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1.
The influence of lipolytic mechanisms on the transfer of phospholipids and unesterified cholesterol from artificial emulsions,
serving as chylomicron models to other plasma lipoproteins, mainly high density lipoproteins (HDL) were testedin vivo. The emulsions labeled with radioactive lipids were injected into the bloodstream of rats (controls) and the results were
compared with those obtained from rats that had previously been treated with Triton WR 1339 or heparin. Plasma clearance and
the distribution of cholesteryl esters, phospholipids and unesterified cholesterol in the different plasma lipoprotein fractions
were then determined. Whereas virtually no cholesteryl esters were found in d>1.006 g/mL density fraction of the three experimental
groups, 2.8±1.3% of the injected phospholipids were in the 1.063–1.210 g/L density fraction of the Triton treated rats, and
12.6±5.4% of the heparin treated rats, as compared to 10.1±1.7% in controls. This indicates that lipolysis directly influences
phospholipid transfer to HDL. In contrast, free-cholesterol transfer to HDL, besides being less pronounced than phospholipid
transfer, was enhanced by Triton and diminished by heparin, indicating that lipolytic mechanisms were not important determinants
in this process.
This work is part of a Privatdozent Thesis by the corresponding author. 相似文献
2.
Male rats were administered 1.5 ml safflower oil by gastric intubation 0, 4, and 8 hr after a 16 hr fast. Plasma, liver, and adipose tissue were collected 16 hr after the last fatty meal. Rats fasted for 16 hr served as controls. Following fat feeding, the fatty acid composition of the very low density lipoprotein, triglyceride, and hepatic triglyceride were similar, as were the percentages of 18:2 in the very low density lipoprotein and hepatic cholesteryl esters. The phospholipids of liver and plasma lipoproteins were similar in the control groups, except that more 16:0 was present in the plasma lipoproteins. After fat feeding, the plasma lipoproein phospholipids were enriched with 18:2 more than were the hepatic phospholipids. Furthermore, the percentage of 18:2 in phospholipid was much less than in triglyceride or cholesteryl esters. Clearly, esterified lipids of liver and plasma lipoproteins (very low density lipoprotein, low density lipoprotein, and high density lipoprotein), and to a lesser extent, adipose tissue, were enriched with 18:2 derived from dietary triglyceride fatty acid even 16 hr after the terminal meal. A major proportion of the very low density lipoprotein isolated by ultracentrifugation in zonal rotors from plasma of fat fed animals had a faster rate-zonal mobility than did the very low density lipoprotein isolated from plasma of control animals. The very low density lipoprotein isolated from plasma of fat fed rats contained fewer moles of phospholipids, cholesterol, and cholesteryl esters, relative to triglyceride than did the very low density lipoprotein from plasma of animals not receiving safflower oil. The molar ratio triglyceride:phospholipid:cholesterol:cholesterol esters in the very low denity lipoprotein was 100:42.0:22.1:44.5 in the control group and 100:35.4:17.8:19.5 in the fat fed animals. It is postulated that an important biochemical mechanism by which dietary triglyceride fatty acids consumed by the animal over a long period of time alter plasma concentrations of triglyceride, phospholipids, and cholesterol esters is the directive influence of plasma free fatty acid, derived from dietary triglyceride, on the secretion of very low density lipoprotein lipids by the liver. 相似文献
3.
This report describes a series of experiments that attempt to characterize the lipidemia accompanying retinoic acid administration.
