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7202. Glucose administration downregulates lipoprotein lipase activity in vivo: a study using repeated intravenous fat tolerance test
- Creator:
- Eliška Jindřichová, Simona Kratochvílová, and Jan Kovář
- Format:
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- Type:
- article, články, model:article, and TEXT
- Subject:
- Biochemie. Molekulární biologie. Biofyzika, experimentální medicína, lipoproteiny, glukóza, inzulin, triacylglyceroly, experimental medicine, lipoproteins, glucose, insulin, triacylglycerols, intravenous fat tolerance test, 2, and 577
- Language:
- English
- Description:
- Lipoprotein lipase (LPL) is a key factor determining the clearance of triglycerides from the circulation. The enzyme activity is tissue-specifically regulated by insulin, but it is not clear yet how insulin regulates the total LPL activity in the circulation. To answer such question, we measured LPL activity using the intravenous fat tolerance test (IVFTT) that was carried out 1 h before as well as 2 h and 4 h after oral administration of glucose (75 g) in eleven healthy male volunteers. In control experiments, no glucose was given to the subjects. Glucose administration resulted in an expected increase in plasma glucose and insulin and in a suppression of non-esterified fatty acid concentration. The LPL activity assessed in IVFTT as a k2 rate constant did not change in control experiments and decreased to 78 % and 73 % of baseline values 2 h and 4 h after glucose administration, respectively (p=0.01). Similarly, LPL activity measured in the plasma after intravenous injection of heparin at the end of the experiments was 16 % lower (p<0.05) after glucose administration. In conclusion, LPL activity is already downregulated in vivo 2 h after glucose administration. The results of our study indicate that repeated IVFTT is a promising approach for studying acute changes in LPL activity., E. Jindřichová, S. Kratochvílová, J. Kovář., and Obsahuje bibliografii a bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7203. Glucose as a lipolytic agent: studies on isolated rat adipocytes
- Creator:
- Szkudelski, T. and Szkudelska, K.
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- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, glukóza, glucose, adipocytes, 14, and 612
- Language:
- English
- Description:
- In order to elucidate the direct effect of glucose on lipolysis in isolated rat adipocytes, cells were incubated in a buffer with different concentrations of this sugar: 2, 8 or 16 mmol/l. The increase in glucose concentration from 2 mmol/l to 8 or 16 mmol/l enhanced basal lipolysis by 30% and 47 %, respectively. Epinephrine-induced lipolysis (1 m mol/l) was also increased by 31 % and 32 %, when glucose concentration was increased from 2 mmol/l to 8 or 16 mmol/l, respectively. The rise in lipolysis caused by glucose was restricted by H-89 (an inhibitor of protein kinase A, 30 µmol/l), but insulin (1 nmol/l) had no inhibitory action. The augmentation of lipolysis by glucose did not require its metabolism (as demonstrated using 2-deoxyglucose) and was due to the action of this sugar on the final steps of the lipolytic cascade, particularly on protein kinase A. However, short-term exposure of adipocytes to higher glucose concentrations did not restrict the inhibitory action of insulin on lipolysis induced by epinephrine., T. Szkudelski, K. Szkudelska., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7204. Glucose release as a response to glucagon in rat hepatocyte culture: involvement of NO signaling
- Creator:
- Hassan Farghali, Hodis, J., Nikolína Kutinová-Canová, Petr Potměšil, Eva Kmoníčková, and Zdeněk Zídek
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- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, farmakologie, oxid dusnatý, glukagon, jaterní buňky, pharmacology, nitric oxide, glucagon, liver cells, glycogenolysis, 14, and 612
- Language:
- English
- Description:
- Glucagon and α-adrenergic-induced glycog enolysis is realized via the agonist/adenylyl cyclase/cAMP/protein kinase signaling pathway or via the activation of phosphorylase kinase by the mobilized calcium that supports the inhibition of glycogen synthase, respectively. The role of nitric oxide (NO) in this process has not been extensively studied. The present work was directed to the question whether NO is produced during glucagon-induced glycogenolysis in rat hepatocyte in a similar way like α-adrenoceptor stimulation. Glycogen-rich hepatocyte cultures were used. NO production (NO2-) was assessed under the influence of glucagon, dibutyryl cyclic AMP (db-cAMP), forskolin, the nitric oxide synthase (NOS) inhibitors Nω-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine, and the NO donor S-nitroso-N-acetyl penicillamine (SNAP). Inducible NOS (iNOS) mRNA was examined by reverse transcription-polymerase chain reaction. Glycogenolysis was followed up by estimation of medium glucose levels. The amount of glucose and NO2- released by glycogen-rich hepatocytes was increased as a result of glucagon, db-cAMP, forskolin and SNAP treatments. iNOS gene expression was upregulated by glucagon. Glycogenolysis that occurs through glucagon receptor stimulation involves NO production downstream of transduction pathways through an isoform of NO synthase. The present and previous studies document possible involvement of NO signaling in glycogenolytic response to glucagon and adrenergic agonists in hepatocytes., H. Farghali, J. Hodis, N. Kutinová-Canová, P. Potměšil, E. Kmoníčková, Z. Zídek., and Obsahuje bibliografii a bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7205. Glutamate Induces Different Neuronal Conditioned Responses than ACPD When Used As a Locally Ionophoresed Unconditioned Stimulus in the Cat Motor Cortex
- Creator:
- Woody, Ch. D.
