scholarly journals Triacylglycerol Lipase Activities of Cultured Rat L6 Myoblasts

1985 ◽  
Vol 38 (1) ◽  
pp. 41
Author(s):  
RK Tume ◽  
F D Shaw
Keyword(s):  
Lipoprotein Lipase ◽  
Cell Lines ◽  
Lipase Activity ◽  
Maximum Velocity ◽  
Acid Lipase ◽  
Ph Optimum ◽  
Triacylglycerol Lipase ◽  
Inhibitory Component ◽  
Cell Homogenate ◽  
Hydrolysis Of

The utilization of exogenous triacylglycerol by fusing and non-fusing rat L6 myoblasts grown in culture was investigated. Although small quantities of triacylglycerol were accumulated by both cell lines during an incubation of 2 h, no evidence could be found for the presence of lipoprotein lipase, either in the cells or released into the medium. Cell homogenate studies confirmed the absence of lipoprotein lipase but revealed the presence of an acid lipase having a pH optimum at 4�6. Acid lipase activity was mainly associated with a 15 000 g pellet and was capable of hydrolysing triolein at maximum velocity in the millimolar range. Unlike lipoprotein lipase, acid lipase was strongly inhibited by serum and preliminary investigations suggest that the inhibitory component of serum is located amongst the higher density lipoproteins. It is likely that the acid lipase is of lysosomal origin and is responsible for the hydrolysis of internalized triacylglycerol for subsequent utilization by the cell.

Methylamine does not inhibit rates of endogenous lipolysis in isolated myocardial cells from rat heart

1987 ◽  
Vol 65 (2) ◽  
pp. 226-229 ◽  
Author(s):  
Albert Kryski Jr. ◽  
Terje S. Larsen ◽  
Ignasi Ramírez ◽  
David L. Severson
Keyword(s):  
Fatty Acids ◽  
Lipase Activity ◽  
Rat Heart ◽  
Diabetic Rat ◽  
Myocardial Cells ◽  
Acid Lipase ◽  
Ph Optimum ◽  
Triacylglycerol Lipase ◽  
Rat Hearts ◽  
Lysosomotropic Agent

Triacylglycerol lipase activity with a pH optimum of 5 was present in homogenates of myocardial cells from rat heart. Acid lipase activity was inhibited by serum, heparin, and increased ionic strength. Methylamine, a lysosomotropic agent, did not inhibit the basal or isoproterenol-stimulated rate of endogenous lipolysis as measured by glycerol output from control myocytes. Similarly, accelerated rates of glycerol output that are a consequence of an elevation in the intracellular stores of triacylglycerols in myocytes from diabetic rat hearts and from myocytes prepared with free fatty acids in the isolation solutions were not reduced by methylamine. Therefore, the acid lysosomal triacylglycerol lipase must not be involved in the mobilization of endogenous triacylglycerols in myocardial cells from rat heart.

Characterization of the triacylglycerol lipase activity in three types of rat skeletal muscle

1987 ◽  
Vol 65 (3) ◽  
pp. 317-322 ◽  
Author(s):  
Wayne C. Miller ◽  
Warren K. Palmer ◽  
David A. Arnall ◽  
Lawrence B. Oscai
Keyword(s):  
Skeletal Muscle ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Lipolytic Activity ◽  
Vastus Lateralis ◽  
High Energy ◽  
Glycolytic Flux ◽  
Ph Optimum ◽  
Triacylglycerol Lipase ◽  
Triglyceride Lipase

The purpose of this study was to characterize the lipolytic activity of the alkaline triglyceride lipase in homogenates of three types of skeletal muscle obtained from heparin-perfused rat hindlimb. Specifically, the red portion of the vastus lateralis, the white portion of the vastus lateralis, and the soleus muscles were examined. To remove capillary-bound lipoprotein lipase from the capillary beds, muscle was perfused with an erythrocyte-free buffer containing 4% albumin, 5 units of heparin/mL, and 7.5 μM adenosine. Adenosine reduced perfusion pressure from 117 ± 5 to 86 ± 6 mmHg (1 mmHg = 133.32 Pa), providing evidence for an effective vasodilation. This vasodilation increased the amount of lipoprotein lipase removed from the capillary beds. By the end of the experiment, perfusates were lipoprotein lipase-free. Oxygen supply to the perfused hindlimb appeared adequate as evidenced by similar high energy phosphate values for perfused and contralateral control tissues. For example, in soleus muscle, ATP content was 4.5 ± 0.6 vs. 4.2 ± 0.3 μmol/g, ADP concentration was 1.0 ± 0.2 vs. 1.4 ± 0.2 μmol/g, and creatine phosphate level was 12.9 ± 0.7 vs. 11.0 ± 0.6 μmol/g for perfused and contralateral control soleus, respectively. In addition, K+ output by the hindlimb was negligible, while glycolytic flux of perfused muscle was similar to that measured in control tissue. The findings that triglyceride levels of soleus and red vastus lateralis were decreased suggest that endogenous triglyceride was providing energy for the hindlimb during perfusion. Skeletal muscle triglyceride lipase activity was stimulated by serum and heparin, inhibited by NaCl and protamine, and had a pH optimum of 8.1. These results are consistent with the hypothesis that the major lipolytic activity present in the intracellular compartment of skeletal muscle is the alkaline triglyceride lipase with characteristics similar to those of lipoprotein lipase.

