Utilization of fatty acids by rat liver slices as a function of medium concentration

1964 ◽  
Vol 206 (2) ◽  
pp. 345-350 ◽  
Author(s):  
Herbert Rose ◽  
Martha Vaughan ◽  
Daniel Steinberg
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Rat Liver ◽  
Neutral Lipids ◽  
Specific Radioactivity ◽  
Lipid Synthesis ◽  
Normal Liver ◽  
Precursor Pool ◽  
Liver Slices

The rate of incorporation of palmitate-1-C14 into neutral lipids and phospholipids of rat liver slices in vitro and its conversion to C14O2 were shown to increase markedly as the free fatty acid (FFA) concentration of the medium was increased. Incorporation into lipids and conversion to C14O2 proceeded linearly with time over 60 min. The incorporation of glycerol-1,3-C14 into neutral lipids also increased as the FFA concentration of the medium was increased but incorporation into phospholipids was unchanged. It is concluded that high FFA concentrations cause a true increase in rate of neutral lipid synthesis by liver slices. The associated increase in incorporation of labeled palmitate into phospholipids most likely reflects the higher specific radioactivity of the precursor pool of FFA and/or an exchange reaction rather than a true increase in net synthesis. A method for recovering tissue FFA quantitatively is described. Normal liver was found to contain 0.40–0.87 µEq FFA/g wet wt. The composition of this tissue FFA fraction is presented.

EFFECTS OF HYPOGLYCIN A ON THE METABOLISM OF AMINO ACIDS BY LIVER SLICES

1964 ◽  
Vol 42 (1) ◽  
pp. 139-142 ◽  
Author(s):  
S. J. Patrick ◽  
L. C. Stewart
Keyword(s):  
Amino Acids ◽  
Fatty Acids ◽  
Fatty Acid ◽  
Glutamic Acid ◽  
Rat Liver ◽  
Inhibitory Effects ◽  
Liver Slices

The effects of hypoglycin A on the metabolism of L-leucine-C14, L-alanine-C14, and L-glutamic-acid-C14 by rat liver slices have been investigated. Hypoglycin exerted markedly inhibitory effects on the conversion of leucine-C14 to fatty acid, cholesterol, and CO2. Conversion of alanine-C14 and glutamic acid-C14 to fatty acids was also inhibited by hypoglycin. No effects of hypoglycin on the conversion of C14-amino acids into protein or glycogen were demonstrated.

Fatty Acid Utilization by Adrenalectomized Rats

1956 ◽  
Vol 186 (2) ◽  
pp. 190-192 ◽  
Author(s):  
W. F. Perry ◽  
Helen F. Bowen
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Octanoic Acid ◽  
Hepatic Lipogenesis ◽  
Acetoacetic Acid ◽  
Fatty Acid Utilization ◽  
Liver Slices ◽  
Adrenalectomized Rats

The production of radioactive CO2 by intact and adrenalectomized rats given 1 C14 octanoic acid and the production of radioactive CO2 and radioactive acetoacetic acid by surviving liver slices from adrenalectomized and unoperated rats using 1 C14 octanoic acid as substrate have been studied. It was found that the CO2 production and acetoacetic acid production in vitro and CO2 production in vivo did not differ in the two types of animals. These results suggest that the adrenalectomized rat does not utilize fatty acids at a higher than normal rate and that the previously reported decreased incorporation of acetate into fatty acids by the liver slices from adrenalectomized rats is a reflection of decreased hepatic lipogenesis.

Effect of Adrenalectomy on the Incorporation of Acetate Into Fatty Acids, Cholesterol and Acetoacetic Acid by Rat Liver Slices

1955 ◽  
Vol 184 (1) ◽  
pp. 59-62 ◽  
Author(s):  
W. F. Perry ◽  
Helen F. Bowen
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Rat Liver ◽  
Acid Formation ◽  
Acetoacetic Acid ◽  
Adrenalectomized Animal ◽  
Liver Slices ◽  
Adrenalectomized Rats