After feeding young adult male Sprague-Dawley rats, 1.2 Retinol Equivalents (R.E.) retinyl acetate plus supplemental retinoic
acid (100 μg/g dry diet) for three days and fasting for 6–8 hr, triglyceride, cholesterol, and phospholipid content of various
serum lipoprotein fractions were determined. When compared to unsupplemented controls, both the serum very low density lipoprotein
(VLDL) and the high density lipoprotein (HDL) fractions of the retinoic acid-fed rats were found to harbor an elevated triglyceride
content. While VLDL cholesterol and phospholipid content were also elevated, total serum cholesterol and phospholipids were
not statistically altered. The detergent Triton WR-1339 was used to depress serum triglyceride clearance in order to assess
the effects of retinoic acid feeding on serum triglyceride levels. Triglyceride accumulation started earlier after Triton
treatment and was greater when rats were fed 100 μg/g retinoic acid for three days prior to testing. Red and white gastrocnemius
muscle, cardiac ventricular muscle, and perirenal adipose tissue were removed from rats following retinoic acid feeding. Analysis
of these tissues for lipoprotein lipase (EC 3.1.1.3) activity showed a decrease in adipose tissue, a large depression in both
areas of gastrocnemius muscle and no change in cardiac muscle as a result of retinoic acid feeding.
Portions of this work have appeared earlier in an abstract, Gerber, L.E., and Erdman J.W., Jr. (1980) Fed. Proc. 39, 437. 相似文献
4.
Estradiol implants in chicks resulted in marked elevation of all major plasma lipids with greatest increase in triglyceride
(TG) followed by phospholipid (PL) and cholesterol (C). During the two-wk period, plasma TG level in estrogen (E)-treated
chicks increased to about 45 times that of controls (139.6 vs 6,368.3 mg/dl). The level of cholesterol also increased steadily
during the same period, attaining nearly a six-fold increase in comparison with the control (150.7 vs 871.8 mg/dl), and the
level of PL was markedly elevated from 209 to 2,861 mg/dl. Besides the induction of hyperlipidemia, E treatment also resulted
in a notable alteration in the fatty acid composition of plasma lipids; there was an increase in oleic acid concomitant with
a decrease in polyunsaturated fatty acids, particularly, linoleic acid. One day after implantation, the percentage of oleic
acid in TG fraction increased from 39.2 to 43.7%, reaching 55.4% of the total fatty acids at day 14. In contrast, the levels
of linoleic and arachidonic acid decreased significantly from 16.1 to 8.3% and 4.3 to 0.6%, respectively, during the same
period. In cholesteryl ester (CE) and PL, the oleic acid level also increased from 25.2 to 47.3% in the former and from 11.9
to 29.6% in the latter, reflecting enhanced hepatic lipogenesis. Analysis of plasma lipoproteins in E-treated chicks revealed
dramatic alterations in the concentrations of lipids and protein in individual lipoprotein fractions, especially very low
density lipoprotein (VLDL) fraction. The respective levels of TG, C and PL in the VLDL fractions were 10.0, 0.6 and 1.0 mg/dl
in the control, and 3,904.4, 530.3 and 1,365.2 mg/dl in chicks implanted with estrogen for seven days. The concentrations
of TG, C and PL also were markedly increased in the low density lipoprotein (LDL) fraction in these birds. However, the cholesterol
content of the high density lipoprotein (HDL) fraction was decreased dramatically in E-treated chicks (47.1) relative to the
control (121.5 mg/dl). The protein level in the VLDL fraction from E-treated chicks was profoundly elevated to a level 300-fold
greater than controls. TG secretion rates were measured in vivo following the administration of Triton WR-1339. In control
chicks, plasma TG secretion rate was 2.29 mg/min; whereas, chicks treated with E for one and three days showed significantly
higher TG secretion rates of 3.18 and 5.27 mg/min, respectively. TG removal rates were measured in vivo after administration
of a 10% fat emulsion. Although plasma TG concentrations were different between control and E-treated birds, no significant
differences were found in TG removal rates in those birds, indicating no impairment of TG clearance in E-treated chicks. 相似文献
5.
