scholarly journals Lipogenesis in rat and guinea-pig isolated epididymal fat-cells

1974 ◽  
Vol 140 (2) ◽  
pp. 211-224 ◽  
Author(s):  
E. David Saggerson
Keyword(s):  
Fatty Acids ◽  
Guinea Pig ◽  
Malate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Aspartate Aminotransferase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Fat Cells ◽  
Hexose Monophosphate ◽  
Hexose Monophosphate Pathway ◽  
Rat Fat Cells

Fat-cells were prepared from rat and guinea-pig epididymal adipose tissue and compared on the basis of the intracellular distributions and activities of enzymes and with respect to their utilization of various U-14C-labelled substrates for lipogenesis. 1. Compared with the rat, guinea-pig extramitochondrial enzyme activities differed in that aconitate hydratase, alanine aminotransferase, ATP–citrate lyase, lactate dehydrogenase, NAD–malate dehydrogenase, NADP–malate dehydrogenase and phosphoenolpyruvate carboxykinase activities were appreciably lower, whereas aspartate aminotransferase, glucose 6-phosphate dehydrogenase, NADP–isocitrate dehydrogenase and 6-phosphogluconate dehydrogenase activities were appreciably higher. Mitochondrial activities of citrate synthase, NADP–isocitrate dehydrogenase and pyruvate carboxylase were appreciably lower, whereas mitochondrial activities of aspartate aminotransferase, glutamate dehydrogenase, NAD–malate dehydrogenase and phosphoenolpyruvate carboxykinase were higher in the guinea pig compared with the rat. 2. In general guinea-pig fat-cells incorporated acetate and lactate into fatty acids more readily than rat fat-cells, whereas rat fat-cells incorporated glucose and pyruvate more readily than guinea-pig fat-cells. 3. Acetate stimulated the incorporation of glucose into fatty acids in rat fat-cells, but had no appreciable effect upon this process in guinea-pig fat-cells. Acetate greatly decreased the incorporation of lactate into fatty acids in cells from both species. 4. Lactate/pyruvate ratios produced by incubation of guinea-pig cells with glucose+insulin were very low compared with those found with rat cells under the same conditions. 5. With glucose (+insulin) or with glucose+acetate (+insulin) as substrates guinea-pig cells produced enough NADPH by the hexose monophosphate pathway to satisfy the NADPH requirements of lipogenesis. In rat fat-cells under the same conditions, hexose monophosphate-pathway NADPH provision was not sufficient to meet the requirements of lipogenesis. 6. These results are discussed, particularly in relationship to the disposition of cytosolic reducing equivalents in the cells.

scholarly journals Distribution of activities of aspartate aminotransferase isoenzymes and malate dehydrogenase in guinea pig retinal layers.

1987 ◽  
Vol 35 (6) ◽  
pp. 669-674 ◽  
Author(s):  
C D Ross ◽  
D A Godfrey
Keyword(s):  
Guinea Pig ◽  
Malate Dehydrogenase ◽  
Aspartate Aminotransferase ◽  
Energy Production ◽  
Outer Nuclear Layer ◽  
Plexiform Layer ◽  
Inner Plexiform Layer ◽  
Retinal Layers ◽  
Metabolic Reactions ◽  
The Difference

Distributions of activity of the cytosolic (cAAT) and mitochondrial (mAAT) isoenzymes of aspartate aminotransferase and of malate dehydrogenase (MDH) were determined in guinea pig retinal layers. The distribution of total AAT activity (tAAT = cAAT + mAAT) and of mAAT activity correlated well (r = 0.88-0.91) with the distribution of MDH activity. mAAT activity was highest in the inner segments of the photoreceptors; there was a greater than twelve-fold difference between activity in that layer and in the inner retinal layers. cAAT activity was also highest in the inner segments, but the difference between the activity in the inner segments and the other layers was not nearly as great as with mAAT. cAAT activity was also relatively high in the outer nuclear layer, outer plexiform layer, and part of the inner plexiform layer. The high activity of cAAT, mAAT, and MDH in the inner segments indicates that all of these enzymes are involved in metabolic reactions related to energy production and/or to photoreceptive processes in the outer segments and, therefore, that the enzymes are probably involved in energy-related metabolism at synapses. However, other functions, including those related to neurotransmission, are not excluded.

