Serum and liver lipid composition and lecithin: cholesterol acyltransferase in horses, Equus caballus.

1. The lipid composition of serum and liver and some properties of serum lecithin: cholesterol acyltransferase of the horse were investigated. 2. Phospholipids and cholesterol were the major components of serum lipids and the concentration of triglyceride was considerably low. The concentration of liver lipids was comparable with that of other mammals. 3. Fatty acid composition of serum cholesterol ester resembled that of the 2-position of lecithin, except palmitic acid. 4. The activity of serum cholesterol esterifying enzyme was found to be 0.03-0.09 mumol/hr per ml. There was an equimolar decrease in free cholesterol and lecithin during incubation, and changes in unsaturated fatty acids in these two components were in good agreement. 5. Cholesterol esterification was reversibly inhibited by 5,5'-dithiobis-(2-nitrobenzoic acid). The acyl-transferase had a specificity for linoleic acid.     

Composition of plasma fatty acids and non-cholesterol sterols in anorexia nervosa

Anorexia nervosa is a model of simple starvation accompanied by secondary hyperlipoproteinemia. The pattern of plasma fatty acids influences the levels of plasma lipids and lipoproteins. The concentration of plasma lathosterol is a surrogate marker of cholesterol synthesis de novo, concentrations of campesterol and beta-sitosterol reflect resorption of exogenous cholesterol. The aim of the study was to evaluate fatty acids in plasma lipid classes and their relationship to plasma lipids, lipoproteins, cholesterol precursors and plant sterols. We examined 16 women with anorexia nervosa and 25 healthy ones. Patients with anorexia nervosa revealed increased concentrations of total cholesterol, triglycerides, HDL-cholesterol, campesterol and beta-sitosterol. Moreover, a decreased content of n-6 polyunsaturated fatty acids was found in all lipid classes. These changes were compensated by an increased content of monounsaturated fatty acids in cholesteryl esters, saturated fatty acids in triglycerides and both monounsaturated and saturated fatty acids in phosphatidylcholine. The most consistent finding in the fatty acid pattern concerned a decreased content of linoleic acid and a raised content of palmitoleic acid in all lipid classes. The changes of plasma lipids and lipoproteins in anorexia nervosa are the result of complex mechanisms including decreased catabolism of triglyceride-rich lipoproteins, normal rate of cholesterol synthesis and increased resorption of exogenous cholesterol.     

Studies on the origin of milk fat. A further study of bovine serum lipoproteins and an estimation of their contribution to milk fat

1. Tritium-labelled palmitic acid combined in olive-oil triglycerides was introduced into the rumen of a lactating cow and the specific radioactivity of the lipids of milk and of the lipoproteins of both jugular and mammary venous serum was measured. 2. As previously found in a similar experiment with [(3)H]stearic acid, the specific radioactivity of the triglyceride fraction of the dextran sulphate-precipitable lipoproteins reached a maximum earlier and greater than that of the milk fat. 3. This fraction was the only lipid separated that had a significant arteriovenous difference in concentration, and is therefore identified as the main circulating lipid precursor of milk fat. 4. Although the non-esterified fatty acids showed no arteriovenous difference in concentration, they showed a negative difference in specific radioactivity that could have occurred only at the expense of the triglycerides of the precipitable lipoproteins. 5. The mean specific radioactivity of the triglycerides immediately after removal from the blood is calculated and shown to be very close in value to that of the corresponding fraction in mammary venous serum. 6. By comparison of the mean specific radioactivities of milk fat and of this precursor, its contribution is calculated as 36%. 7. This value is discussed with reference to the concentration of C(16) and C(18) fatty acids in milk fat and it is concluded that substantial amounts of these acids must have been derived from a source other than preformed circulating lipids.     