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- Type:
- article, studie, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, fyziologie člověka, human physiology, Conditioning, Learning, Pavlov, Metabotropic receptors, Excitatory amino acids, 14, and 612
- Language:
- English
- Description:
- Single unit recordings were made from the motor cortex of conscious cats with glass micropipettes that allowed ionophoretic application of 0.5 M glutamate in 2 M NaCl or 0.5 M ACPD (1S,3R-1-amino-cyclopentane-1,3-dicarboxylic acid, a mGluR agonist) in 2 M NaCl. Activity in response to a 70 dB click (1 ms rectangular pulse to loudspeaker) was studied before, during, and immediately after applying each agent locally as a paired US (90 nA current 570 ms after click for 300 ms in combination with glabella tap). A 70 dB hiss sound was presented 4.4 sec after the click as a discriminative stimulus (DS). CS and DS were presented 10 times initially (adaptation); then CS, US plus tap, and DS (approximately 10 times as conditioning); and then CS and DS (2-10 times to test post-conditioning). Glutamate potentiated the mean, early, 8-16 ms response to the click after conditioning (t=18.2, p<0.0001), but not the baseline activity which decreased from a mean of 17 spk/sec to 7 spk/sec (t=3.71, p<0.001). Baseline activity increased to 31 spk/sec when glutamate was applied during conditioning (t=3.30, p<0.005). ACPD reduced the intermediate, 64-72 ms response to the click after conditioning (t=8.18, p<0.0001), and potentiated the late 104-112 ms response (t=15.4, p<0.0001). Baseline activity was slightly increased after conditioning with ACPD. Saline did not potentiate the response to click. The results indicate that glutamate agonists that differ in their receptor affinities can induce different CRs when used as locally applied USs to condition neuronal responses to a click CS in the motor cortex of cats., Ch. D. Woody., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7206. Glutathione reductase is inhibited by acetaminophen-glutathione conjugate in vitro
- Creator:
- Tomáš Roušar, Patrik Pařík, Otto Kučera, Bartoš, M., and Zuzana Červinková
- Format:
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, fyziologie, physiology, acetaminophen toxicity, glutathione reductase, glutathione, hepatotoxicity, 14, and 612
- Language:
- English
- Description:
- The aim of the present work was to investigate a new mechanism likely contributing to the toxic action of acetaminophen, especially to explore the possible inhibition of glutathione reductase through an acetaminophen-glutathione conjugate (APAP-SG). APAP-SG conjugate was synthesized by organic synthesis and purified by column chromatography. The inhibitory effect of the conjugate on two types of glutathione reductase (from yeasts and rat hepatocytes) was tested spectrophotometrically. We found that the enzyme activity was reduced similarly after the treatment with 2.96 mM acetaminophenglutathione conjugate in both yeast and hepatocyte glutathione reductases (GR); the enzyme activity was inhibited to 52.7±1.5 % (2.4±0.3 mU/ml) in yeast GR (control activity was 5.6±0.3 mU/ml) and to 48.1±8.8 % (2.2±0.2 mU/ml) in rat hepatocytes lysate GR (control activity was 5.2±0.2 mU/ml). In addition, the enzyme activity (from hepatocytes lysate) was decreased to 79±7 %, 67±2 % and 39±7 %, in 0.37, 1.48 and 3.7 mM concentration of the conjugate, respectively. We found that glutathione reductase, the essential enzyme of the antioxidant system, was dose-dependently inhibited by the product of acetaminophen metabolism - the conjugate of acetaminophen and glutathione., T. Roušar ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7207. Glutathione S-transferase does not play a role in multidrug resistance of L1210/VCR cell line
- Creator:
- Viera Boháčová, Kvačkajová, J., Miroslav Barančík, Drobná, Z., and Albert Breier
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- Type:
- article, články, journal articles, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, fyziologie, physiology, P-glycoprotein, multidrug resistance, L1210 leukemic cell lines, cytostatic drugs, 14, and 612
- Language:
- English
- Description:
- Multidrug resistance of cancer cells is often accompanied by the (over)expression of integral plasma membrane P-glycoprotein, an ATP-dependent transport pump for diverse unrelated compounds. The glutathione detoxification system represents another mechanism that may be involved in multidrug resistance. In the multidrug-resistant L1210/VCR cell line obtained by long-term adaptation of parental L1210 cells to vincristine, an increased expression of P-glycoprotein has previously been established. In this paper, we investigated if the glutathione detoxification system is also involved in the multidrug resistance of these cells. L1210/VCR cells with resistance induced by adaptation to vincristine were also found to be cross-resistant to vinblastine, actinomycin D, mitomycin C, doxorubicin and cyclophosphamide. The resistance of the above cells to vincristine and doxorubicin was accompanied by a depression of drug accumulation (which has not yet been established for other drug). L1210/VCR cells are able to survive better than sensitive cells under conditions when glutathione was depleted by L-buthionine sulfoximine. Nevertheless, L-buthionine sulfoximine did not influence the resistance of L1210/VCR cells to vincristine. Moreover, the presence of sublethal concentrations of cytostatics neither changed the IC50 value of resistant cells to L-buthionine sulfoximine nor the cytoplasmic activity of glutathione S-transferase, the crucial enzyme of glutathione detoxification system. All the above findings indicate that the glutathione detoxification system is not involved in the mechanisms that ensure the multidrug resistance phenotype of L1210/VCR cells., V. Boháčová, J. Kvačkajová, M. Barančík, Z. Drobná, A. Breier., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7208. Glycine oxidase and serine dehydratase in green leaves of wheat and maize and their possible role in photosynthetic metabolism
- Creator:
- Igamberdiev, A.U. and Bykova, N.V.
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Description:
- The actívities of glycine oxidase (GO) and serine dehydratase (SD) were revealed in green leaves of wheat and maize. The enzymes were extracted by ammonium sulfáte fractionation. GO localized in chloroplast and cytosolic fraction was most active at pH 8.0. Its activity was 1.5-2.0 times higher in wheat than in maize and it declined with leaf aging. The enzyme converts glycine into glycollate and ammonium ion being flavine dependent and generating H2O2. We propose that it is an L-amino-acid oxidase (EC 1.4.3.2) with a higher specificity to glycine. The activity of SD (EC 4.2.1.13) localized in chloroplasts was maximum at pH 7.0-7.2, it was also higher in wheat than in maize. Pyruvate was determined as a product of enzymatic conversion of L-serine. SD and GO actívities were not revealed in etíolated leaves.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7209. Glycolytic enzymes in polyamine-treated bovine retina
- Creator:
- Venza, I., Valenti, A., Ruggeri, P., Denaro, L., and Teti, D.
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- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, polyaminy, sítnice, polyamines, retina, LDH isoenzymes, MDH isoenzymes, 14, and 612
- Language:
- English
- Description:
- The retina is characterized by glycolysis under aerobic conditions, mediated by lactate dehydrogenase isoenzyme-5 (LDH-5) as well as by the soluble isoenzyme of malate dehydrogenase. Bovine retina LDH and MDH isoenzymes and their activities were studied after polyamine treatment. Our results showed that LDH-5 isoenzyme presented the highest activity in untreated as well as in putrescine-treated retina. Decreased activity was present when the retina was treated with spermidine or spermine. It was demonstrated that retinic LDH-5 had a high affinity for lactate which enabled the isoenzyme to be more effective than the other LDH isoenzymes in the conversion of NADH to NAD. Therefore, the putrescine enhancing LDH-5 activity appeared to be capable of stimulating NAD-mediated rhodopsin regeneration. Putrescine induced a marked increase of both MDH isoenzymes - soluble (s-MDH) and mitochondrial (m-MDH), while spermine and spermidine mostly affected the soluble form of the enzyme. Putrescine induced a three-fold increase in s-MDH and m-MDH activities, while spermine and spermidine induced a four to five-fold increase in s-MDH. These results document the differential effects of polyamine treatment on LDH and MDH isoenzyme activities., I. Venza, A. Valenti, P. Ruggeri, L. Denaro, D. Teti., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
7210. Glycotoxines, carbonyl stress and relevance to diabetes and its complications
- Creator:
- Turk, Z.
- Format:
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, diabetes mellitus, glyoxal, carbonyl stress, methylglyoxal, 3-deoxyglucosone, advanced glycation end-product, 14, and 612
- Language:
- English
- Description:
- A large body of evidence has implicated reactive carbonyl compounds as glycotoxic mediators of carbonyl stress. This review is focused on the pathophysiological effects of α-oxoaldehydes in diabetes and related complications, summarizing the state-of-the-art on the endogenously produced carbonyls methylglyoxal, glyoxal and 3-deoxyglucosone, formed as glycolytic intermediates during metabolic conversion of glucose, via Maillard reaction by degradation of glycated proteins, and during lipid peroxidation process. Their role in the advanced glycation process and detrimental effects on vascular tissue are discussed., Z. Turk., and Obsahuje bibliografii a bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public