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At least 19 recordsLinked to original sources
PubMedDate not supplied

[Characteristics of the function of the pentosephosphate pathway in the mucous membrane of the gastrointestinal tract of rats with vitamin PP deficiency and stress-induced ulcer].

Characteristics of the pentosephosphate pathway function were studied in the gastrointestinal mucosa of niacin-deficient rats with stress-induced ulcers. A decreased activity of the pentosephosphate pathway oxidative enzymes was recorded in rats with PP-hypovitaminosis. The levels of oxidated and reduced forms of NADP were lowered while transketolase activity and aldopentose amount rose. Activity of the nonoxidative component of the pentosephosphate pathway increased while that of oxidative reactions decreased in rats with stress-induced ulcers. Stress produced in the presence of niacin-deficiency did not significantly influence the pentosephosphate pathway in the gastroduodenal mucosa.

Animals↗
PubMedDate not supplied

[Effect of aggregation inducers and inhibitors on the pentosephosphate pathway enzymes of glucose conversion in the thrombocytes].

Experiments with rabbit platelets in vitro revealed differences in the effect of the aggregation inducers (ADP and thrombin) and the aggregation inhibitor cyclic AMP on the activity of the enzymes of pentosephosphate pathway of glucose oxidation. ADP and thrombin decrease significantly the activity of glucoso-6-phosphate dehydrogenase (G-6-PDH) and riboso-5-phosphate-metabolizing enzymes (R-5-PME) in platelets during aggregation, whereas cyclic AMP produces no appreciable effect on the G-6-PDH activity, but increases significantly the R-5-PME activity. ADP decreases and cyclic AMP raises substantially the activity of R-5-PME. The differences were also revealed in the effects produced by cyclic AMP and cyclic GMP on the enzymes of pentosephosphate pathway of glucose oxidation. Unlike cyclic AMP, cyclic GMP decreased significantly the activity of G-6-PDH. The activity of R-5-PME and cyclic GMP transketolase was more pronounced than that of cyclic AMP. Like cyclic AMP, cyclic GMP differs from ADP and thrombin in the action produced on the enzymes of pentosephosphate pathway of glucose oxidation.

Adenosine Diphosphate↗
PubMedDate not supplied

[Function of the pentosephosphate pathway in the rat brain during one-time administration of various doses of ethanol].

A rate of alterations in the enzymatic activity of pentosephosphate pathway and content of glucose in rat brain depended on a dose of administered ethanol. The alcohol inhibitory effect on the enzymatic activity was localized mainly in the brain steam. Impairment of the pentosephosphate pathway functions in alcohol intoxication demonstrated the pathway importance in realization of ethanol effects in nervous tissue.

Animals↗
PubMed1979

Pentosephosphate shunt activity of rat pancreatic islets: its dependence on glucose concentration.

Although several attempts have been made to establish a relationship between glucose concentration and pentosephosphate shunt (PPS) activity of pancreatic islets in vitro, no such relationship has been found. Recently it has been shown that exogenous insulin, when added in vitro, inhibited islet PPS activity. Since it was possible that the failure to detect such a relationship was due to insulin released into the incubation medium, we reinvestigated the subject, introducing GPAIS (guinea pig antiinsulin serum) to bind insulin in the medium. When five islets were incubated with 16.7 mM glucose for 90 min, the absolute rate as well as the percentage of islet PPS activity were found to be significantly higher (P less than 0.05) in the presence of GPAIS than in its absence. In the presence of GPAIS, the absolute rate and the percentage of islet PPS activity increased in a dose-related manner (18, 43, and 124 pmol/five islets.90 min and 2.3%, 3.2%, 9.4%, respectively) when the glucose concentration was raised from 5.6 to 11.1 and 16.7 mM. Our data, therefore, indicate that the activity of islet PPS activity in vitro depends on the concentration of glucose, provided that insulin does not accumulate in the incubation medium. This suggests that PPS activity might play a role in glucose-induced insulin secretion. However, whether the PPS contributes to the secretory mechanism by producing a signal for insulin secretion or by forming cofactors required by the secretory mechanism remains to be established.

Animals↗
PubMedDate not supplied

[Effect of insulin of dehydrogenases of pentosephosphate pathway and content of free fatty acids in rat kidney].

After administration of insulin into rats activity of dehydrogenases of pentosephosphate pathway was not altered in cortex and medulla of kidney as distinct from the liver tissue. Concentration of free fatty acids was slightly lower in soluble fraction of kidney cortex than in blood plasma and higher than in preparation from kidney medulla. Alterations in content of free fatty acids were not observed in the preparations of kidney of rats with alloxan diabetes.

Animals↗
PubMedDate not supplied

[Role of the vagus nerves in regulating the activity of the pentosephosphate carbohydrate metabolic pathway in the thymus and mesenteric lymph nodes].

Activity of key enzymes of pentosephosphate pathway glucose-6-phosphate dehydrogenase (G6PD) and transketolase was similar in extracts of thymus and mesenteric lymphatic ganglia. Within four weeks after dissection of vagus nerve at the level of thyroid gland the specific activity of G6PD and the total activity of the enzymes metabolizing ribose-5-phosphate were not altered in the tissue studied. The transketolase activity was inhibited in thymus tissue and lymphoid cells after right-side vagotomy. The pH-dependence of the transketolase reaction was studied in thymus extracts. After vagotomy the enzymatic activity was lower at all the pH values as compared with controls; the enzyme optimum activity was found at pH 7.5-7.8.