Administering 17β-estradiol (E2) to juvenile trout results in plasma hyperlipidemia and hyperlipoproteinemia associated with significant increases in the
concentrations of triglycerides (TG), free cholesterol, phospholipids, free fatty acids and proteins, both postprandial and
during starvation. TG undergo the greatest increase (9 times control level 96 h after feeding). The concentration differences
between E2-treated and control trout increase during starvation, primarily by progressive decreases in the concentrations of various
lipids in controls. E2-induced hypertriglyceridemia is mainly caused by an increase in the concentration of very low density lipoproteins (VLDL)
during both the postprandial period (6 times control level at 24 h) and during starvation (15 times control level at 96 h);
hyperlipoproteinemia lasts up to at least 7 d after the last feeding. E2 treatment does not change the concentration of high density lipoproteins, but does increase plasma concentrations of a very
high density lipoprotein, vitellogenin (VTG). In E2-treated VLDL, cholesteryl esters are depleted while proteins are enriched. During the postprandial phase, the apolipoprotein
(apo) profile of VLDL (d< 1.015 g/mL) is comparable in E2-treated and control trout. Starvation of E2-treated trout is accompanied by an enrichment in apo B240, A-I and A-II. The secretion levels of TG and VLDL-TG, as determinedin vivo, by injecting Triton WR-1339 to starving animals, are significantly higher in E2-treated trout than in controls. In trout, as in chicks, E2 administration significantly increases the concentration and hepatic secretion of plasma VLDL independent of the nutritional
status and the appearance of VTG in the plasma. This suggests the existence of similar mechanisms for the regulation of lipoprotein
metabolism by estrogens in oviparous vertebrates. 相似文献
6.
Ana Maria P. Lottenberg Helena C. F. Oliveira Edna R. Nakandakare Eder C. R. Quintão 《Lipids》1992,27(5):326-330
The mechanism by which ω3 fatty acids lower plasma triacylglycerol levels was investigated. Rats were fed fish oil, olive
oil (10% fat by weight) or a nonpurified diet 4% fat by weight) for 15 days. Lipoprotein lipase was inhibited by intra-arterial
administration of Triton WR 1339 to estimate hepatic triacylglycerol output. Rats fed the olive oil diet showed a higher rate
of triacylglycerol formation than rats fed the ω3 fatty acid diet or the low-fat diet. All three groups showed identical rates
of removal from plasma of intraarterially administered artificial chylomicrons that had simultaneously been labeled with cholesteryl
[1-14C]oleate and [9,10(n)-3H]triolein. Liver radioactivity and total fat content were lowest in rats fed the fish oil diet, indicating that ω3 fatty
acids were preferentially metabolized in liver. Chylomicrons obtained from donor rats fed either fish oil containg [14C]cholesterol or olive oil containing [3H]cholesterol were removed at similar rates when infused together intraarterially into recipient animals. A slower formation
of plasma very low density lipoprotein triacylglycerols in rats fed fish oil is probably due to a faster rate of oxidation
of the fatty acid chains in the liver resulting in decreased plasma triacylglycerol concentrations. 相似文献
7.
The composition of circulating very low density lipoprotein (VLDL) was compared with the composition and secretion of nascent
VLDL from perfused livers of squirrel monkeys that were fed unsaturated or saturated fat diets to elicit different degrees
of plasma hypercholesterolemia. All squirrel monkeys studied had cholesteryl ester-rich plasma VLDL, although greater enrichment
occurred in hypercholesterolemic animals fed saturated fat. Livers from hypercholesterolemic animals were capable of secreting
VLDL particles enriched in cholesteryl ester, suggesting hepatic origin for a portion of this circulating lipid moiety. Total
VLDL lipid, but not protein output by perfused livers of hypercholesterolemic monkeys, was greater than that by livers from
hypocholesterolemic animals. These results indicate that saturated fat-induced hypercholesterolemia is associated with changes
in the composition of hepatic VLDL in the squirrel monkey. 相似文献
8.
The effect of protein depletion in the pregnant rat on the polyunsaturated fatty acid incorporation into very low density
lipoproteins (VLDL) has been investigated. The apoprotein pattern of these particles was determined. In in vivo experiments
the amounts of serum and liver triacylglycerol were determined. VLDL were isolated and their apo C concentration calculated.