The incorporation of C14 acetate into fatty acids, cholesterol, acetoacetic acid and CO2 by liver slices of intact and adrenalectomized rats was studied, the slices being incubated in bicarbonate and phosphate buffers. It was found that in both buffer systems incorporation into fatty acids and cholesterol was depressed while incorporation into acetoacetic acid was unaffected by adrenalectomy. However, total acetoacetic acid formation by the slices tended to be higher in preparations from adrenalectomized animals. The amount of acetate carbon appearing as CO2 was similar with slices from both types of animals. Bicarbonate was found to be a more favorable medium than PO4 for fatty acid formation, while PO4 was the more favorable medium for cholesterogenesis, though the differences between adrenalectomized and intact animals persisted in either buffer. Forced feeding with glucose increased the incorporation of acetate into fat and cholesterol in both buffer systems in adrenalectomized as well as in intact animals. However, the adrenalectomized preparation still incorporated acetate to a lesser extent than the controls. It was concluded that while the depressed incorporation of acetate into fatty acid and cholesterol by adrenalectomized liver slices was consistent with a depressed synthesis of these lipids, there was also the possibility that it reflected an increased turnover of lipids in the liver of the adrenalectomized animal.

The metabolism of the erythrocyte. XIX. Factors affecting esterification of linoleate by human erythrocytes

1969 ◽  
Vol 47 (10) ◽  
pp. 967-975 ◽  
Author(s):  
Kamini Shastri ◽  
David Rubinstein
Keyword(s):  
Fatty Acid ◽  
Cell Population ◽  
Neutral Lipids ◽  
Phthalate Esters ◽  
Ringer Solution ◽  
Human Erythrocytes ◽  
Phosphate Level ◽  
Factors Affecting ◽  
Precursor Pool

Factors affecting the esterification in vitro of linoleate-1-14C by intact human erythrocytes were investigated. Lecithin contained the highest proportion of the esterified fatty acid, but it was not possible to detect any incorporation into the neutral lipids. Glucose caused a slight increase in incorporation into erythrocytes which had been stored for 18 h at 4°, but had little effect on fresh cells. Esterification was proportional to the intracellular nucleotide labile phosphate level (corresponding to the ATP and ADP levels), provided the latter was less than that found in fresh erythrocytes. However, no further increase in esterification occurred when the level of nucleotide labile phosphate was raised to twice that of fresh cells by incubation for 10 h with glucose and adenine. Water-immiscible phthalate esters, used for the separation of young and old erythrocytes, increased esterification two- to three-fold without altering either its correlation with the intracellular nucleotide labile phosphate level or the distribution of the linoleate-1-14C among the various phospholipids. The oldest 5% of the cell population, whether separated by phthalate esters or in Ringer solution, showed a diminished level of nucleotide labile phosphate and a decreased rate of esterification. The presence of glucose restored the level of linoleate-1-14C incorporation by old cells to that of the remainder of the cell population. Lysolecithin increased the rate of esterification without altering the distribution of the linoleate-14C among the phospholipids, and removed the difference between normal and energy-poor cells. These data suggest that the rate-limiting step in esterification may involve an energy-sensitive transport of free fatty acids into an intracellular precursor pool rather than the fatty acid esterification (thiokinase) reaction.

In Vitro Metabolism of Fatty Acids by Adipose and Liver Tissue of the Adrenalectomized Rat

1957 ◽  
Vol 189 (3) ◽  
pp. 433-436 ◽  
Author(s):  
W. F. Perry ◽  
Helen F. Bowen
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Octanoic Acid ◽  
Normal Liver ◽  
Liver Slice ◽  
Acetate Incorporation ◽  
Slice Preparation ◽  
Progressive Loss ◽  
Liver Slices

The utilization of acetate and octanoate by adipose tissue from rats 1 and 2 weeks postadrenalectomy has been studied. In addition, acetate incorporation into liver fatty acids and ketogenesis by liver slices from 2-week postoperative animals has been measured. Adrenalectomy resulted in a progressive loss of fat from adipose tissue. At 1-week postadrenalectomy the incorporation of acetate into fatty acids by adipose tissue did not differ from the control preparations but was much increased 2 weeks after adrenalectomy. At this time there was no increase in utilization of added octanoic acid by the adipose tissue and neither at 1 nor at 2 weeks was the production of CO2 from either acetate or octanoic significantly different from normal. Liver slices from 2-week adrenalectomized animals had a markedly defective ability to incorporate acetate into liver fatty acids similar to that previously noted in 1-week animals. However, liver slice preparation from 2-week adrenalectomized rats showed increased ketone body formation, indicating increased fatty acid utilization by the liver. It is suggested that there is a gradual mobilization of fat from the depots to the liver in the adrenalectomized rat with increased utilization of fat by the liver.