Effect of dietary ghee--the anhydrous milk fat, on blood and liver lipids in rats

Dairy products are important sources of dietary fat in India. Anhydrous milk fat, viz., ghee, is consumed as such in the diet and also is used for frying the dishes. Ghee contains high levels of saturated fatty acids and cholesterol, which are considered risk factors for cardiovascular diseases. In the present study, ghee, at levels ranging from 0.25 to 10%, was included in a nutritionally balanced AIN-76 diet fed to Wistar rats for a period of 8 weeks. The serum lipid profiles of these animals showed a dose dependent decrease in total cholesterol, low density lipoproteins and very low density lipoproteins cholesterol, and triglyceride levels when ghee was present at levels greater than 2.5% in the diet. Liver cholesterol and triglycerides also were decreased in these animals. When ghee was included as a sole source of fat at a 10% level, polyunsaturated fatty acids in the serum and liver lipids were reduced significantly. Similar results were observed when ghee was subjected to a higher temperature (120 degrees C) to generate cholesterol oxidation products and fed to the animals. Although cholesterol oxidation products were not accumulated in serum, significant amounts were accumulated in liver only when ghee was fed as a sole source of fat at a 10% level. This study revealed that the consumption of ghee up to a 10% level in the diet altered blood lipid profiles in such a manner as not to elevate the risk factors for cardiovascular diseases.     

Hepatic lipid droplets. Isolation, morphology and composition

The floating lipid layer isolated centrifugation of rat liver was examined for composition and ultrastructure. It was chiefly composed of triglycerides and cholesterol esters plus much smaller amounts of free cholesterol, diglycerides, phospholipid and protein. No free fatty acids were detected. The triglyceride and cholesterol ester fractions consisted mostly of esters of linoleic acid, oleic acid and palmitic acid. Electron micrographs of the floating lipid layer revealed numerous spherical osmiophilic droplets having a mean diameter of 0.5-2mum with a very-thin dense outer coat. Similar structures were observed as organelles in electron micrographs of the intact liver cell. The amount of triglyceride in the layer decreased in rats starved for 72h, but pellet triglyceride (homogenate minus the floating lipid layer) was unchanged. These results suggest that the floating lipid layer is the representative in vitro of lipid-rich organelles which probably function as a depot form of hepatic-cell neutral lipid.     

Studies on lipogenesis in vivo. Lipogenesis during extended periods of re-feeding after starvation

1. Lipogenesis was studied in mice re-fed for up to 21 days after starvation. At appropriate times [U-(14)]glucose was given by stomach tube and incorporation of (14)C into various lipid fractions measured. 2. In mice starved for 48hr. and then re-fed for 4 days with a diet containing 1% of corn oil, incorporation of (14)C from [U-(14)C]glucose into liver fatty acids and cholesterol was respectively threefold and eightfold higher than in controls fed ad libitum. The percentages by weight of fatty acids and cholesterol in the liver also increased and reached peaks after 7 days. Both the radioactivity and weights of the fractions returned to control values after 10-14 days' re-feeding. These changes could be diminished by re-feeding the mice with a diet containing 20% of corn oil. Incorporation of (14)C from [U-(14)C]glucose into extrahepatic fatty acids (excluding those of the epididymal fat pads) was not elevated during re-feeding with a diet containing either 1% or 20% of corn oil. However, incorporation of (14)C from [U-(14)C]glucose into the fatty acids of the epididymal fat pads was increased in mice re-fed with either diet, as compared with non-starved controls. 3. Lipogenesis was also studied in mice alternately fed and starved. Mice given a diet containing 1% of corn oil for 6hr./day for 4 weeks lost weight initially and never attained the weight or carcass fat content of controls fed ad libitum. Incorporation of (14)C from dietary [U-(14)C]-glucose into the fatty acids of the epididymal fat pads was elevated threefold in the mice allowed limited access to food, although the incorporation into the remainder of the extrahepatic fatty acids was not different from that found for controls. Mice given a diet containing 20% of corn oil for 6hr./day adapted to the limited feeding regimen quicker and in 4 weeks did attain the weight and carcass fat content of controls. Incorporation of (14)C from [U-(14)C]glucose into the fatty acids of the epididymal fat pads and the remainder of the extrahepatic fatty acids was respectively fivefold and threefold higher than in controls fed ad libitum. 4. The elevation in liver lipogenesis during re-feeding was greatest on a diet containing 1% of corn oil, whereas in extrahepatic tissues the increase in lipogenesis was greater when the mice were re-fed or were allowed limited access to a diet containing 20% of corn oil. These results suggest that the causes of the increased rate of incorporation of (14)C from [U-(14)C]glucose into fatty acids during re-feeding may be different in liver from that in extrahepatic tissues.     