In in vitro experiments the radioactivity of [3H] leucine incorporated into VLDL apoproteins was measured. The results show that protein depletion during pregnancy promotes
a drastic increase in serum and liver triacylglycerol. The VLDL isolated from these animals show an increase in the triacylglycerol/protein
ratio and a decrease in their content of apo C. Meanwhile, a significant reduction in the [3H]leucine incorporation into apo C peptides by the perfused liver of protein depleted rats was detected. On the other hand,
protein deprivation did not affect labeled linoleic and arachidonic acid incorporation into triacylglycerol of the newly secreted
VLDL. Taking these results together, let us deduce that a defective VLDL is secreted by the liver of the protein depleted
pregnant rats. The abnormal composition of these particles may influence its normal metabolism through their effects on lipoprotein
lipase and this fact could affect the normal supply of polyunsaturated fatty acids to the fetus. 相似文献
9.
In rats with hyperlipemia induced by Triton WR-1339, changes in tocopherol concentrations in plasma and RBC were compared
with those in the liver and its subcellular fractions, microsomes and mitochondria.
After daily injection with Triton, plssma total lipids at 3 days and 7 days, respectively, showed elevation 6.5 times and
15 times as high as those in the control rats, and triglycerides showed the most predominant elevation.
With the hyperlipemia, the concentrations of tocopherol in RBC and the subcellular fractions decreased, as plasma lipids and
plasma tocopherol increased, while no change occurred in tocopherol concentrations in liver homogenates. The changes in the
ratio of tocopherol to total lipids in plasma coincided with changes in tocopherol concentrations in the RBC and subcellular
fractions. 相似文献
10.
Maria Luz Fernandez A. Karin Conde Laura R. Ruiz Carlos Montano John Ebner Donald J. McNamara 《Lipids》1995,30(7):619-626
To test the effects of exchanging dietary complex and simple carbohydrate for fat calories on lipoprotein metabolism, guinea
pigs were fed two different fat/carbohydrate ratios: 2.5∶58% (w/w) or 25∶29% (w/w) with either sucrose or starch as the carbohydrate
source. Animals fed high-fat had higher plasma low-density lipoprotein (LDL) and hepatic cholesterol concentrations than animals
fed low-fat diets (P<0.01). The cholesteryl ester content per particle was higher, and the number of triacylglycerol (TAG) molecules was lower
in very low density lipoprotein (VLDL) and LDL from animals fed high-fat diets. Intake of high-fat/sucrose resulted in higher
plasma LDL concentrations than intake of high-fat/starch, and animals fed low-fat/starch had the highest plasma TAG concentrations
associated with VLDL particles containing more TAG molecules, as well as a TAG-enriched LDL. The activity of plasma lecithin
cholesteryl:acyl transferase (LCAT) was highest in animals fed high-fat/sucrose, and heart lipoprotein lipase (LPL) activity
was higher in animals fed high-fat diets. Hepatic apoprotein B/E (apo B/E) receptor number (Bmax) was increased 21% with low-fat diets (P<0.01). These results suggest that the hypercholesterolemia induced by high-fat and by sucrose intake are associated with
a higher plasma LCAT activity which results in a cholesteryl ester-enriched VLDL which, by the action of LPL, might be more
readily converted to LDL through the delipidation cascade leading to downregulation of hepatic apo B/E receptors. The hypertriglyceridemia
associated with low-fat intake may result from increased production of VLDL TAG, which would explain the increased TAG content
and the higher TAG/CE ratio of VLDL from animals fed the low-fat/starch diet. 相似文献
11.
The effect of a saturated fat diet on the apoprotein composition and radioiodination properties of plasma very low density
lipoprotein (VLDL) was studied in rats. After feeding the diet for 10 days, the proportion of125I attached to VLDL lipid decreased from 50% (control animals) to 8%, the remainder (92%) being bound to the apoportein components.
The decreased lipid labelling was associated with proportional changes in the fatty acid composition of serum and VLDL lipids,
the most notable change being a reduction in linoleic acid (30–8%) content which occurred in all the major lipid classes of
both serum and VLDL. Analysis of VLDL after radioiodination showed that most of the radioactivity incorporated into the lipid
moiety was associated with phospholipid. The proportion of125I bound to phospholipid decreased after feeding rats a saturated diet. The proportion of soluble (small molecular weight peptides
and arginine rich peptide) to insoluble (B apoprotein) did not alter during the saturated fatty acid dietary regime and no
differences in the distribution of soluble proteins were observed. It is concluded that feeding a saturated fat diet to rats
for 10 days significantly improved125I labelling of the apoprotein moiety while apparently not inducing changes in apoprotein composition. 相似文献
12.
