scholarly journals Factors affecting the permeability of isolated fat-cells from the rat to [42K]potassium and [36Cl]chloride ions

1970 ◽  
Vol 117 (3) ◽  
pp. 615-621 ◽  
Author(s):  
M. C. Perry ◽  
C. N. Hales
Keyword(s):  
Initial Phase ◽  
Chloride Ions ◽  
Fat Cells ◽  
Adrenocorticotrophic Hormone ◽  
Isolated Fat Cells ◽  
Free Medium ◽  
Fat Cell ◽  
Factors Affecting ◽  
Exchange Diffusion ◽  
High K

1. The effluxes of 42K+ and 36Cl− from isolated fat-cells from the rat were studied under a variety of conditions known to affect the metabolism of the cells. 2. 42K+ efflux from isolated fat cells was increased in a Na+-free–high-K+ medium and decreased in a K+-free medium. The existence of K+ exchange diffusion across the fat-cell membrane is suggested. 3. 36Cl− efflux from isolated fat-cells was decreased when the Cl− component of the wash medium was replaced by acetate. The basal 36Cl− efflux is suggested to be partly by Cl− exchange diffusion and partly in company with a univalent cation. 4. A variety of lipolytic stimuli, adrenaline, adrenocorticotrophic hormone, N-6,O-2′-dibutyryladenosine cyclic 3′:5′-monophosphate and theophylline, increased 42K+ efflux from isolated fat-cells. The adrenaline stimulation was biphasic; an initial, rapid and transient increase in 42K+ loss from the fat-cells was followed by a slower, more prolonged, increase in 42K+ efflux. The initial phase was inhibited by phentolamine but not by propranolol. 5. Insulin increased 42K+ efflux only after preincubation with the cells.

scholarly journals The properties and extracellular location of 5′-nucleotidase of the rat fat-cell plasma membrane

1975 ◽  
Vol 146 (3) ◽  
pp. 625-633 ◽  
Author(s):  
A C Newby ◽  
J P Luzio ◽  
C N Hales
Keyword(s):  
Plasma Membrane ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Fat Cell ◽  
Cell Plasma Membrane ◽  
Intact Cells ◽  
Low Concentrations ◽  
Cell Plasma ◽  
Atp Analogues ◽  
Extracellular Location

1. A phosphohydrolase specific for 5′-nucleotides was characterized by using a particulate fraction from isolated fat-cells. 2. The activity of intact cells towards 5′-AMP was studied. 3. The activity in either situation had the same KM for AMP (45 muM) and was inhibited by low concentrations of ATP (less than 50 muM), but less potently by the ATP analogues AMP-P(CH2)P(adenylyl (β γ-methylene)diphosphonate) and AMP-P)NH)P (adenylylimidodiphosphate). 4. Homogenization of intact fat-cells caused no increase in activity and at least 85% of the activity was recovered in the particulate preparation. 5. The preparation of fat-cells used in this work was not freely permeable to AMP. 6. The ability of intact fat-cells to hydrolyse AMP implies that 5′-nucleotidase is an ectoenzyme in fat-cells. 7. Concentrations of ATP 100 times lower than intracellular concentrations inhibit the enzyme when added extracellularly to intact fat-cells, implying that this effect is also medicated at the extracellular face of the membrane. 8. Antibodies raised to whole liver cells and whole fat-cells inhibit 5′-nucleotidase in intact cells. 9. Incubation of intact fat-cells with adrenaline (1 mug/ml) or insulin (50 mui.u./ml) failed to alter the KM or Vmax. of the enzyme.

scholarly journals Effect of nutrition on subcellular localization of rat fat-cell lipoprotein lipase

1978 ◽  
Vol 172 (2) ◽  
pp. 239-245 ◽  
Author(s):  
A Vanhove ◽  
C Wolf ◽  
M Breton ◽  
M C Glangeaud
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Plasma Membranes ◽  
Total Activity ◽  
Normal Diet ◽  
Epididymal Adipose Tissue ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Fat Cell ◽  
Intact Tissue