Uncoupling activity of endogenous free fatty acids in rat liver mitochondria

1978 ◽  
Vol 56 (2) ◽  
pp. 111-116 ◽  
Author(s):  
Samuel H. P. Chan ◽  
Edward Higgins Jr.
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Free Fatty Acid ◽  
Free Fatty Acids ◽  
Rat Liver ◽  
Respiratory Control ◽  
Aging Effect ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria

Changes in the respiratory control index (RCI) and ADP:O ratio were found to be related to alterations in the free fatty acids levels of rat liver mitochondria aging in 0.25 M sucrose–Tris buffer at 0 °C. Free fatty acid levels increased with time after isolation of mitochondria while a concomitant decrease in the RCI and ADP:O ratio occurred. The changes in free fatty acid levels corresponded with the reported increasing levels of phospholipase A activity in aged mitochondrial preparations. Washing these mitochondria with sucrose buffer containing 1% defatted bovine serum albumin (BSA) counteracted the aging effect on the RCI (e.g., 2.5 to 3.5) and reduced the free fatty acid levels (e.g., 50 to 16 nmol/mg protein). This reversible phenomenon could be repeated several times during the in vitro aging at 0 °C. Use of 125I-iodinated BSA showed that approximately 5 μg BSA/mg mitochondria was adsorbed by the mitochondrial membranes during washing. These results indicate a direct correlation between the level of endogenous fatty acids and the uncoupling of mitochondrial oxidative phosphorylation. The mechanism of counteracting the aging effect by BSA involves the removal of some of the free fatty acids.

scholarly journals Secretion and storage of newly synthesized hepatic triacylglycerol fatty acids in vivo in different nutritional states and in diabetes

1988 ◽  
Vol 255 (3) ◽  
pp. 929-935 ◽  
Author(s):  
J M Duerden ◽  
G F Gibbons
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Diurnal Variation ◽  
Low Density Lipoprotein ◽  
Specific Radioactivity ◽  
Lipid Synthesis ◽  
Density Lipoprotein ◽  
Dark Phase ◽  
Light Phase

Hepatic lipid synthesis was measured in rats in vivo with 3H2O, and the appearance of label in triacylglycerol and its constituent fatty acid and glycerol moieties was determined. In rats treated with Triton WR1339, the amount of newly synthesized fatty acid secreted as very-low-density lipoprotein (VLDL) triacylglycerol was greater during the dark phase of the diurnal cycle than during the light phase (11.3 versus 4.8 mumol of 3H2O/3 h per g of liver respectively). However, the total mass of VLDL triacylglycerol secreted remained constant, as did the amount of label in the secreted triacylglycerol glycerol. Newly synthesized fatty acids comprised only a small proportion of the total VLDL triacylglycerol fatty acids (TGFA) at both times (dark phase, 7.7%; light phase, 2.4%). Starvation for 24 h resulted in a small increase in the secretion of VLDL triacylglycerol. However, the contribution from newly synthesized fatty acids was decreased. Similar effects were observed in streptozotocin-diabetic animals. During the light and dark phases of the cycle, similar quantities of newly synthesized TGFA entered the hepatic cytosol, and these amounts were much smaller than those secreted as VLDL triacylglycerol. The mass of cytosolic triacylglycerol showed a diurnal variation, with a greater concentration during the light phase than in the dark. In diabetes, the mass of triacylglycerol was increased in the cytosol, as was the incorporation of labelled acylglycerol glycerol. Diabetes also abolished the diurnal variation in the quantity of cytosolic triacylglycerol. In each group of animals the specific radioactivity of the microsomal triacylglycerol was similar to that of the respective newly secreted plasma VLDL. The specific radioactivity of the cytosolic triacylglycerol was only 15.8% (dark phase) or 16.8% (light phase) that of the microsomal triacylglycerol. This increased to 35.5% in the starved animals and 40.2% in the diabetic animals.

scholarly journals Regulation of lipogenesis. Stimulation of fatty acid synthesis in vivo and in vitro in the liver of the newly hatched chick

1970 ◽  
Vol 118 (2) ◽  
pp. 259-263 ◽  
Author(s):  
Alan G. Goodridge
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Acid Synthesis ◽  
Latent Form ◽  
Triose Phosphate ◽  
Liver Slices ◽  
Stimulation Of