The influence of hypercholesterolemia on the triglyceride secretion rate was studied in both squirrel and cebus monkeys fed
coconut oil, corn oil, or safflower oil. The triglyceride secretion rate (TGSR) was determined in vivo following the administration
of Triton WR1339, which blocks the clearance of very low density lipoprotein (VLDL). Thus, the increase observed in circulating
triglyceride after Triton administration presumably reflects hepatic triglyceride (VLDL) secretion in the fasted state. The
VLDL-TGSR was lowest in hypercholesterolemic monkeys and highest in those fed unsaturated fat diets and having a low serum
cholesterol. In all instances, TGSR was inversely correlated with the plasma cholesterol concentration. While a definitive
explanation for these observations must await further investigation, the possibility that circulating low density lipoprotein
(LDL) acts to feed back on VLDL secretion is discussed. The decreased TGSR associated with the diet-induced cholesterolemia
also implies clearance of VLDL is impaired under these conditions. 相似文献
13.
Yorkshire (lean) and Ossabaw (obese) swine ca. one year of age were used to characterize the quantity and composition of plasma
lipoproteins in animals with markedly different adiposity. While lean swine weighed more (175 vs 88 kg for obese), they had
less backfat than obese swine (2.64 vs 5.97 cm; P<0.05). Fasting plasma triacylglycerol (Tg) and cholesterol (CH) levels were
elevated in obese swine. Swine plasma lipoproteins were fractionated into very low density lipoprotein (VLDL; d<1.006), low
density lipoprotein1 (LDL1; d=1.019–1.063), low density lipoprotein2 (LDL2; d=1.063–1.09), and high density lipoprotein (HDL; d=1.09–1.21) by density ultracentrifugation. Obese VLDL-Tg, CH and protein
(Pr) were elevated more than 2-fold. VLDL from obese swine were 2-fold larger than VLDL from lean swine. No alterations in
LDL1 or LDL2 composition were observed. HDL-Tg, CH, Pr and phospholipid levels were significantly higher in obese swine. Plasma and VLDL-Tg
levels were highly correlated with backfat thickness (r=0.67 and r=0.73, respectively). These was a positive correlation between
adiposity and HDL-CH as well as VLDL-Tg and HDL-CH. These data indicate that (a) there are marked alterations in swine plasma
lipoprotein composition between lean and obese swine; (b) that swine plasma lipoprotein levels may be useful parameters in
estimating body composition; and (c) that HDL-CH is positively correlated with adiposity in swine.
Department of Dairy and Animal Science, College of Agriculture.
Nutrition Program, College of Human Development. 相似文献
14.
The fatty acid compositions of plasma cholesteryl esters (CE) and triacylglycerols (TG) from seven healthy individuals and
five patients with type V hyperlipoproteinemia were determined. Very low density (VLDL), low density (LDL) and high density
lipoproteins (HDL) were isolated. The lipids were extracted from the lipoproteins and the triacylglycerols and cholesteryl
esters separated for analysis. The fatty acid compositions of triacylglycerols from healthy and type V individuals were very
similar. The cholesteryl esters from type V patients had increased contents of palmitic and decreased amounts of linoleic
and arachidonic acids as compared to the normal individuals. The fatty acid composition of the cholesteryl esters from the
high density lipoproteins had the greatest deviation. The fatty acid compositions of the triacylglycerols from the two groups
were similar. However, the triacylglycerols in all lipoprotein fractions contained more palmitic and oleic and less linoleic
and arachidonic acids than the cholesteryl esters. 相似文献
15.
