Lipolysis in isolated myocardial cells from diabetic rat hearts

1985 ◽  
Vol 249 (5) ◽  
pp. H1024-H1030 ◽  
Author(s):  
K. A. Kenno ◽  
D. L. Severson
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
Diabetic Rat ◽  
Myocardial Cells ◽  
Atp Content ◽  
Intracellular Accumulation ◽  
Rat Hearts ◽  
Triacylglycerol Content ◽  
Release Of Glycerol ◽  
Stimulation Of

Diabetes in rats was induced with streptozotocin (100 mg/kg); myocardial cells (myocytes) were isolated from the hearts 3-4 days later. Diabetic myocytes were characterized as having the same viability and ATP content as control myocytes, but the yield was reduced. The triacylglycerol content of diabetic myocytes was elevated by 3.7-fold; this resulted in an increased rate of glycerol output during subsequent incubations. There was a stoichiometric relationship between the decline in the cellular triacylglycerol content and the release of glycerol into the incubation medium. Isoproterenol stimulated the output of glycerol from control myocytes by about twofold, but the stimulation of glycerol output from diabetic myocytes by isoproterenol was markedly less. The combination of 1-methyl-3-isobutylxanthine with isoproterenol or 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate also failed to produce the same lipolytic response in diabetic myocytes as in control myocytes. Triacylglycerol-loaded myocytes from control rats, prepared by including palmitate in the isolation buffers, were also characterized as having increased basal rates of glycerol output and a reduced lipolytic response to isoproterenol. The level of free fatty acids in diabetic myocytes was 2.8-fold greater than in myocytes from control hearts. The intracellular accumulation of free fatty acids in these quiescent populations of diabetic myocytes may limit the ability of catecholamines to produce a further stimulation of lipolysis.

Stimulation of lipolysis in rat heart myocytes by isoproterenol

1985 ◽  
Vol 248 (2) ◽  
pp. H208-H216 ◽  
Author(s):  
A. Kryski ◽  
K. A. Kenno ◽  
D. L. Severson
Keyword(s):  
Phosphodiesterase Inhibitor ◽  
Myocardial Cells ◽  
Cyclic Monophosphate ◽  
Rat Hearts ◽  
Triacylglycerol Content ◽  
Rat Heart Myocytes ◽  
Dose Dependent Increase ◽  
Release Of Glycerol ◽  
Dose Dependent ◽  
Stimulation Of

Calcium-tolerant myocytes were isolated from rat hearts. Isoproterenol produced a dose-dependent increase in glycerol output (lipolysis) that could be blocked by propranolol. The presence of glucose in the incubation medium enhanced the release of glycerol from myocytes but had no effect on the decline in triacylglycerol content. No incorporation of radioactivity from [U-14C]glucose into glycerol could be detected. In incubations with isoproterenol, there was a stoichiometric relationship between the glycerol output and the decrease in triacylglycerol levels. The addition of the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine resulted in an increase in the basal glycerol output and an enhancement of the isoproterenol-stimulated lipolytic rate. Forskolin and 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate also produced a concentration-dependent stimulation of lipolysis in myocytes. Therefore, lipolysis in isolated myocytes must be regulated by adenosine 3',5'-cyclic monophosphate-dependent mechanisms. These results demonstrate that lipolysis can be observed in myocardial cells and that the lipolytic response to isoproterenol cannot be secondary to a physiological (inotropic) response since these myocyte preparations are quiescent.

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.

scholarly journals The regulation of glyceride synthesis in isolated white-fat cells. The effects of palmitate and lipolytic agents

1972 ◽  
Vol 128 (5) ◽  
pp. 1057-1067 ◽  
Author(s):  
E. D Saggerson
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Free Fatty Acids ◽  
Fatty Acid Synthesis ◽  
Acid Synthesis ◽  
Fat Cells ◽  
Glyceride Synthesis ◽  
Glucose Incorporation ◽  
High Concentrations ◽  
Stimulation Of

1. 0.5mm-Palmitate stimulated incorporation of [U-14C]glucose into glyceride glycerol and fatty acids in normal fat cells in a manner dependent upon the glucose concentration. 2. In the presence of insulin the incorporation of 5mm-glucose into glyceride fatty acids was increased by concentrations of palmitate, adrenaline and 6-N-2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate up to 0.5mm, 0.5μm and 0.5mm respectively. Higher concentrations of these agents produced progressive decreases in the rate of glucose incorporation into fatty acids. 3. The effects of palmitate and lipolytic agents upon the measured parameters of glucose utilization were similar, suggesting that the effects of lipolytic agents are mediated through increased concentrations of free fatty acids. 4. In fat cells from 24h-starved rats, maximal stimulation of glucose incorporation into fatty acids was achieved with 0.25mm-palmitate. Higher concentrations of palmitate were inhibitory. In fat cells from 72h-starved rats, palmitate only stimulated glucose incorporation into fatty acids at high concentrations of palmitate (1mm and above). 5. The ability of fat cells to incorporate glucose into glyceride glycerol in the presence of palmitate decreased with increasing periods of starvation. 6. It is suggested that low concentrations of free fatty acids stimulate fatty acid synthesis from glucose by increasing the utilization of ATP and cytoplasmic NADH for esterification of these free fatty acids. When esterification of free fatty acids does not keep pace with their provision, inhibition of fatty acid synthesis occurs. Provision of free fatty acids far in excess of the esterification capacity of the cells leads to uncoupling of oxidative phosphorylation and a secondary stimulation of fatty acid synthesis from glucose.

