The regulation of cholesterol metabolism in rat adrenal glands, especially the effect of ACTH, cholesterol, and corticosteroids on acyl-coenzyme A (CoA) synthetase and cholesterol ester hydrolases was investigated. A significant increase in acyl-CoA synthetase activity and decrease in cholesterol ester hydrolase activities were observed in 24-h hypophysectomized rats. Acute injection ...

The influence of membrane cholesterol on the activities of acyl-CoA: cholesterol acyltransferase and 3-hydroxy-3-methylglutaryl-CoA reductase was examined in three microsomal subfractions (RNA-rich, RNA-poor, and smooth) that had been enriched with cholesterol by incubation with mixed lipoproteins from hypercholesterolemic rabbit serum. Acyl-CoA: cholesterol acyltransferase activity was significantly stimulated in the three ...

Incubation of monkey arterial smooth muscle cells with hyperlipidemic serum or low-density lipoproteins (LDL) produces intracellular cholesterol ester accumulation. Increased esterification of free cholesterol within the cell may account for this effect. To examine such a possibility, oxygenated sterols were used to block cholesterol esterification. The increased esterification of free ...

Fifteen healthy volunteers were put on a mackerel and herring diet, consisting of a prescribed daily isocaloric regimen in a cross-over design, for 2 weeks. Eicosapentaenoic acid (EPA - C20:5, n-3) was predominantly incorporated into cholesterol esters, whereas docosahexaenoic acid (C22:6, n-3) appeared more in serum triglycerides, indicating that the ...

The use of retinyl ester as a tracer for chylomicrons and chylomicron remnants depends on the observation that newly absorbed dietary retinol is transported as retinyl ester in plasma chylomicrons or chylomicron remnants and also on the assumption that organs other than intestine do not contribute retinyl ester to plasma. ...

Mouse peritoneal macrophages can be induced to accumulate cholesteryl esters by incubating them in the presence of acetylated low density lipoprotein. The cholesteryl esters are sequestered in neutral lipid droplets that remain in the cell even when the acetylated low density lipoprotein is removed from the culture media. Previous biochemical ...

The regulation of rabbit intestinal acyl CoA:cholesterol acyltransferase (ACAT) by 25-hydroxycholesterol was studied. 25-Hydroxycholesterol significantly increased jejunal microsomal ACAT activity. The stimulation of ACAT activity by 25-hydroxycholesterol was inversely related to microsomal cholesterol content. In enterocytes, 25-hydroxycholesterol stimulated cholesteryl ester synthesis 6-fold. The esterification of cholesterol, taken up by enterocytes ...

The study was undertaken to investigate the metabolic rat of post-lipolysis mesenteric lymph small chylomicrons produced in vitro. Small chylomicrons doubly labeled with [3H]cholesterol (more than 70% in cholesteryl esters) and [14C]palmitate-labeled triglycerides were collected from rat mesenteric lymph during periods of fasting. Lipolysis was performed in vitro with lipoprotein ...

Nonhuman primates consuming diets containing cholesterol develop coronary artery atherosclerosis that we have found to be highly correlated with an increase in the size and cholesteryl ester content of plasma low density lipoproteins (LDL). The present studies were designed to determine whether the enlarged plasma LDL are produced directly by ...

The effect of Anna Pavala Sindhooram (APS), an indigenous drug showing lipid lowering action was tested in experimental rat atherosclerosis induced by feeding an atherogenic diet. APS was found to decrease the levels of serum cholesterol and phospholipids while triglycerides remained unaffected in atherogenic diet fed rats. Lipid levels in ...

The preincubation at 37 degrees C of rat liver microsomal fraction, followed by re-isolation of the treated vesicles, results in a time-dependent increase in the activity of acyl-CoA: cholesterol acyltransferase. The presence of cholesterol-phospholipid (1:1, mol/mol) liposomes results in higher rate of increase in activity and under these conditions the ...

Peripheral lymph high density lipoproteins (HDL) of the cholesterol-fed dog differ in a number of characteristics from plasma HDL of the same animal. Their high content of free cholesterol, phospholipid, apoprotein E, and apoprotein A-IV, their greater heterogeneity in size, and the presence of many discoidal particles suggest that a ...