Dibutyryl cAMP-induced Increases in triacylglycerol lipase activity in developing L8 myotube cultures

1990 ◽  
Vol 68 (6) ◽  
pp. 689-693 ◽  
Author(s):  
Warren K. Palmer ◽  
Lawrence B. Oscai ◽  
Peter J. Bechtel ◽  
Glenn A. Fisher
Keyword(s):  
Enzyme Activity ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Culture Medium ◽  
Cultured Cells ◽  
Muscle Cells ◽  
Cell Types ◽  
Dibutyryl Camp ◽  
Ph Optimum ◽  
Triacylglycerol Lipase

Triacylglycerol (TG) lipase activity, with an alkaline pH optimum, has been identified in the cellular fraction of L8 myotube cultures. This TG lipase activity was stimulated by serum and inhibited by NaCl and protamine sulfate. These characteristics have been classically described for lipoprotein lipase. It was possible to increase the activity of this TG lipase three- to fivefold by incubating the cells with dibutyryl cAMP Maximal enzyme activity was observed 16 h following the addition of 10–100 μM dibutyryl cAMP to the cultured cells. Enzyme activity returned to control levels 24 h after removal of the nucleotide from the culture medium. Serum-sensitive alkaline TG lipase activity was also identified in five other myotube preparations of cultured muscle cells. The highest levels of activity were found in rat skeletal muscle primary, H9, and L6 cell types. The finding that dibutyryl cAMP is an effective inducer of alkaline TG lipase activity provides us with a valuable model to investigate mechanisms regulating synthesis, compartmentalization, and transport of lipoprotein lipase in muscle.Key words: lipoprotein lipase, cultured muscle cells, enzyme induction.

Heparin-released lipolytic and esterolytic activities of human and rabbit plasmas

1961 ◽  
Vol 201 (5) ◽  
pp. 915-922 ◽  
Author(s):  
B. Shore ◽  
V. Shore
Keyword(s):  
Fatty Acids ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Ethyl Esters ◽  
Lipoprotein Lipase Activity ◽  
Hydrolysis Of

The enzymes released into both human and rabbit plasmas by heparin injection hydrolyzed, in addition to triglyceride moieties of lipoproteins, a number of mono- and diglycerides of C16 and C18 fatty acids after in vitro addition of the unemulsified glycerides to the plasma. In human postheparin plasma, these enzymes also hydrolyzed glycerides of butyric and caproic acids. The pure triglycerides and methyl or ethyl esters of C16 and C18 fatty acids were not substrates. The heparin-released activities for the hydrolysis of glycerides added in vitro persisted after all activity for the lipolysis of lipoproteins had been destroyed by heat. These activities also differed from lipoprotein lipase activity with respect to the effects of 1 m NaCl, dialysis, and aging the plasma at 4 C. It appears that heparin releases into the blood more than one enzyme or more than one form of an enzyme which may be involved in a stepwise degradation to fatty acids and glycerol of the triglyceride moieties of lipoproteins of density less than 1.007 g/ml.

