THE EFFECT OF INCUBATION ON THE CHARACTERISTICS OF THE LIPOLYTIC ACTIVITY OF RAT ADIPOSE TISSUE

1962 ◽  
Vol 40 (6) ◽  
pp. 703-707 ◽  
Author(s):  
C. H. Hollenberg
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Phosphate Buffer ◽  
Lipolytic Activity ◽  
Serum Triglyceride ◽  
Fresh Tissue ◽  
Intact Tissue ◽  
Separate Type ◽  
Tissue Homogenates ◽  
Rat Adipose Tissue

A study has been made of the changes produced in the characteristics of the lipolytic activity of rat adipose tissue homogenates by prolonged preincubation of the intact tissue in phosphate buffer. Fresh tissue homogenates were markedly more active on a serum–triglyceride medium (activated substrate) than on triglyceride alone while little difference was noted with homogenates of preincubated tissue. The activity of fresh tissue homogenates was increased by addition of heparin; homogenates of incubated tissue were not affected. Fresh tissue homogenates were inhibited to a greater extent by protamine than were preparations of incubated material. Addition of glucose and insulin to the buffer partially maintained the activity of incubated tissue on activated substrate. These results indicate that while lipolytic activity of fresh rat adipose tissue has characteristics similar to lipoprotein lipase, the activity of incubated tissue differs from this enzyme in several respects. This study demonstrates the lability of lipoprotein lipase in rat adipose tissue and suggests the presence in this tissue of a separate type of lipolytic activity.

THE EFFECT OF INCUBATION ON THE CHARACTERISTICS OF THE LIPOLYTIC ACTIVITY OF RAT ADIPOSE TISSUE

1962 ◽  
Vol 40 (1) ◽  
pp. 703-707
Author(s):  
C. H. Hollenberg
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Phosphate Buffer ◽  
Lipolytic Activity ◽  
Serum Triglyceride ◽  
Fresh Tissue ◽  
Intact Tissue ◽  
Separate Type ◽  
Tissue Homogenates ◽  
Rat Adipose Tissue

A study has been made of the changes produced in the characteristics of the lipolytic activity of rat adipose tissue homogenates by prolonged preincubation of the intact tissue in phosphate buffer. Fresh tissue homogenates were markedly more active on a serum–triglyceride medium (activated substrate) than on triglyceride alone while little difference was noted with homogenates of preincubated tissue. The activity of fresh tissue homogenates was increased by addition of heparin; homogenates of incubated tissue were not affected. Fresh tissue homogenates were inhibited to a greater extent by protamine than were preparations of incubated material. Addition of glucose and insulin to the buffer partially maintained the activity of incubated tissue on activated substrate. These results indicate that while lipolytic activity of fresh rat adipose tissue has characteristics similar to lipoprotein lipase, the activity of incubated tissue differs from this enzyme in several respects. This study demonstrates the lability of lipoprotein lipase in rat adipose tissue and suggests the presence in this tissue of a separate type of lipolytic activity.

Lipolytic action of epinephrine in adipose tissue homogenates

1964 ◽  
Vol 206 (1) ◽  
pp. 149-152 ◽  
Author(s):  
David Rubinstein ◽  
Sylvester Chiu ◽  
Jean Naylor ◽  
John C. Beck
Keyword(s):  
Growth Hormone ◽  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Lipolytic Activity ◽  
Supernatant Fraction ◽  
Lipid Layer ◽  
Lipolytic Action ◽  
Tissue Homogenates ◽  
Stimulation Of

Incubation of intact adipose tissue with ACTH, certain preparations of growth hormone, and epinephrine induces an increase in lipolytic activity in homogenates prepared from this tissue. Epinephrine also causes an increase in lipolytic activity when added directly to adipose tissue homogenates. The increase is inhibited by 4 x 10–4 m iodoacetate. Mitochondrial and "supernatant" fractions (including microsomes) and the lipid layer all possess lipase activity, but only the lipase found in the supernatant fraction can be activated by epinephrine. Protamine activates this lipase; addition of epinephrine has no additive effect. Heparin inhibits the stimulation of lipase activity by epinephrine, but has no action on the lipolysis occurring in the absence of epinephrine. It is concluded that the epinephrine-stimulated lipase is distinct from lipoprotein lipase and the lipase present in unstimulated tissue.

scholarly journals Increase in Lipoprotein Lipase Activity in Isolated Rat Adipose Tissue by Selenate.