To address the role of cell membrane neutral sphingomyelinase (EC 3.1.4.12; SMase) in the regulation of cholesterol metabolism
in the liver parenchymal cell, we examined the effect of exogenous neutral SMase on the metabolism of cholesteryl esters and
the secretion of VLDL and biliary lipids in isolated rat hepatocytes. We show that treatment of hepatocytes with SMase (20
mU/mL) resulted in the intracellular buildup of cholesteryl esters, increased ACAT (EC 2.3.1.26) activity without affecting
the ACAT2 mRNA level, and increased cytosolic and microsomal cholesteryl ester hydrolase (EC 3.1.1.13) activity. This was
accompanied by increases in the secretion of biliary. bile acid, phospholipid, and cholesterol and in increased cholesterol
7α-hydroxylase (EC 1.14.13.17) activity and levels of mRNA, as well as decreased levels of apoB mRNA and a decreased secretion
of VLDL apoB (apoB-48, ∼45%; apoB-100, ∼32%) and lipids (∼55%). Moreover, the VLDL particles secreted had an abnormal size
and lipid composition; they were larger than controls, were relatively enriched in cholesteryl ester, and depleted in TG and
cholesterol. Cell-permeable ceramides did not replicate any of the reported effects. These findings demonstrate that the increased
cholesteryl ester turnover, oversecretion of biliary cholesterol and bile acids, and undersecretion of VLDL cholesterol and
particles are concerted responses of the primary hepatocytes to exogenous neutral SMase brought about by regulation at several
levels. We suggest that plasma membrane neutral SMase may have a specific, ceramide-independent effect in the regulation of
cholesterol out-put pathways in hepatocytes. 相似文献
16.
Two isoflavones, biochanin-A and formononetin isolated from gramCicer arietinum, have been shown to possess hypolipidemic properties for Triton WR-1339 induced hyperlipidemia in male albino rats, when
administered as a crude extract or as individual compounds. 相似文献
17.
l-Carnitine plays an important role in the mitochondrial uptake of long-chain fatty acids in mammals. It has recently been
shown that this compound has a marked hypo-cholesterolemic effect when used in conjunction with lipid-rich diets. The aim
of this study was to investigate the effects of l-carnitine on the fatty acid composition of plasma lipoproteins in rabbits fed with different diets. Four different groups
were investigated: group I (standard diet), group II (standard diet supplemented with l-carnitine at 80 mg/kg), group III (standard diet supplemented with 0.5% cholesterol), and group IV (standard diet supplemented
with 0.5% cholesterol plus l-carnitine at 80 mg/kg). The feeding period was 126 d. Total plasma cholesterol was indistinguishable in groups I and II,
but increased nearly 40-fold in group III. This increment was reduced by 50% in group IV. Correspondingly, total cholesterol
content in lipoprotein fractions [very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein
(HDL) separated by agarose gel chromatography was the same for groups I and II, while for animals fed a cholesterol-rich diet
(III) total cholesterol in VLDL+LDL increased nearly 100-fold when compared with groups I and II but, again, the increment
was reduced by 50% in group IV. In contrast, total cholesterol in HDL increased only fivefold for both groups III and IV when
compared with groups I and II, indicating no effects of l-carnitine on this parameter. The reduction of total cholesterol in VLDL+LDL particles in animals fed a cholesterol-rich diet
plus l-carnitine was associated with a marked decrease in the ratio of cholesteryl ester to free cholesterol and a dramatic increase
in their phospholipid content; opposite effects were observed for HDL. l-Carnitine induced a marked decrease in the saturated to unsaturated C16+C18 fatty acid ratio in cholesteryl esters associated with VLDL and LDL from animals fed with both normal and cholesterol-rich
diets. The opposite effect (a large increase in the saturated to unsaturated fatty acid ratio) was observed for both cholesteryl
esters and phospholipids associated with HDL in animals fed with both diets. The results suggested that the hypocholesterolemic
effects of l-carnitine could be associated with increased systemic breakdown of cholesteryl esters, a probable increase in reverse cholesterol
transport, and the stabilization of a phospholipid-based structure of VLDL+LDL particles. 相似文献
18.