The effect of phospholipid fatty acyl composition on the activity of acylcoenzyme A:cholesterol acyltransferase was investigated in rat liver microsomes. Specific phosphatidylcholine replacements were produced by incubating the microsomes with liposomes and bovine liver phospholipid-exchange protein. Although the fatty acid composition of the microsomes was modified appreciably, there was no ...

In incubations of plasma containing lipoproteins at physiological concentrations it has been confirmed that high-density lipoproteins (HDL) are the major initial recipients of the esterified cholesterol formed in the reaction catalysed by lecithin:cholesterol acyltransferase. It has also been confirmed, however, that a small proportion of the esterified cholesterol of lecithin:cholesterol ...

The acylcoenzyme A:cholesterol acyltransferase (ACAT) activity in liver microsomes from rats fed a diet containing 14% menhaden oil (Mp) for 11 days was 117% higher than that in microsomes from rats fed a corresponding diet containing 14% cocoa butter (Ms). There were no differences in the cholesterol and phospholipid contents ...

Nine even-numbered saturated (C4 to C20) and two unsaturated (C18:1, C18:2) cholesterol alkyl ethers were studied by differential scanning calorimetry, polarizing microscopy, and X-ray powder diffraction. Seven of the nine saturated ethers examined melt into stable liquid crystal mesophases. Mesophase transition temperatures vary over a much narrower range than in ...

Cholesteryl iopanoate, the prototype for a new class of lipid-soluble, site-specific contrast agents, has undergone preliminary evaluation for organic-specific uptake. This report describes the tissue distribution profile of this radioiodinated sterol ester in the rabbit as a function of time following intravenous injection of tracer doses. Selective accumulation of this ...

Cholesterol and retinol are both esterified with long-chain fatty acid within the mucosal cells of the small intestine. The reactions are catalyzed by microsomal acyl-CoA:cholesterol and acyl-CoA:retinol acyltransferases (EC 2.3.1.26, and EC 2.3.1.-, respectively). To gain more insight into the physiological importance of these acyltransferases, they were studied in villous ...

Although serum lecithin:cholesterol acyltransferase (LCAT) activity is known to be modulated by nutritional factors, little is known about the effects of dietary carbohydrate on this enzyme. Therefore, LCAT activities were assessed in cynomolgus monkeys fed diets for 6 weeks on 4 diets containing 77% of calories as sucrose or starch ...

Masses of crystals, which were largely composed of cholesteryl esters, were found in a porcine aortic valvular bioprosthesis removed eight years after implantation in the mitral position in a patient with rheumatic mitral valvular stenosis. Histologic sections of grossly raised and nonraised yellow lesions in the three cusps of this ...

The use of five cholesterol ester hydrolases (CEH), numbered 1 to 5, for the enzymatic determination of total cholesterol of human and rat serum are compared. All CEH gave approximately the same value (no statistical difference) for human serum. However, when rat serum cholesterol was determined, CEH-2 yielded a value ...

The transfer of cholesteryl esters and apolipoprotein E has been studied between plasma HDL and chylomicrons isolated either from ascitic fluid or from the plasma of a patient with type V hyperlipoproteinemia. Whereas apolipoprotein E transfer was rapid and occurred at low temperature, cholesteryl ester transfer was suppressed at 4 ...

Bezafibrate and clofibrate reduce the quantity of esterified cholesterol, decrease the incorporation of 14C-labeled oleic acid into cholesterol ester and inhibit acyl coenzyme A cholesterol acyltransferase activity in rabbit peritoneal macrophages stimulated with acetylated low density lipoprotein. In all cases, the effect of bezafibrate was more marked than that of ...

In 32 women of normal body weight who volunteered to participate in the study, the effect of rapid weight reduction by a low-calorie liquid diet on serum lipids and lecithin:cholesterol acyltransferase (LCAT) enzyme activity was studied. Women were on this 400 kJ/day diet for 7 days and fasting blood samples ...

1. CoA-dependent cholesterol esterification, measured as esterification of 3H-cholesterol, was demonstrated in homogenates of liver and intestinal mucosa of the char (Salmo alpinus L.). 2. Plasma concentration of triacylglycerols, unesterified and total cholesterol were significantly reduced to 43, 58 and 72% of the control values, respectively, after 6 weeks fasting. ...