1. A single glucose meal stimulated the incorporation of acetate into fatty acids in liver slices. If the glucose was added in vitro, it had no effect. Fructose and glycerol in vitro markedly stimulated fatty acid synthesis from acetate. Fructose and glycerol probably by-passed a rate-controlling reaction between glucose and triose phosphate. This reaction may have been stimulated by glucose administered in vivo. 2. The stimulation of fatty acid synthesis caused by fructose did not require the synthesis of enzyme, thus indicating that fatty acid-synthesizing enzymes were present in a latent form in the livers from unfed chicks.

scholarly journals Metabolism of phospholipids and the characterization of fatty acids in bovine corpus luteum

1968 ◽  
Vol 108 (2) ◽  
pp. 317-323 ◽  
Author(s):  
T. W. Scott ◽  
W. Hansel ◽  
L. E. Donaldson
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Polyunsaturated Fatty Acids ◽  
Neutral Lipids ◽  
Total Phospholipid ◽  
Lipid Fraction ◽  
Specific Radioactivity ◽  
Lactate Production ◽  
Corpora Lutea ◽  
Luteal Tissue

1. Phosphatidylcholine was the predominant phospholipid in bovine corpora lutea; it accounted for about 50% of the total phospholipid phosphorus. Phosphatidylethanolamine (13%) and ethanolamine plasmalogen (8–9%) were the next two major components. 2. After incubation of the tissue with [32P]orthophosphate the total radioactivity and specific radioactivity of phosphatidylinositol were higher than those of any other lipid. 3. Luteinizing hormone failed to increase significantly the incorporation of [32P]orthophosphate into total phospholipids from luteal tissue slices, but did stimulate progesterone synthesis and lactate production. 4. The proportion of oleate (18:1) in the neutral lipids and phospholipids was higher than that of any other fatty acid. 5. The proportion of unsaturated fatty acid in the tissue lipids exceeded 60%, and almost half of this was polyunsaturated. Arachidonate (20:4), docosatetraenoate (22:4) and docosapentaenoate (22:5) were the principal polyunsaturated fatty acids. 6. After incubation of luteal tissue with [1−14C]acetate, the greatest proportion of radioactivity in the fatty acids isolated from the total lipid fraction was in palmitate (16:0) and docosatetraenoate (22:4). Polyunsaturated fatty acids accounted for almost 50% of the 14C radioactivity incorporated and this pattern was observed in phospholipids, triglycerides and free fatty acids.

Effects of Acipimox, a Nicotinic Acid Derivative, on Lipolysis in Human Adipose Tissue and on Cholesterol Synthesis in Human Jejunal Mucosa

1985 ◽  
Vol 68 (1) ◽  
pp. 83-88 ◽  
Author(s):  
C. Stirling ◽  
M. McAleer ◽  
J. P. D. Reckless ◽  
R. R. Campbell ◽  
D. Mundy ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Fatty Acid ◽  
Cholesterol Synthesis ◽  
Density Lipoprotein ◽  
Human Adipose Tissue ◽  
Jejunal Mucosa ◽  
Acetate Incorporation ◽  
Precursor Pool

1. The mode of action of acipimox (5-methyl-pyrazine carboxylic acid 4-oxide), an hypotriglyceridaemic agent, was examined in human adipose tissue and intestinal mucosa. 2. The rates of release of fatty acids and glycerol from human adipose tissue were measured in vitro. The release of fatty acids and glycerol from adipose tissue maximally stimulated by isoprenaline (10−5 mol/l) fell by 40 and 25% respectively (P<0.025 and P<0.025) in the presence of acipimox (10−5 mol/l). In submaximally stimulated adipose tissue (isoprenaline 10−7 mol/l) acipimox (10−4 mol/l) fully inhibited release of fatty acids (P<0.05) and glycerol (P<0.025) to basal rates. In unstimulated adipose tissue acipimox (10−3 mol/l) reduced the rate of glycerol release (P<0.05), but not the rate of fatty acid release. 3. Cholesterol synthesis in jejunal mucosa was measured in vitro by the incorporation of [2-14C]-acetate into sterols. Addition of cholesterol to the incubation reduced [2-14C]acetate incorporation into sterols from 8.7 ± 2.1 (mean ± standard error) to 3.7 ± 1.0 pmol h−1 mg−1 of tissue (P<0.01). Acipimox at 10−4-10−2 mmol/l had no consistent effect on cholesterol synthesis. 4. Acipimox appears to exert its main hypolipidaemic effect by reducing lipolysis and free fatty acid flux to the liver, thereby reducing the precursor pool size of very low density lipoprotein (VLDL)-triglyceride and VLDL synthesis.

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