Identification of albumin-bound fatty acids as the major factor in serum-induced lipid accumulation by cultured cells

Factors responsible for the high lipogenic activity of rabbit serum were investigated using an assay procedure based on the gravimetric determination of the 24 hr increase in cell lipid. Cellular synthesis of fatty acids was inhibited by the presence of serum in the assay medium. Approximately 90% of the increase in cell lipid produced by serum fractions was due to triglyceride accumulation. Fractionation of rabbit serum by precipitation with ammonium sulfate or by ultracentrifugation in high density medium, both indicated that three-quarters of its lipogenic activity was associated with albumin. The lipoproteins prepared by ultracentrifugation also exhibited about one-half the activity of whole serum. The lipogenic activity of albumin was confirmed by the high potency of the albumin isolated in a nearly pure form from proteins of d>1.21 by precipitation with trichloroacetic acid and extraction with ethanol. As judged from chemical and isotopic analysis, neither the lipid content nor the lipid composition of the albumin was appreciably altered during its isolation. Of the albumin-bound lipids, only the free fatty acids, as determined by DEAE column chromatography, were present in an amount sufficient to account for the observed increase in cell triglycerides. In control experiments with horse serum of low lipogenic activity, the proteins of d>1.21 also possessed low activity in conjunction with a low content of free fatty acid. However, the albumin isolated from the latter preparation exhibited the high lipogenic activity of rabbit serum albumin. Chemical and isotopic analysis of the recovered horse serum albumin revealed that its free fatty acid content was the same as that of rabbit serum albumin. These results indicated that the isolation of horse serum albumin was attended by a substantial increase in its free fatty acid content. When the rabbit serum and horse serum content of media were adjusted to provide equivalent concentrations of albumin-bound fatty acids, the rabbit liver cells grown on the former media accumulated more lipid than cells grown on the latter media. This difference was shown to be due to the higher concentration of albumin per micro mole of fatty acid in horse serum as compared with rabbit serum. Consequently, the albumin to fatty acid ratio also controls the lipogenic activity of a serum. A linear relationship is presented which relates the cell lipid content to the molar ratio of albumin to free fatty acids and to the absolute concentration of free fatty acids in the medium.     

Succinic acid monoethyl ester, a novel insulinotropic agent: Effect on lipid composition and lipid peroxidation in streptozotocin–nicotin-amide induced type 2 diabetic rats

Succinic acid monoethyl ester (EMS) is recently proposed as an insulinotropic agent for the treatment of non-insulin dependent diabetes mellitus. Oxidative stress has been suggested to be a contributory factor in the development and complications of diabetes. In the present study the effect of EMS and Metformin on plasma glucose, insulin, serum and tissue lipid profile, lipoproteins and lipid peroxidation in streptozotocin–nicotinamide induced type 2 diabetic model was investigated. The carboxylic nutrient EMS was administered intraperitonially (8 μmol/g body weight) to streptozotocin diabetic rats for 30 days. The levels of thiobarbituric acid reactive substances (TBARS) and hydroperoxides in liver and kidney and serum and tissue lipids [cholesterol, triglycerides, phospholipids and free fatty acids] and very low density lipoprotein-cholesterol (VLDL-C) and low density lipoprotein-cholesterol (LDL-C), were significantly increased in diabetic rats, whereas the levels of high-density lipoprotein-cholesterol (HDL-C) and antiatherogenic index (AAI) (ratio of HDL to total cholesterol) were significantly decreased. The effect of EMS was compared with metformin, a reference drug. Treatment with EMS and metformin resulted in a significant reduction of plasma glucose with increase plasma insulin in diabetic rats. EMS also resulted in a significant decrease in serum and tissue lipids and lipid peroxidation products. These biochemical observations were supplemented by histopathological examination of liver and kidney section. Our results suggest the possible antihyperlipidemic and antiperoxidative effect of EMS apart from its antidiabetic effect.     