Nozomu Takeuchi Mitsuharu Murase Yasuharu Nomura Haruto Takase Kiyohisa Uchida 《Lipids》1987,22(8):566-571
In order to investigate the effect of hepatic cholesterol flux on biliary bile acids, Triton WR 1339 and orotic acid were
administered to rats, and the biliary cholesterol, phospholipids and bile acids were analyzed together with serum lipoproteins
and hepatic lipids. Triton, which raised serum very low density lipoprotein and lipid levels and decreased serum high density
lipoprotein liver lipid levels, increase the biliary cholic acid group/chenodeoxycholic acid group ratio (CA/CDCA) in the
bile without affecting the total amount of bile acids and the other biliary lipids. Orotic acid, which decreased serum lipid
and lipoprotein concentrations and increased liver lipid levels, increased the biliary excretion of cholesterol and phospholipids,
but produced no significant change in the total amount of bile acids and in the CA/CDCA ratio in bile. 相似文献
19.
Nicotine, a major component of cigarette smoke, plays an important role in the development of cardiovascular disease and lung
cancer in smokers. The effect of nicotine on lipoprotein metabolism was studied using rats as the experimental animal. There
was a significant increase in the total cholesterol, phospholipids, and triglycerides as well as the amount of lipids associated
with very low density lipoprotein (VLDL) and low density lipoprotein (LDL) in sera of nicotine-treated rats. The incorporation
of 3H labeled leucine into the apo B was found to be increased both in the medium and associated cells in the hepatocytes isolated
from nicotine-treated rats indicating an increased synthesis and secretion of the apo B containing lipoproteins. This was
further confirmed by the higher incorporation of 14C acetate into total and individual lipids of LDL and VLDL secreted into the medium as well as that associated with different
lipids in the cell layer. The activity of lipoprotein lipase in extrahepatic tissues and plasma lecithin cholesterol acyltransferase
activity were significantly lower in nicotine-treated rats. These results indicate that nicotine exerts hyperlipidemic effects
particularly by increasing the synthesis and secretion of triglyceride-rich lipoproteins. Since nicotine is one of the major
hazardous components present in cigarette smoke and tobacco, one can extrapolate that the deleterious effect exerted by nicotine
on rats extends to cigarette smokers and those who use other forms of tobacco. 相似文献
20.
Wolfgang Sattler Helga Reicher Pilar Ramos Ute Panzenboeck Marianne Hayn Hermann Esterbauer Ernst Malle Gerhard M. Kostner 《Lipids》1996,31(12):1303-1310
A simple, accurate, and fast procedure for quantitative analysis of fatty acids (FA) in simple lipid subclasses from different
biological specimens is presented. Lipid extracts of isolated plasma lipoproteins (very low, low, and high density lipoproteins;
VLDL, LDL, and HDL, respectively) and permanent J774 mouse macrophages were fractionated into lipid subclasses by thin-layer
chromatography (TLC) on silica gel 60 plates. Bands comigrating with authentic lipid standards were scraped off under argon
and subjected to direct,in situ transesterification with BF3/MeOH in the presence of the TLC adsorbent. Fatty acid methyl esters were subsequently quantitated by capillary gas chromatography.
A comparison of the FA content present in total lipid extracts and in lipid subclasses separated by TLC revealed recoveries
ranging from 93 (J774 cell extracts) to 99.7% (LDL). The method described is applicable for the measurement of FA in individual
lipid subclasses and was successfully applied to quantitatively analyze the FA composition of the phospholipid, triacylglycerol,
and cholesteryl ester fraction derived from VLDL, LDL, and HDL. In J774 lipid extracts, the FA composition of the phospholipid-,
monoacylglycerol-, diacylglycerol-, free fatty acid-, triacylglycerol-, and cholesteryl ester fraction was quantitated. In
addition we have analyzed the time-dependent loss of the major HDL polyunsaturated fatty acids (18:2, 20:4) in the phospholipid
and cholesteryl ester fraction during copper-dependent peroxidation of HDL. We have not encountered analytical problems concerning
low FA recoveries from CE-rich lipid extracts as indicated by almost quantitative recoveries of FA in LDL, HDL, and J774 extracts. 相似文献