Animals↗
PubMedDate not supplied

[Circadian rhythm of the activity of limiting enzymes of the pentosephosphate pathway in rat liver].

Activities of glucose-6-phosphate dehydrogenase and transketolase from rat liver tissue exhibited circadian rhythms with the maximal rate at 22 and 6 o'clock and minimal--at 14 o'clock (per 1 mg of liver protein and per 1 g of the tissue). Decrease in total activity of glucose-6-phosphate dehydrogenase at the day time was due to distinctly lowered activity of the minor isoenzyme components. Differences in activity of the enzymes were more than 100% at the maximal and minimal periods. The data obtained earlier and in the experiment reported herein suggest that alterations in activity of pentosephosphate pathway enzymes, observed in the states of stress reactions, are presumed to be compensated if they are within the limits of extreme circadian variations; activity of the enzymes, exceeding the circadian variation values, indicates decompensation in the state of carbohydrate turnover.

Animals↗
PubMed1984

The role of old age in the effects of glucose on insulin secretion, pentosephosphate shunt activity, pyridine nucleotides and glutathione of rat pancreatic islets.

In pancreatic islets of adult (three month) and old (24 month) rats the effect of glucose on glucose oxidation, pyridine nucleotides, glutathione and insulin secretion was studied. DNA content was similar in both groups of animals; however, islets of old rats exhibited 30% less insulin content. While glucose-induced (16.7 mM) insulin secretion in islets of old rats was approximately 50% less than in islets of adults, no significant difference was observed in the insulin releasing effect of theophylline (1 mM). Although islet production of 14CO2 in the presence of 16.7 mM glucose increased equally in both groups, elevation of glucose failed to increase the percentage of total glucose oxidation via the pentose phosphate shunt in islets of old rats. Elevation of glucose increased the NADPH/NADP and the NADH/NAD ratio in both groups of islets in a similar manner. The effect of glucose on the GSH/GSSG ratio revealed a dose-related increase in the islets of adult rats, whereas islets of old rats did not respond to elevation of glucose. Our data seem to indicate that the lower secretory response of islets of old rats is related to the failure of glucose to increase the GSH/GSSG ratio. In contrast the insulin release induced by theophylline does not appear to depend on islet thiols.

Aging↗
PubMed2003

A flux model of glycolysis and the oxidative pentosephosphate pathway in developing Brassica napus embryos.

Developing oilseeds synthesize large quantities of triacylglycerol from sucrose and hexose. To understand the fluxes involved in this conversion, a quantitative metabolic flux model was developed and tested for the reaction network of glycolysis and the oxidative pentose phosphate pathway (OPPP). Developing Brassica napus embryos were cultured with [U-13C6]glucose, [1-13C]glucose, [6-13C]glucose, [U-13C12]sucrose, and/or [1,2-13C2]glucose and the labeling patterns in amino acids, lipids, sucrose, and starch were measured by gas chromatography/mass spectrometry and NMR. Data were used to verify a reaction network of central carbon metabolism distributed between the cytosol and plastid. Computer simulation of the steady state distribution of isotopomers in intermediates of the glycolysis/OPPP network was used to fit metabolic flux parameters to the experimental data. The observed distribution of label in cytosolic and plastidic metabolites indicated that key intermediates of glycolysis and OPPP have similar labeling in these two compartments, suggesting rapid exchange of metabolites between these compartments compared with net fluxes into end products. Cycling between hexose phosphate and triose phosphate and reversible transketolase velocity were similar to net glycolytic flux, whereas reversible transaldolase velocity was minimal. Flux parameters were overdetermined by analyzing labeling in different metabolites and by using data from different labeling experiments, which increased the reliability of the findings. Net flux of glucose through the OPPP accounts for close to 10% of the total hexose influx into the embryo. Therefore, the reductant produced by the OPPP accounts for at most 44% of the NADPH and 22% of total reductant needed for fatty acid synthesis.

Amino Acids↗
PubMedDate not supplied

[Enzyme activity of citrate, glyoxylate and pentosephosphate cycles during synthesis of citric acids by Candida lipolytica].

The activity of key enzymes of the citrate and glyoxylate cycles was compared in yeast cells during intensive synthesis of citric acids and in its absence in the course of growth of Candida lipolytica on glucose ("glucose" yeast cells) and on hexadecane ("hexadecane" yeast cells). Citrate and isocitrate were found to be formed by the yeast in the tricarboxylic acid cycle. The ability of the yeast for "overproduction" of citrate and isocitrate during its growth on glucose and hexadecane depends on the high activity of the key enzyme of cycle, citrate synthase, as compared with the activity of other enzymes of the tricarboxylic acid cycle. Citrate predominated among excreted acids during growth on glucose in conditions of nitrogen deficiency while isocitrate prevailed during growth on hexadecane. The predominating synthesis of citrate in the first case seems to be related to a lower activity of aconitase in the "glucose" cells as compared with the "hexadecane" cells.

Aconitate Hydratase↗
PubMedDate not supplied

[Effect of antipheins on indices of the activity of the pentosephosphate pathway for carbohydrate transformation].

Experiments set up on rabbits showed that with their intravenous administration in a dose of 10 mg/kg antiphein, aethimizol, allilnorantipheins and propylnorantiphein catalize the activity of the pentosophosphate mode of the carbohydrates transformation. The character of the action and the intensity of the effect depend on the features distinguishing the chemical structure of the substances, of particular importance here being changed conformation of the molecule.

Animals↗