This study supports the possibility for multiple subcellular forms of lipoprotein lipase. 1. The total activity of lipoprotein lipase per g of intact epididymal adipose tissue from fed rats is much higher than that from starved rats. 2. The isolated fat-cells of fed and of starved rats have lipoprotein lipase of almost the same activity per g of fat-pads. The isolated fat-cells of starved rats have a much higher proportion of total activity per g of the intact tissue than do those of fed rats. 3. Under the conditions of homogenization used, only a small proportion of the total activity per g of intact tissue from fed rats was associated with the fat layer which floated to the top of the homogenate during low-speed centrifugation. The different proportions of the specific enzyme activity found in each subcellular fraction are described. 4. Lipoprotein lipase from plasma membranes and microsomal fractions from starved and fed rats was purified by affinity chromatography. 5. The total activity of microsomal lipoprotein lipase per g of intact adipose tissue is enhanced by a normal diet. 6. In intact epididymal adipose tissue from fed rats, the activity per g of tissue of lipoprotein lipase of plasma membranes is much higher than that in the same fraction from starved rats. By contrast, the activities per g of tissue in plasma membranes obtained from starved or from fed rats by collagenase treatment were similar.

scholarly journals Rates of efflux and intracellular concentrations of potassium, sodium and chloride ions in isolated fat-cells from the rat

1969 ◽  
Vol 115 (5) ◽  
pp. 865-871 ◽  
Author(s):  
M. C. Perry ◽  
C. N. Hales
Keyword(s):  
Atomic Absorption Spectrophotometry ◽  
Chloride Ions ◽  
Intracellular Water ◽  
Epididymal Adipose Tissue ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
First Order ◽  
Inulin Space ◽  
Intracellular Concentrations ◽  
Water Space

1. The metabolism of K+, Na+ and Cl− has been investigated in isolated fat-cells prepared from the epididymal adipose tissue of rats. 2. Methods are described for measuring the intracellular water space, the rates of loss of intracellular 42K+, 22Na+ and 36Cl− and the intracellular concentrations of K+, Na+ and Cl− in isolated fat-cells. 3. The intracellular water space, measured as the [3H]water space minus the [carboxylic acid−14C]inulin space, was 3·93±0·38μl./100mg. cell dry wt. 4. The first-order rate constants for radioisotope effluxes from isolated fat-cells were 0·029min.−1 for 42K+, 0·245min.−1 for 22Na+ and 0·158min.−1 for 36Cl−. 5. The intracellular concentrations of K+, Na+ and Cl− were 146m-equiv./l., 18·6±2·9m-equiv./l. and 43±2·4m-equiv./l. respectively. 6. The total intracellular K+ content of isolated fat-cells was determined by atomic-absorption spectrophotometry to confirm the value obtained from the radioisotope-efflux data. 7. The ion effluxes from isolated fat-cells were: K+, 1·5pmoles/cm.2/sec., Na+, 1·6pmoles/cm.2/sec., and Cl−, 2·4pmoles/cm.2/sec. 8. The membrane potential of isolated fat-cells calculated from the Cl− distribution ratio was −28·7mv.

scholarly journals Colchicine inhibition of the heparin-stimulated release of clearing-factor lipase from isolated fat-cells

1975 ◽  
Vol 152 (3) ◽  
pp. 717-720 ◽  
Author(s):  
A Cryer ◽  
A McDonald ◽  
E R Williams ◽  
D S Robinson
Keyword(s):  
Lipase Activity ◽  
Incubation Medium ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Fat Cell

When isolated fat-cells are incubated at 25 degrees C in serum-based media containing glucose, insulin and heparin, the rise that occurs in the clearing-factor lipase activity of the incubation medium is inhibited by colchicine. The rise in the fat-cell clearing-factor lipase activity that occurs during similar incubations in the absence of heparin is not affected by colchicine.