The lipase activity of a partially purified lipolytic enzyme of Escherichia coli

1978 ◽  
Vol 56 (5) ◽  
pp. 324-328 ◽  
Author(s):  
G. Nantel ◽  
Georgia Baraff ◽  
P. Proulx
Keyword(s):  
Escherichia Coli ◽  
Lipase Activity ◽  
Slow Rate ◽  
Water Soluble ◽  
Lipolytic Enzyme ◽  
Ph Optimum ◽  
Chain Acyl ◽  
Marked Preference ◽  
Hydrolysis Of ◽  
Long Chain

Escherichia coli lipase was found to have a broad pH optimum between pH 8 and 10. Long-chain acyl triacylglycerols such as trioleoylglycerol were hydrolysed at a relatively slow rate, whereas, the shorter-chain acyl derivative tricapryloylglycerol was not. Triacylglycerols and diacylglycerols were broken down at a rate 10- to 15-fold greater than that for monoacylglycerol. Simple esters such as methyloieate and cetylpalmitate were hydrolysed at rates greater than that of triacylglycerol. Water-soluble esters such as p-nitrophenylacetate were not attacked. Hydrolysis of lipase substrates occurred more readily in the presence of an anionic detergent such as taurocholate. The enzyme had no marked preference for the 1- or 3-position of triacylglycerols but attacked these positions much more readily than position 2. The enzyme also catalyzed transacylation reactions with simple alcohols such as methanol or ethanol.

Lipoprotein lipase activity in human heart

1963 ◽  
Vol 205 (2) ◽  
pp. 401-404 ◽  
Author(s):  
J. David Schnatz ◽  
John W. Ormsby ◽  
Robert H. Williams
Keyword(s):  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Human Heart ◽  
Ammonium Hydroxide ◽  
Cottonseed Oil ◽  
Heart Tissue ◽  
Lipoprotein Lipase Activity ◽  
Oil Emulsion ◽  
Ventricular Tissue ◽  
Hydrolysis Of

Human ventricular tissue was obtained 11–28 hr post mortem, homogenized in ammonium hydroxide, and tested for its ability to catalyze the hydrolysis of an "activated" cottonseed oil emulsion. Lipolysis, as indicated by a rise in fatty acids, occurred in the presence of a freshly prepared homogenate, but not in the presence of a boiled homogenate. Sodium chloride, 1 m, inhibited the reaction, but sodium fluoride, 0.2 m, did not. An activated cottonseed oil emulsion was more readily hydrolyzed than a "nonactivated" cottonseed oil emulsion. Approximately 50% of the activity of the homogenate sedimented at a gravitational force produced by centrifugation at 800 g for 10 min. The conclusion is that human heart tissue, like animal heart, contains lipoprotein lipase activity and that this activity is associated, in part, with the heavier cellular particles.

scholarly journals The inhibition in vivo of lipoprotein lipase (clearing-factor lipase) activity by triton WR-1339

1976 ◽  
Vol 156 (3) ◽  
pp. 539-543 ◽  
Author(s):  
J Borensztajn ◽  
M S Rone ◽  
T J Kotlar
Keyword(s):  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Lipoprotein Lipase Activity ◽  
Rat Hearts ◽  
Maximum Inhibition ◽  
Triton Wr 1339 ◽  
Perfused Rat Hearts ◽  
Hydrolysis Of ◽  
Isolated Perfused Rat Hearts

1. Lipoprotein lipase activity was measured in heart homogenates and in heparin-releasable and non-releasable fractions of isolated perfused rat hearts, after the intravenous injection of Triton WR-1339. 2. In homogenates of hearts from starved, rats, lipoprotein lipase activity was significantly inhibited (P less than 0.001) 2h after the injection of Triton. This inhibition was restricted exclusively to the heparin-releasable fraction. Maximum inhibition occurred 30 min after the injection and corresponded to about 60% of the lipoprotein lipase activity that could be released from the heart during 30 s perfusion with heparin. 3. Hearts of Triton-treated starved rats were unable to take up and utilize 14C-labelled chylomicron triacylglycerol fatty acids, even though about 40% of heparin-releasable activity remained in the hearts. 4. It is concluded that Triton selectively inhibits the functional lipoprotein lipase, i.e. the enzyme directly involved in the hydrolysis of circulating plasma triacylglycerols. 5. Lipoprotein lipase activities measured in homogenates of soleus muscle of starved rats and adipose tissue of fed rats were decreased by 25 and 39% respectively after Triton injection. It is concluded that, by analogy with the heart, these Triton-inhibitable activities correspond to the functional lipoprotein lipase.

scholarly journals Effect of diabetes on acid and neutral triacylglycerol lipase and on lipoprotein lipase activities in isolated myocardial cells from rat heart