Depressed lipogenesis induced by cold stress

1960 ◽  
Vol 199 (3) ◽  
pp. 449-452 ◽  
Author(s):  
E. J. Masoro
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Cold Stress ◽  
Carbohydrate Metabolism ◽  
Liver Cells ◽  
Hexose Monophosphate ◽  
Hexose Monophosphate Pathway ◽  
Liver Homogenates ◽  
Fasted Rats ◽  
Low Rate

Liver homogenates were prepared from control, cold-fed and cold-fasted rats. Homogenates from control and cold-fed rats synthesized fatty acids to about the same extent. However, homogenates from cold-fasted rats converted far less acetate-1-C14 to fatty acids than homogenates from control and cold-fed rats. Previous studies showed that lipogenesis is depressed in liver slices from both cold-fed and cold-fasted rats. Probably the fact that lipogenesis is inhibited in the intact liver cells of cold-fed rats is not the result of reduced levels of fatty acid-synthesizing enzymes but is the result of an unfavorable cofactor environment; the evidence indicates that a low rate of TPNH generation via the hexose monophosphate pathway of carbohydrate metabolism causes the reduction in lipogenic activity. The failure in lipogenesis in the liver cells of the cold-fasted rat appears to result from quite a different cause than that of the cold-fed rat. The most likely reason for the low rate of lipogenesis in the liver of cold-fasted rats appears to be the loss of the fatty acid-synthesizing enzymes; however, the possibility that this lipogenic defect is related to the lack of a cofactor—as yet undiscovered— cannot be discounted.

NADPH AND NADH OXIDATION BY GUINEA PIG POLYMORPHONUCLEAR LEUCOCYTES

1963 ◽  
Vol 41 (2) ◽  
pp. 427-434 ◽  
Author(s):  
G. Y. N. Iyer ◽  
J. H. Quastel
Keyword(s):  
Hydrogen Peroxide ◽  
Guinea Pig ◽  
Nadph Oxidase ◽  
Oxidase Activity ◽  
Enzyme System ◽  
Polymorphonuclear Leucocytes ◽  
Hexose Monophosphate ◽  
Manganese Ions ◽  
Hexose Monophosphate Pathway ◽  
Stimulation Of

A homogenate of guinea pig polymorphonuclear leucocytes contains an enzyme system capable of oxidizing, in presence of oxygen, NADPH and NADH with the formation of hydrogen peroxide. The enzyme is much more active towards NADPH than to NADH. The presence of manganese ions strongly enhances the oxidase activity. It is suggested that the release of the NADPH oxidase in the leucocytes, during phagocytosis, accounts for the stimulation of the hexose monophosphate pathway that occurs in phagocytosis.

scholarly journals The effect of starvation and starvation followed by feeding on enzyme activity and the metabolism of [U−14C]glucose in liver from growing chicks

1968 ◽  
Vol 108 (4) ◽  
pp. 667-673 ◽  
Author(s):  
Alan G. Goodridge
Keyword(s):  
Fatty Acids ◽  
Enzyme Activity ◽  
Fatty Acid ◽  
Isocitrate Dehydrogenase ◽  
Malic Enzyme ◽  
Acid Synthesis ◽  
Minor Role ◽  
Hexose Monophosphate ◽  
Hexose Monophosphate Shunt ◽  
Cleavage Enzyme

1. The conversion of [U−14C]glucose into carbon dioxide, cholesterol and fatty acids in liver slices and the activities of ‘malic’ enzyme, citrate-cleavage enzyme, NADP-linked isocitrate dehydrogenase and hexose monophosphate-shunt dehydrogenases in the soluble fraction of homogenates of liver were measured in chicks that were starved or starved then fed. 2. In newly hatched chicks the incorporation of [U−14C]glucose and the activity of ‘malic’ enzyme did not increase unless the birds were fed. The response to feeding of [U−14C]glucose incorporation into fatty acids increased as the starved chicks grew older. 3. Citrate-cleavage enzyme activity increased slowly even when the newly hatched chicks were unfed. On feeding, citrate-cleavage enzyme activity increased at a much faster rate. 4. In normally fed 20-day-old chicks starvation decreased the incorporation of [U−14C]glucose into all three end products and depressed the activities of ‘malic’ enzyme and citrate-cleavage enzyme. Re-feeding increased all of these processes to normal or higher-than-normal levels. 5. In both newly hatched and 20-day-old chicks starvation increased the activity of isocitrate dehydrogenase and feeding or re-feeding decreased it. 6. Very little change in hexose monophosphate-shunt dehydrogenase activity was observed during the dietary manipulations. 7. The results indicate that increased substrate delivery to the liver is the principal stimulus to the increased rate of glucose metabolism observed in newly hatched chicks. The results also suggest that changes in the activities of ‘malic’ enzyme and citrate-cleavage enzyme are secondary to an increased flow of metabolites through the glucose-to-fatty acid pathway and that the dehydrogenases of the hexose monophosphate shunt play a minor role in NADPH production for fatty acid synthesis.