Age-related changes of lipid fractions and total fatty acids in the serum of female and male rats aged from 37 to 1200 days

1. Total lipids and the lipid fractions cholesterol ester, triacylglycerols, free cholesterol, free fatty acids and phospholipids as well as the fatty acid patterns of total lipids were measured in the serum of female and male rats (Wistar SPF, strain Hannover) aged 37-1213 days. 2. All parameters were monitored every 49th day. Five female and five male animals were used in each experiment. 3. All lipid fractions showed a significant positive linear regression vs age in both sexes. There were multiple significant differences in lipid fractions between the sexes. 4. Among the fatty acids only docosahexaenoic acid shows a significant correlation with age in both sexes.     

Serum fatty acids analysis by high performance liquid chromatography, after enzymatic hydrolysis and isolation by Sep-Pak C18 minicolumn

A simple method of high performance liquid chromatography for the determination of fatty acid composition of free fatty acid, triglyceride, cholesterol ester and phospholipid in 0.4 ml of human serum is described. The procedure includes the enzymatic hydrolysis of serum lipoproteins, the isolation of fatty acids using Sep-Pak C18 minicolumn, the p-bromo-phenacylester formation and the high performance liquid chromatography. Thirteen fatty acids including the internal standard separated into 10 peaks within a 30-min run. The recovery rates of Sep-Pak treatment were satisfactory. The coefficients of variation were 2-27%. The present method showed a limit of detection of 0.02-4 nEq fatty acid.     

Age-related changes of lipid fractions and total fatty acids in liver lipids and heart lipids of female and male rats aged 37-1200 days (liver) and 331-1200 days (heart)

1. Total lipids and the lipid fractions cholesterol ester, triacylglycerol, free cholesterol, free fatty acids and phospholipids, as well as the fatty acid patterns of total lipids, were measured in liver homogenates of female and male rats (Wistar SPF, strain Hannover) aged 37-1213 days. 2. The same parameters were measured in the apex of the heart in female and male rats aged 331-1213 days. 3. All parameters were monitored every 49th day. Five female and five male animals were used in each experiment. 4. The lipid fractions in liver showed a positive linear regression vs age, whereas all lipids in rat heart showed a negative regression vs age in both sexes. 5. The significance of regression vs age of fatty acids was much less than that in the lipid fractions of liver and heart of these animals.     

Induction of fatty liver by fasting in suncus

We found that a fatty liver was easily induced in a novel experimental animal, Suncus murinus (suncus), by withholding food. Hepatic triglyceride content increased linearly for up to 24 h after fasting in these animals. Serum levels of neutral lipids are very low in the fed state compared with those in rats, and decreased significantly after 24 h fasting. On the other hand, serum free fatty acids, which are at the same level in fed animals as in rats, increased threefold in the fasting suncus. In order to learn whether the fatty liver induced by fasting is an unusual physiological state or a pathological on-going state in suncus, they were refed after 24 h fasting. Refeeding resulted in a decrease in hepatic triglyceride content to the level of fed animals. Serum lipid levels, which decreased with fasting, returned to those of fed animals. This evidence indicates that hepatic lipid secretion is impaired even in a physiological state to some extent and that starvation causes increasing influx of free fatty acid to the liver, which might be followed by esterification and result in triglyceride accumulation in the liver. In conclusion, hepatic lipid and lipoprotein metabolism is unique to the suncus, which is a useful animal model for the study of intra-hepatic lipid transport.     