Level of physical fitness and adipocyte lipolysis in humans

1984 ◽  
Vol 56 (5) ◽  
pp. 1157-1161 ◽  
Author(s):  
J. P. Despres ◽  
C. Bouchard ◽  
R. Savard ◽  
A. Tremblay ◽  
M. Marcotte ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Exercise Training ◽  
Lipolytic Activity ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Fat Cell ◽  
Marathon Runners ◽  
Trained Subjects ◽  
Male Subjects ◽  
Sedentary Subjects

The present experiment was conducted to study the influence of exercise training on adipose tissue lipolytic activity and to identify the amount of training required to induce maximal adaptation in humans. Fifty-one male subjects were divided into three groups according to their training regimen: 1) sedentary subjects (SS) (n = 21); 2) trained subjects (TS) (n = 15) who had exercised during a period of 20 wk, 5 days/wk, 45 min/session; and 3) experienced marathon runners (MR) (n = 15) who ran an average of 120 km/wk for many years. Biopsies of fat were performed in the suprailiac region after an overnight fast. Adipocyte diameter (AD) and epinephrine-stimulated lipolysis ( ESL ) were assessed on collagenase-isolated fat cells. A lower AD was noted in the MR group compared with the two other groups. Basal lipolysis (BL) and ESL were significantly higher in TS and MR than in controls. Moreover, BL values were comparable in the two trained groups, whereas ESL in the TS group was higher than in the MR group. These results indicate that training increases suprailiac fat cell lipolysis, which seems to adapt maximally within about 4 mo.

Altered expression of C/EBP family members results in decreased adipogenesis with aging

2001 ◽  
Vol 280 (6) ◽  
pp. R1772-R1780 ◽  
Author(s):  
Iordanes Karagiannides ◽  
Tamara Tchkonia ◽  
Deborah E. Dobson ◽  
Claire M. Steppan ◽  
Patrice Cummins ◽  
...  
Keyword(s):  
Cell Function ◽  
Family Members ◽  
Dominant Negative ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Fat Tissue ◽  
Fat Cell ◽  
Inhibitory Protein ◽  
Altered Expression ◽  
Enhancer Binding Protein

Fat mass, adipocyte size and metabolic responsiveness, and preadipocyte differentiation decrease between middle and old age. We show that expression of CCAAT/enhancer binding protein (C/EBP)-α, a key regulator of adipogenesis and fat cell function, declined substantially with aging in differentiating preadipocytes cultured under identical conditions from rats of various ages. Overexpression of C/EBPα in preadipocytes cultured from old rats restored capacity to differentiate into fat cells, indicating that downstream differentiation-dependent genes maintain responsiveness to regulators of adipogenesis. C/EBPα-expression also decreased with age in fat tissue from three different depots and in isolated fat cells. The overall level of C/EBPβ, which modulates C/EBPα-expression, did not change with age, but the truncated, dominant-negative C/EBPβ-liver inhibitory protein (LIP) isoform increased in cultured preadipocytes and isolated fat cells. Overexpression of C/EBPβ-LIP in preadipocytes from young rats impaired adipogenesis. C/EBPδ, which acts with full-length C/EBPβ to enhance adipogenesis, decreased with age. Thus processes intrinsic to adipose cells involving changes in C/EBP family members contribute to impaired adipogenesis and altered fat tissue function with aging. These effects are potentially reversible.

Effect of dihydroergotamine and growth hormone on lipolysis in isolated fat cells of the rat

1970 ◽  
Vol 48 (5) ◽  
pp. 324-326 ◽  
Author(s):  
N. Hotta ◽  
O. V. Sirek ◽  
A. Sirek
Keyword(s):  
Growth Hormone ◽  
Bovine Growth Hormone ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Cell Preparation ◽  
Fat Cell ◽  
Lipolytic Effect ◽  
Mechanism Of Interaction

Dihydroergotamine (DHE) is lipolytic in the isolated fat cell preparation of Rodbell. Bovine growth hormone (GH) alone or in combination with dexamethasone causes lipolysis that is barely measurable. The combination of GH and DHE is equally ineffective. Incubation of fat cells with all three agents produces massive lipolysis that is by far greater than the sum of effects of individual components. The augmented lipolytic effect is suppressible with puromycin. The exact mechanism of interaction between GH, dexamethasone, and DHE has to be elucidated.

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.

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