scholarly journals The activities and intracellular distribution of nicotinamide-adenine dinucleotide phosphate-malate dehydrogenase, phosphoenolpyruvate carboxykinase and pyruvate carboxylase in rat, guinea-pig and rabbit tissues

1975 ◽  
Vol 146 (2) ◽  
pp. 329-332 ◽  
Author(s):  
D E Saggerson ◽  
C J Evans
Keyword(s):  
Adipose Tissue ◽  
Guinea Pig ◽  
Malate Dehydrogenase ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Intracellular Distribution ◽  
Kidney Cortex ◽  
Carboxylase Activity ◽  
Liver And Kidney

1. Measurements are presented of the activity and intracellular distribution of phosphoenolypruvate carboxykinase, pyruvate carboxylase and NADP-malate dehydrogenase in rat, guinea-pig and rabbit liver and kidney cortex, together with previously obtained measurements of these enzymes in adipose tissue. 2. In all three tissues pyruvate carboxylase activity was greatest in the rat and lowest in the rabbit. 3. Guinea pig and rabbit were very similar to each other with respect to the extramitochondrial-mitochondrial distribution of phosphoenolpyruvate carboxykinase in all three tissues. 4. NADP-malate dehydrogenase was present in all three tissues in the rat, present in kidney cortex and adipose tissue in the guinea pig and absent from all tissues examines in the rabbit.

scholarly journals Acinar zonation of cytosolic but not organelle-bound activities of phosphoenolpyruvate carboxykinase and aspartate aminotransferase in guinea-pig liver

1990 ◽  
Vol 271 (2) ◽  
pp. 387-391 ◽  
Author(s):  
L Agius ◽  
D Tosh
Keyword(s):  
Enzyme Activity ◽  
Guinea Pig ◽  
Aspartate Aminotransferase ◽  
Human Liver ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Cell Populations ◽  
Similar Distribution ◽  
Subcellular Compartment ◽  
Whole Cells ◽  
Intracellular Compartmentation

In human liver, unlike in rat liver, there is no apparent acinar heterogeneity of total cellular activity of phosphoenolpyruvate carboxykinase [Wimmer, Luttringer & Columbi (1990) Histochemistry 93, 409-415]. Since the intracellular compartmentation of phosphoenolpyruvate carbonxykinase differs in rat and human liver, we examined the acinar heterogeneity of cytosolic and organelle-bound activities of this enzyme in the guinea pig, which shows a more similar intracellular compartmentation of enzyme activity to human liver than does the rat. Cytosolic phosphoenolpyruvate carboxykinase activity was higher in periportal than in perivenous hepatocytes, whereas the organelle-bound activity was similar in the two cell populations. Aspartate aminotransferase and alanine aminotransferase activities showed a similar distribution to phosphoenolpyruvate carboxykinase, with a higher cytosolic activity in periportal than in perivenous hepatocytes but a similar organelle-bound activity in the two cell populations. Data on the acinar zonation of enzymes determined in whole cells or tissue should be interpreted cautiously if the enzyme activity is present in more than one subcellular compartment.

NADPH AND NADH OXIDATION BY GUINEA PIG POLYMORPHONUCLEAR LEUCOCYTES

1963 ◽  
Vol 41 (1) ◽  
pp. 427-434 ◽  
Author(s):  
G. Y. N. Iyer ◽  
J. H. Quastel
Keyword(s):  
Hydrogen Peroxide ◽  
Guinea Pig ◽  
Nadph Oxidase ◽  
Oxidase Activity ◽  
Enzyme System ◽  
Polymorphonuclear Leucocytes ◽  
Hexose Monophosphate ◽  
Manganese Ions ◽  
Hexose Monophosphate Pathway ◽  
Stimulation Of

