosmotic flow (EOF) with OFM Anion-BT (Waters Corp., Milford, MA) at a concentration of 4-6 mM 4-hydroxybenzoic acid, pH 11.6-12.0, with the detection wave-length set at 280 nm. The highly alkaline pH allowed the successful separation of the isomers F6-P and G6-P, as well as F1,6-BP and F2,6-BP, respectively. The effect of sample ionic strength on the detection limits of G6-P, F6-P, F1,6-BP, and F2,6-BP was also investigated: These limits ranged from 1 to 3 microM in both low- and high-ionic-strength samples. However, high Mg2+ concentrations in the sample led to a progressive loss of resolution between F1,6-BP and F2,6-BP, unless the inlet reservoir was replenished with fresh electrolyte after every injection. Linearity of detection was observed over one to two orders of magnitude.

Dihydroxyacetone Phosphate↗
PubMed1999

Fructose-1,6-diphosphate in the treatment of oleander toxicity in dogs.

Oleander, a flowering plant that grows in the Mediterranean and southern US, contains the cardiac glycosides oleandrin, digitoxigenin and nerium, which inhibit Na(+)-K+ ATPase. Clinical manifestations of oleander toxicity include gastrointestinal irritation, marked hyperkalemia, A-V block, ventricular dysrhythmia, and not uncommonly death. Because fructose-1,6-diphosphate (FDP) has been shown to attenuate digoxin toxicity, we determined whether this agent would be effective in the treatment of the toxicity of these similarly-structured cardiac glycosides. Anesthetized dogs (n = 12) were infused i.v. for 5 min with 40 mg oleander extract/kg and then 6 dogs randomly selected from that group received a 50 mg/kg bolus of 10% FDP followed by a constant infusion. The other control animals received the same dosage of 10% dextrose. Within 5 min after oleander administration, all dogs developed dysrhythmias. The FDP-treated animals reverted to sinus rhythm within 1.58 +/- 0.15 h; none in the control group returned to sinus rhythm. One control dog died at 3 h from ventricular fibrillation. Marked hyperkalemia was observed in the control group; plasma K+ remained unchanged in the FDP group. Throughout the 4 h experimental period the FDP group maintained normal arterial pressures; in the control dextrose group, pressures were profoundly depressed. Cardiac output declined in both groups but remained higher in the FDP group. To determine the mechanism whereby FDP attenuates oleander toxicity, we studied the in vitro effect of FDP on oleander poisoned myocardial sarcolemmal membranes. At concentrations of 1 and 2 mg oleander inhibited Na(+)-K+ ATPase activity and addition of 500 microM FDP restored myocardial sarcolemmal Na(+)-K+ ATPase function. FDP effectively prevented hyperkalemia, reversed dysrhythmias and improved hemodynamics in vivo in this canine model of oleander toxicity and also restored sarcolemmal Na(+)-K+ ATPase activity in vitro.

Animals↗