In guinea pigs fed a diet enriched with 1% cholesterol, the liver, adrenals, spleen, and small intestine accumulated cholesterol much more than the lungs and kidneys. The cholesterol content of the aorta, stomach and colon was not increased by the diet. Cholesteryl ester was the predominant form of cholesterol deposited ...

Apolipoprotein A-I, the major protein of human plasma high density lipoprotein, is the primary activator of plasma lecithin:cholesterol acyltransferase. In vitro, the association of apolipoprotein A-I with physiological phosphatidylcholines can be catalyzed by mixing the protein and lipid with sodium cholate, which is removed by chromatography. The apolipoprotein A-I/phospholipid complex ...

When rabbits are fed a diet supplemented with cholesterol, their plasma cholesterol levels increase markedly, and they develop atherosclerosis. Most of the plasma cholesterol exists as cholesteryl esters in very low density lipoproteins (VLDL) and intermediate-density lipoproteins (IDL). The triglyceride content of the lipoprotein cores decreases sharply during cholesterol feeding. ...

The purpose of the present study was to test if the microsomal acyl-CoA:cholesterol acyltransferase (ACAT) in rat small intestine is regulated under physiological conditions. Two previously described in vitro assays were used, both based on the esterification of endogenous cholesterol with exogenous acyl-CoA, performed or generated during the incubation. The ...

Incubation of rat hepatocytes with oleate for a period of 1 h gave rise to a decrease in the total (esterified plus unesterified) cholesterol associated with very-low-density lipoprotein (VLDL). This effect was no longer apparent after longer incubation periods. The rate of cholesterol biosynthesis decreased during the first hour of ...

Eight oophorectomized women were given 1.25 mg esterified estrogens (EE) daily for 21 days and 5 mg medroxyprogesteroneacetate (MPA) daily for 5 days in a sequence combination. The effects on sex steroids, gonadotrophins, lipids and lipoproteins as well as the relative fatty acid composition of lecithin and cholesterol ester induced ...

Studies have been performed on groups of mini-pigs 21-23 months of age, which after 18 months of hypercholesterolemia (approximately 10 mmol) had developed raised atherosclerotic lesions with high levels of cholesterol esters, especially in the abdominal aorta and the coronary arteries. If the hypercholesterolemia was continued for 18 months, no ...

In vitro incubations of human or pig plasma containing a tracer amount of [3H]cholesterol have been performed to determine which lipoprotein fractions are the immediate recipients of the esterified cholesterol formed in the reaction catalysed by lecithin: cholesterol acyltransferase. In pig plasma, which is deficient in activity of the protein ...

The study of high density lipoprotein (HDL) alterations induced by serum incubation was undertaken by a new approach. Subfractions of HDL were separated by gradient gel electrophoresis, without preliminary ultracentrifugation, and were characterized by their size range. After dissolution of the polyacrylamide gel, each subfraction was analyzed for its total- ...

Either purified soya phosphatidylcholine (lecithin) or triacylglycerol (corn oil) were fed to rats on a diet containing 0.5% cholesterol. The diets contained similar amounts of linoleic acid. The effects of the two preparations on (a) serum cholesterol concentrations, (b) fatty acid profiles, (c) HMG-CoA reductase activity, (d) cholesterol absorption, and ...

Bezafibrate markedly reduced the activity of fatty acyl CoA:cholesterol acyltransferase (ACAT) in the microsomal fraction of aortas from cholesterol-fed rabbits, while clofibrate was a less potent inhibitor. The activity of lysosomal cholesterol ester hydrolase (LCEH) was not significantly affected by either agent, indicating that inhibition of ACAT rather than stimulation ...

The rate of intestinal cholesterol esterification may be an important determinant of the rates of entry and exit of cholesterol from the body. Acyl coenzyme A-cholesterol acyltransferase, the intracellular cholesterol esterifying enzyme, may play a role in this process. To assess this, the response of rabbit intestinal acyl coenzyme A-cholesterol ...

The role of lipoproteins and serum in the formation and accumulation of cholesteryl esters in human monocyte-derived macrophages (HMD macrophages) was investigated; studies were also carried out with IC21 cells (a cell line derived from mouse peritoneal macrophages). Following preincubation of HMD macrophages with lipoprotein-depleted serum (LPDS), both native and ...