A homogenate of guinea pig polymorphonuclear leucocytes contains an enzyme system capable of oxidizing, in presence of oxygen, NADPH and NADH with the formation of hydrogen peroxide. The enzyme is much more active towards NADPH than to NADH. The presence of manganese ions strongly enhances the oxidase activity. It is suggested that the release of the NADPH oxidase in the leucocytes, during phagocytosis, accounts for the stimulation of the hexose monophosphate pathway that occurs in phagocytosis.

scholarly journals Lipogenesis in rabbit isolated fat-cells

1974 ◽  
Vol 142 (3) ◽  
pp. 477-482 ◽  
Author(s):  
E. David Saggerson
Keyword(s):  
Fatty Acids ◽  
Guinea Pig ◽  
Metabolic Pathways ◽  
Pyruvate Carboxylase ◽  
Acid Synthesis ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Fat Cell ◽  
Carboxylase Activity ◽  
Low Activity

1. Fat-cells isolated from rabbit perirenal adipose tissue were incubated with the following U-14C-labelled substrates: 5mm-glucose (+insulin), 5mm-pyruvate, 5mm-lactate, 5mm-glucose+5mm-acetate (+insulin), and the relative rates of incorporation of these substrates into glyceride fatty acids determined. In general total rates of fatty acid synthesis were similar whatever substrate was supplied to the cells. 2. Rabbit fat-cells incorporated [U-14C]acetate into fatty acids and CO2 as well in the absence of glucose as in the presence of this substrate. 3. The disposition of the utilization of glucose-derived carbon through various metabolic pathways was determined. 4. Extramitochondrial and mitochondrial activities were determined for 11 enzymes. The cells contained a very low activity of pyruvate carboxylase, undetectable NADP–malate dehydrogenase activity and a high mitochondrial phosphoenolpyruvate carboxylase activity. 5. Various rabbit fat-cell metabolic parameters based on the measurement of14C incorporation and enzyme activity were compared with the same parameters previously measured in rat and guinea-pig fat-cells. In general guinea pig occupied a position between rat and rabbit with respect to these parameters. 6. The profiles of substrate incorporation into fatty acids and of relative enzyme activities in rabbit fat-cells indicated that the operation of a ‘citrate-cleavage’ pathway may not be obligatory for the supply of lipogenic acetyl units.

scholarly journals Effect of insulin, catecholamines and calcium ions on phospholipid metabolism in isolated white fat-cells

1980 ◽  
Vol 186 (3) ◽  
pp. 781-789 ◽  
Author(s):  
J. Adolfo García-Sáinz ◽  
John N. Fain
Keyword(s):  
Fatty Acids ◽  
Phosphatidic Acid ◽  
Inhibitory Effect ◽  
Phospholipid Metabolism ◽  
Ionophore A23187 ◽  
Fat Cells ◽  
Adrenergic Stimulation ◽  
White Fat ◽  
Adrenergic Activation ◽  
Rat Fat Cells

The incorporation of [32P]Pi into phosphatidylinositol by rat fat-cells was markedly increased in the presence of adrenaline. Phosphatidic acid labelling was also increased, but to a lesser extent. These effects are due to α1-adrenergic stimulation since they were unaffected by propranolol, blocked by α-blockers in the potency order prazosin«phentolamine<yohimbine and mimicked by methoxamine. The α-adrenergic stimulation of phosphatidylinositol labelling did not require extracellular Ca2+, which supports the hypothesis that an increased turnover of phosphatidylinositol is involved in α-adrenergic activation of Ca2+ entry. Insulin and the ionophore A23187 gave a small increase in 32P labelling of phosphatidylinositol in Ca2+-free medium containing 1mm-EGTA. The increases due to insulin or ionophore A23187 were abolished if 2.5mm-Ca2+ was added to medium containing EGTA. However, the increases in labelling of phosphatidylinositol due to α-adrenergic amines were still evident in medium containing EGTA and Ca2+. Lipolytic agents such as corticotropin, dibutyryl cyclic AMP, adrenaline in the presence of phentolamine and isoproterenol decreased [32P]Pi incorporation into phosphatidylinositol, phosphatidylethanolamine and phosphatidic acid. This inhibitory effect may be secondary to accumulation of intracellular unesterified fatty acids, since it was decreased by incubating fewer cells in medium with 6 rather than 3% albumin and was restored by the addition of oleate to the medium. The incorporation of [32P]Pi into phosphatidylcholine was unaffected by lipolytic agents. The data suggest that there is an inhibition of the synthesis of certain phospholipids in the presence of lipolytic agents, which may be secondary to intracellular accumulation of unesterified fatty acids.

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