1986 ◽  
Vol 238 (1) ◽  
pp. 233-238 ◽  
Author(s):  
I Ramírez ◽  
D L Severson
Keyword(s):  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Specific Activity ◽  
Subcellular Fractions ◽  
Capillary Endothelium ◽  
Myocardial Cells ◽  
Protamine Sulphate ◽  
Triacylglycerol Lipase ◽  
Neutral Lipase ◽  
High Concentrations

A neutral triacylglycerol lipase activity that is separate and distinct from lipoprotein lipase (LPL) could be measured in homogenates of myocardial cells if protamine sulphate and high concentrations of albumin were included in the assay. This neutral lipase was predominantly particulate, with the highest relative specific activity in microsomal subcellular fractions. The induction of diabetes by the administration of streptozotocin to rats resulted in a decrease in LPL activity in myocyte homogenates and in particulate subcellular fractions, but the percentage of cellular LPL activity that was released during incubation of myocytes with heparin was normal. In contrast, neutral lipase activity was increased in diabetic myocyte homogenates and microsomal fractions. Acid triacylglycerol lipase activity was not changed in diabetic myocytes. The decrease in LPL in myocytes owing to diabetes may result in the decreased functional LPL activity at the capillary endothelium of the diabetic heart.

Expression of lipoprotein lipase during differentiation of cultured L6 muscle cells

1994 ◽  
Vol 72 (3) ◽  
pp. 243-247 ◽  
Author(s):  
Mary Jo LaDu ◽  
Warren K. Palmer
Keyword(s):  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Time Course ◽  
Muscle Cells ◽  
Alkaline Ph ◽  
Ph Optimum ◽  
L6 Cells ◽  
Highly Correlated ◽  
L6 Muscle Cells

The presence of lipoprotein lipase (LPL) in L6 muscle cells is equivocal. Analysis of a 21-day time course indicates that these cells express both LPL activity and mRNA. Lipase activity peaked at 4 days after plating and decreased to a nadir at day 21 after plating. Characterization of lipase activity at 4 and 19 days after plating, corresponding to myoblasts and myotubes, respectively, indicated that most of the enzyme activity had the properties of LPL, including an alkaline pH optimum, a serum requirement, and inhibition by NaCl. LPL mRNA expression peaked at 7 days after plating and fell slightly (24%) at day 21. The primary LPL mRNA species in these cells is 3.7 kb in length. Lipase activity and LPL mRNA were highly correlated during the time course (r = +0.82), suggesting transcriptional regulation of the enzyme. These data clearly demonstrate that L6 cells express LPL during differentiation.Key words: myoblasts, myotubes, mRNA, total protein, total RNA.

Diacylglycerol lipase and kinase activities in rabbit aorta and coronary microvessels

1986 ◽  
Vol 64 (10) ◽  
pp. 976-983 ◽  
Author(s):  
David L. Severson ◽  
Mariette Hee-Cheong
Keyword(s):  
Fatty Acid ◽  
Lipase Activity ◽  
Kinase Activity ◽  
Rabbit Aorta ◽  
Monoacylglycerol Lipase ◽  
Ph Optimum ◽  
Diacylglycerol Lipase ◽  
Dependent Protein ◽  
Hydrolysis Of ◽  
Hydrolysis Activity

Diacylglycerol lipase and kinase activities were measured in particulate and soluble fractions from rabbit aorta (intima–media) and coronary microvessels. With rabbit aorta, the hydrolysis at the sn-1 position of 1-palmitoyl-2-oleoyl-sn-glycerol had a pH optimum of 5–6 and was greater than hydrolysis at the sn-2 position (pH optimum of 6.5). Only the 2-monoacylglycerol accumulated during incubations at pH 5 and 6.5. These results are consistent with an ordered two-step reaction sequence where the fatty acid at the sn-1 position is released first, followed by the hydrolysis of the fatty acid from the 2-monoacylglycerol by a monoacylglycerol lipase with a neutral pH optimum. Lipase activity (sn-2 hydrolysis) at pH 6.5 was greater than kinase activity at all substrate concentrations. The presence of arachidonate at the sn-2 position of the diacylglycerol increased kinase activity but had little effect on lipase activity. Kinase activity was mainly particulate, whereas 50–60% of diacylglycerol lipase and 50% of monoacylglycerol lipase activity were soluble. Diacylglycerol lipase and kinase were also present in coronary microvessel preparations. Diacylglycerol lipase (sn-2 hydrolysis) activity in coronary microvessels was not enhanced by preincubation of the enzyme preparation with cAMP-dependent protein kinase.

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