Activation and inhibition of lipolysis in isolated fat cells by various inhibitors of cyclic AMP phosphodiesterase

1972 ◽  
Vol 273 (1-2) ◽  
pp. 62-74 ◽  
Author(s):  
U. Schwabe ◽  
S. Berndt ◽  
R. Ebert
Keyword(s):  
Cyclic Amp ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Cyclic Amp Phosphodiesterase

Distribution of cyclic AMP phosphodiesterase in adipose tissue from trained rats

1986 ◽  
Vol 61 (4) ◽  
pp. 1546-1551 ◽  
Author(s):  
K. A. Kenno ◽  
J. L. Durstine ◽  
R. E. Shepherd
Keyword(s):  
Cyclic Amp ◽  
Specific Activity ◽  
Particulate Fraction ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Sprague Dawley ◽  
Enzyme Form ◽  
Cyclic Amp Phosphodiesterase ◽  
Sprague Dawley Rats ◽  
Michaelis Constants

Fat cells were isolated from sedentary and exercise trained female Sprague-Dawley rats and cyclic AMP phosphodiesterase (cyclic AMP-PDE) activities were determined from crude homogenates of the fat cells in the whole homogenate, P5, P48, and S48 fractions. Exercise training resulted in a significant increase in the mean specific activity of cyclic AMP-PDE (pmol X min-1 X mg-1) from the whole homogenate and S48 fraction at cyclic AMP concentrations of 4, 8, and 16 microM and in the P48 fraction at 8 and 16 microM cyclic AMP. Cyclic AMP-PDE kinetic plots according to Lineweaver-Burk for the calculation of Michaelis constants (Km) and maximum enzyme velocities (Vmax) were nonlinear, indicating both a low and high enzyme form. The Michaelis constants were significantly lower in trained rats than those of its control for the high Km form of cyclic AMP-PDE in the whole and soluble fractions and for the low Km form of the P5 particulate fraction. The Vmax of the high Km form of the P48 particulate fraction from trained animals was also significantly higher than that found in its control. Phosphodiesterase inhibition by methylxanthines in the various fractions was similar in both trained and sedentary animals. These changes in specific activity, Michaelis constants, and Vmax of cyclic AMP-PDE from crude homogenates of isolated fat cells from exercise trained animals may account for the decreased intracellular levels of cyclic AMP following catecholamine stimulation of isolated fat cells from trained rats.

Effect of amitriptyline on lipolysis and cyclic AMP concentration in isolated fat cells

Metabolism ◽  
1972 ◽  
Vol 21 (3) ◽  
pp. 223-229 ◽  
Author(s):  
Fred C. Lovrien ◽  
Ann A. Steele ◽  
Joseph D. Brown ◽  
Daniel B. Stone
Keyword(s):  
Cyclic Amp ◽  
Fat Cells ◽  
Isolated Fat Cells

Control of cyclic AMP levels in isolated fat cells from hamsters

1973 ◽  
Vol 304 (1) ◽  
pp. 188-196 ◽  
Author(s):  
K.J. Hittelman ◽  
C.F. Wu ◽  
R.W. Butcher
Keyword(s):  
Cyclic Amp ◽  
Fat Cells ◽  
Isolated Fat Cells

scholarly journals An effect of insulin on adipose-tissue adenosine 3′:5′-cyclic monophosphate phosphodiesterase

1970 ◽  
Vol 120 (1) ◽  
pp. 187-193 ◽  
Author(s):  
E. G. Loten ◽  
J. G. T. Sneyd
Keyword(s):  
Adipose Tissue ◽  
Cyclic Amp ◽  
Cyclic Nucleotide ◽  
Fat Cells ◽  
Maximal Velocity ◽  
Isolated Fat Cells ◽  
Phosphodiesterase Activity ◽  
Cyclic Monophosphate ◽  
Cyclic Nucleotide Phosphodiesterases ◽  
Fat Pads

1. 3′:5′-Cyclic nucleotide phosphodiesterase activity was measured in homogenates prepared from epididymal fat-pads and isolated fat-cells incubated in the absence and presence of insulin. 2. Homogenates of insulin-treated tissues showed an increase in phosphodiesterase activity compared with controls. No effect of insulin was observed when the hormone was added directly to homogenates. 3. There was kinetic evidence for the presence of two 3′:5′-cyclic nucleotide phosphodiesterases in adipose tissue. Insulin raised the maximal velocity of the low-Km enzyme and lowered the Km of the higher-Km enzyme. 4. It is suggested that the effect of insulin on adipose tissue phosphodiesterase accounts for the ability of this hormone to lower cyclic-AMP concentration in the tissue.

The Effect of Modifying the Combination of Insulin with Rat Adipose Cells on the Intracellular Levels of Cyclic Amp

1974 ◽  
Vol 46 (1) ◽  
pp. 75-87
Author(s):  
G. Jerums ◽  
D. J. Galton ◽  
C. Gilbert
Keyword(s):  
Plasma Membrane ◽  
Cyclic Amp ◽  
Insulin Receptor ◽  
Incubation Medium ◽  
Adrenergic Receptor ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Adipose Cells

1. Isoprenaline (1 μmol/l) and glucagon (1 μmol/l) raised the levels of cyclic AMP in isolated adipose cells of the rat to a maximum after incubation for approximately 15 min. 2. The effect of glucagon was impaired by pretreatment of adipose cells with trypsin (0.2 mg/ml and 2.0 mg/ml) and N-ethylmaleimide (5 mmol/l). The β-adrenergic receptor was insensitive to such forms of treatment. 3. Insulin (430 μunits/ml) lowered the intracellular levels of cyclic AMP in adipose cells stimulated with isoprenaline (1 μmol/l) and glucagon (1 μmol/l). This effect was observed after incubation for 5 min. 4. Pretreatment of cells with trypsin (0.2 mg/ml and 2.0 mg/ml) and N-ethylmaleimide (0.5 and 5 mmol/l) abolished the effect of insulin in decreasing the intracellular levels of cyclic AMP. At the higher concentration of trypsin a rise in intracellular levels of cyclic AMP was observed in the presence of insulin. 5. Similar concentrations of trypsin and N-ethylmaleimide decreased the disappearance of unlabelled insulin from the incubation medium and also decreased the binding of 125I-labelled insulin to isolated fat cells. 6. The effect of insulin on decreasing the intracellular levels of cyclic AMP in modified adipose cells significantly correlated with the disappearance of unlabelled insulin from the medium and with the percentage of total 125I-labelled insulin bound to cells. 7. The possibility is discussed of using the disappearance of insulin or binding of 125I-labelled insulin to adipose cells as a measure of insulin-receptor availability on the plasma membrane of fat-cells.

Lipolysis and cyclic AMP accumulation in isolated fat cells from chicks

1975 ◽  
Vol 26 (2) ◽  
pp. 243-247 ◽  
Author(s):  
Thomas A. Boyd ◽  
Paul B. Wieser ◽  
John N. Fain
Keyword(s):  
Cyclic Amp ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Cyclic Amp Accumulation
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