1993 ◽  
Vol 16 (1) ◽  
pp. 6-10 ◽  
Author(s):  
Hiroshi UEKI ◽  
Yusuke OHKURA ◽  
Toshio MOTOYASHIKI ◽  
Nobuaki TOMINAGA ◽  
Tetsuo MORITA
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Lipoprotein Lipase Activity ◽  
Rat Adipose Tissue ◽  
Isolated Rat

Diurnal rhythms and effects of fasting and refeeding on rat adipose tissue lipoprotein lipase

1996 ◽  
Vol 271 (6) ◽  
pp. E1092-E1097 ◽  
Author(s):  
M. Bergo ◽  
G. Olivecrona ◽  
T. Olivecrona
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Specific Activity ◽  
Early Morning ◽  
Diurnal Rhythms ◽  
Mrna Levels ◽  
Short Term ◽  
Early Afternoon ◽  
Rat Adipose Tissue ◽  
Adipose Tissue Lipoprotein Lipase

The activity of lipoprotein lipase (LPL) in adipose tissue is modulated by changes in the nutritional status. We have measured LPL activity, mass, and mRNA levels in rat adipose tissue during normal feeding cycles, during short- and long-term fasting, and during refeeding after fasting. LPL activity displayed a diurnal rhythm. The activity was highest during the night and early morning, decreased to a minimum during the early afternoon, and then increased again. These changes corresponded to the feeding pattern. The increases and/or decreases resulted from changes in LPL synthetic rate compounded by posttranslational mechanisms. During short-term fasting, LPL specific activity decreased to < 30% of control. The specific activity was restored within 4 h by refeeding. On longer fasting, LPL mRNA decreased. This became significant from 36 h. On refeeding, it took 12 h to restore the mRNA levels, whereas tissue LPL activity and mass could not be fully restored by 36 h of refeeding. These data show that LPL activity during short-term fasting is regulated posttranscriptionally, which allows for quick upregulation after refeeding. On longer fasting, other mechanisms affecting LPL transcription and synthesis come into play, and upregulation after refeeding is slowed down.

Factors Affecting the Inactivation of Insulin-125I by Rat Adipose Tissue

1971 ◽  
Vol 49 (5) ◽  
pp. 457-463 ◽  
Author(s):  
Alfred Fessler ◽  
Bernard Rubinstein ◽  
David Rubinstein ◽  
John C. Beck
Keyword(s):  
Adipose Tissue ◽  
Free Fraction ◽  
Tissue Homogenate ◽  
Immunoreactive Insulin ◽  
Insulin Degradation ◽  
Factors Affecting ◽  
Free Iodine ◽  
Tissue Homogenates ◽  
Rat Adipose Tissue ◽  
Tissue Fraction

The degradation of insulin-125I by adipose tissue was determined by the appearance of 125I in the trichloroacetic acid (TCA) soluble tissue fraction. A maximum of 30% of the 125I appears as TCA-soluble material following incubation with adipose tissue homogenates. Destruction of immunoreactive insulin and insulin-like activities is, however, complete. The appearance of TCA-soluble 125I is due to proteolysis rather than to deiodination since it can be decreased by the addition of unlabelled insulin to the incubation mixture. No increase in free iodine could be detected. The degradation of insulin by intact adipose tissue is greater than by free adipocytes. Tissue homogenization greatly increases the rate of insulin degradation. Most of the insulin-degrading activity is found in the "fat-free" fraction of the tissue homogenate, but this activity is rapidly lost during incubation at 37 °C. In contrast the lesser activity in the fat layer remains stable at 37°. N-Ethylmaleimide, which inhibits breakdown of the hormone by homogenates, increases the degradation of insulin by adipocytes. These results indicate that caution must be employed in interpreting binding and destruction of iodinated insulin and raise the possibility that insulin may penetrate the cell prior to its destruction.

scholarly journals Effects of glucose and insulin on the activation of lipoprotin lipase and on protein-synthesis in rat adipose tissue

1980 ◽  
Vol 188 (1) ◽  
pp. 193-199 ◽  
Author(s):  
S M Parkin ◽  
K Walker ◽  
P Ashby ◽  
D S Robinson
Keyword(s):  
Protein Synthesis ◽  
Enzyme Activity ◽  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Specific Activity ◽  
The Other ◽  
Lipoprotein Lipase Activity ◽  
Fat Bodies ◽  
Rat Adipose Tissue ◽  
Adipose Tissue Lipoprotein Lipase

Glucose, and certain sugars that can readily be converted to glucose 6-phosphate, bring about an activation of adipose-tissue lipoprotein lipase when epididymal fat-bodies from starved rats are incubated in the presence of cycloheximide. Other substrates do not support the activation. If the tissue is preincubated in the presence of cycloheximide for longer than 2h, the ability of added glucose to activate the enzyme is lost. On the other hand, the addition of glucose still brings about an increase in lipoprotein lipase activity after preincubation in the absence of cycloheximide for as long as 4h. The magnitude of the increase in enzyme activity brought about by the addition of glucose is increased when protein synthesis is stimulated during the preincubation period by insulin. The results are interpreted in terms of the existence in adipose tissue of a proenzyme pool of lipoprotein lipase that is normally maintained by protein synthesis and that is converted to complete enzyme of higher specific activity by a process that specifically requires glucose.

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