Regulation of lysophosphatidylcholine-metabolizing enzymes in isolated myocardial cells from rat heart

1985 ◽  
Vol 63 (8) ◽  
pp. 944-951 ◽  
Author(s):  
David L. Severson ◽  
Thea Fletcher
Keyword(s):  
Fatty Acids ◽  
Palmitic Acid ◽  
Free Fatty Acids ◽  
Rat Heart ◽  
Marked Reduction ◽  
Myocardial Cells ◽  
Acyltransferase Activity ◽  
Metabolizing Enzymes ◽  
Enzymatic Pathways ◽  
Lysophospholipase Activity

Enzymatic pathways involved in the metabolism of lysophosphatidylcholine were investigated in rat heart myocardial cells. Acyl CoA-dependent acyltransferase activity was localized in microsomes, and was much greater than lysophospholipase activity in either cytosolic or microsomal fractions. The cytosolic lysophospholipase was more sensitive to inhibition by palmitylcarnitine in comparison to free fatty acids. In contrast, free fatty acids (oleate and palmitate) produced a greater inhibition of the microsomal acyltransferase and lysophospholipase than did palmitylcarnitine. A reduction in the assay pH to 6.5 resulted in an increase in microsomal acyltransferase and cytosolic lysophospholipase activities, but brought about a marked reduction in the microsomal lysophospholipase activity. At pH 6.5, the percentage inhibition of the microsomal acyltransferase by palmitylcarnitine was reduced, whereas the inhibition by palmitic acid was enhanced. The inhibition of the microsomal lysophospholipase by both palmitylcarnitine and palmitic acid was reduced at pH 6.5. With respect to myocardial ischemia, the inhibition of microsomal acyltransferase by free fatty acids and the reduction in microsomal lysophospholipase activity due to acidosis may contribute to the elevation of cellular lysophosphoglycerides which are arrhythmogenic.

scholarly journals Protective Effect of Amiloride Against Reperfusion Damage as Evidenced by Inhibition of Accumulation of Free Fatty Acids in Working Rat Hearts

1997 ◽  
Vol 61 (12) ◽  
pp. 1021-1029 ◽  
Author(s):  
Yoshihisa Nasa ◽  
A. N. Ehsanul Hoque ◽  
Kazuo Ishihara ◽  
Hiroko Hashizume ◽  
Yasushi Abiko
Keyword(s):  
Fatty Acids ◽  
Protective Effect ◽  
Free Fatty Acids ◽  
Reperfusion Damage ◽  
Rat Hearts

Lipid and glycogen metabolism in the hypoxic heart: effects of epinephrine

1975 ◽  
Vol 229 (4) ◽  
pp. 885-889 ◽  
Author(s):  
Crass MF ◽  
GM Pieper
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Free Fatty Acids ◽  
Fatty Acid Oxidation ◽  
Glycogen Metabolism ◽  
Acid Oxidation ◽  
Triglyceride Fatty Acid ◽  
Rat Hearts ◽  
Perfused Rat Hearts

The metabolism of cardiac lipids and glycogen in hypoxic and well-oxygenated perfused rat hearts was studied in the presence or absence of epinephrine. Heart lipids were pre-labeled in vivo with [1-14C]palmitate. Triglyceride disappearance (measured chemically and radiochemically) was observed in well-oxygenated hearts and was stimulated by epinephrine (4.1 X 10(-7)M). Utilization of tissue triglycerides was inhibited in hypoxic hearts in the presence or absence of added epinephrine. Hypoxia resulted in a small increase in tissue 14C-free fatty acids and inhibition of 14C-labeled triglyceride fatty acid oxidation. Epinephrine had no stimulatory effect on fatty acid oxidation in hypoxic hearts. Utilization of 14C-labeled phospholipids (and total phospholipids) was similar in well-oxygenated and hypoxic hearts with or without added epinephrine. These results suggested that the antilipolytic effects of hypoxia were predominant over the lipolytic effects of epinephrine. Glycogenolysis was stimulated threefold by epinephrine in well-oxygenated hearts. Hypoxia alone was a potent stimulus to glycogenolysis. Addition of epinephrine to perfusates of hypoxic hearts resulted in a slight enhancement of glycogenolysis.

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