The regulation of intestinal acyl-CoA: cholesterol acyltransferase was investigated by dietary manipulation. Rabbits were fed the following diets: normal rabbit chow, 10% safflower oil, safflower oil plus 1% cholesterol, coconut oil plus 1% cholesterol, or cholestyramine. Acyl-CoA: cholesterol acyltransferase activity was increased in intestinal microsomes from animals fed safflower oil ...

The corpus luteum of the rat stores large quantities of cholesteryl ester which is synthesized by acyl coenzyme A:cholesterol acyltransferase (ACAT), a microsomal enzyme. In previous studies of ACAT, assays that were probably substrate limited were employed. To reevaluate the regulation of ACAT in the ovaries of PMSG-hCG-primed rats, we ...

The in vitro preparation of HDL radiolabelled at the cholesteryl ester moiety was determined by incubating different serum fractions with [3H]cholesteryl linoleate or cholesteryl [14C]oleate dissolved in dimethylsulfoxide (DMSO) and subsequent re-isolation of HDL from the incubation mixture by ultracentrifugation. Using the supernatant obtained by precipitation of apolipoprotein B-containing lipoproteins ...

The initial rate of lecithin: cholesterol acyl transferase and serum concentration of lipids were determined in euthyroid, hypothyroid and hyperthyroid subjects. In hyperthyroid subjects, the serum levels of total and free cholesterol were significantly lower than in normal subjects and the fractional lecithin: cholesterol acyl transfer rate was significantly higher ...

The transport of cholesterol from extrahepatic tissues into plasma (reverse cholesterol transport) and the possible requirement for lecithin:cholesterol acyltransferase was examined in the rat. One hour after removal of the liver plasma cholesterol ester concentrations were significantly increased by 20%, whereas free cholesterol concentrations were unchanged. The lecithin:cholesterol acyltransferase inhibitor, ...

We have used Raman spectroscopy to investigate the effects of the general anaesthetics halothane and chloroform on lipid bilayer order. Clinical concentrations of these anaesthetics had no significant effect on the hydrocarbon chain conformation in multilamellar vesicles of dimyristoylphosphatidylcholine/cholesterol. This result was obtained with a technique sufficiently precise to monitor ...

A method has been devised for the preparation of stable lipid microemulsions containing cholesterol, cholesteryl ester, phosphatidylcholine, and trioleoylglycerol in the relative molar ratios found in low density lipoproteins. Gel permeation chromatography showed these microemulsions to be essentially homogeneous with respect to chemical composition. Omission of triolein or substitution of ...

Arteriosclerotic lesions were formed in rat aorta by the administration of vitamin D2, a high-fat diet and a thyroid suppressing agent. This treatment increased the serum total cholesterol level to 12 times the control level. In the arteriosclerotic lesions that were induced the activities of lysosomal enzymes, such as acid ...

The contribution of de novo synthesis to the secretion of cholesterol and lecithin in bile was assessed in isolated rat livers, perfused with a lipid-free medium. Cholesterol and lecithin synthesis were measured by the incorporation of tritiated water and [14C]-choline, respectively. Taurocholate stimulated the secretion of biliary lipids to the ...

Cholesterol esters and free cholesterol were determined in the serum of guinea-pigs with experimental allergic encephalomyelitis (EAE). EAE was induced by immunization with myelin basic protein (MBP). The results showed a marked decrease in cholesterol esters (CHE) 4 days after immunization. Seven days after immunization the values of esters increased ...

Changes in the rate of the plasma cholesterol ester production mediated by lecithin: cholesterol acyltransferase (LCAT, E.C. 2.3.1.43) were examined in 15 patients suffering from types II and IV HLP who had been treated for 14 weeks with etiroxate. Whereas the plasma cholesterol concentration decreased significantly only in the initial ...

Serum was incubated in vitro with and without inhibition of lecithin:cholesterol acyltransferase (LCAT, EC 2.3.1.43). High density lipoprotein2 (HDL2) and high density lipoprotein3 (HDL3) were separated by zonal ultracentrifugation and analysed for lipid and apoprotein contents. The incubation of fresh sera resulted in a time-dependent decrease in HDL3 and an ...