Studies on the lipid composition in serum and lymphocytes in chronic leukemia]

In 33 patients with chronic lymphatic leukaemia (CLL) the lipids were examined quantitatively and qualitatively in the serum and in the lymphocytes. Besides the 5 main categories of lipids, lysolecithin, sphingomyelin, lecithin and cephalin as well as cholesterol ester subfractions were determined according to their degree of saturation of their fatty acids. Patients suffering from CLL were found to have a moderately raise of serum triglycerides and an increase of cholesterol esters with simple unsaturated fatty acids. Simultaneously the fraction of ester with poly-unsaturated fatty acids is lowered. Leukaemic lymphocytes reveal in general a lowered total lipid content. It mainly consists of phosphatides and free cholesterol. Moreover, the leukaemic lymphocytes contrary to normal ones reveal a lowered content of cholesterol esters, diglycerides and triglycerides.     

Validation of a procedure for exogenous isotopic labeling of lipoprotein triglyceride with radioactive triolein.

A procedure has been developed for the exogenous isotopic labeling of triglyceride-rich lipoproteins (chylomicrons and very low density lipoproteins) using high specific activity radioactive triglyceride in the presence of aqueous dimethyl sulfoxide. The labeled product lipoproteins showed unchanged chemical and physical properties. When the particles had also been labeled biologically by incorporation of unesterified fatty acids into the triglycerides of lipoproteins secreted by liver or intestine, both endogenous and exogenous labels were removed at the same rates in the isolated perfused heart and liver or in intact or functionally hepatectomized rats. These experiments additonally indicated that the triglyceride fatty acid composition of chylomicrons and very low density lipoproteins was unchanged during triglyceride depletion in the peripheral tissues. Using such labeled lipoproteins it has been shown that uptake of remnant lipoprotein cholesteryl ester and triglyceride by the liver is simultaneous. The labeling procedure described should prove suitable for kinetic studies of the disposition of the various lipoprotein non-polar ('core') lipids.     

Changes in lipid contents and fatty acid compositions in ovine corpora lutea during the estrous cycle and early pregnancy

Changes in lipid contents and fatty acid compositions of each lipid fraction were examined in corpora lutea from 34 unmated ewes between Days 8 and 16 of the estrous cycle and from 6 ewes at Day 16 of pregnancy. Four patterns were observed during advancement of the estrous cycle. Luteal concentrations of free cholesterol and triglyceride (neutral lipids) increased between Days 14 and 16, during luteal regression, in a manner approximated by exponential functions of time, whereas luteal concentrations of phospholipid (polar lipids) increased and then decreased between Days 8 and 16 in a manner approximated by a sin function of time. Likewise, within the various lipid class component fatty acids, changes in palmitic acid weight percentages were approximated by sin functions of time, whereas arachidonic acid weight percentages increased between Days 14 and 16 in a manner approximated by exponential functions of time. Pregnancy either inhibited or reversed the changes in luteal lipid profiles, especially arachidonic acid percentages, between Days 14 and 16 of the estrous cycle. Luteal lipid profiles of corpora lutea from Day 16 pregnant sheep approximated lipid profiles of corpora lutea recovered from sheep between Days 12 and 14 of the estrous cycle. Comparison of luteal lipid profiles after tissue incubations at either 0 or 37 degrees C for 2 h revealed an effect of reproductive status on fatty acid metabolisms at Day 16. Changes observed in luteal lipid contents and fatty acid compositions during advancement of the estrous cycle represent aspects of lutein cell maturation and impending senescence that can be inhibited or reversed by pregnancy.     

Nutritional evaluation of structured lipid containing omega 6 fatty acid synthesized from coconut oil in rats

Coconut oil is rich in medium chain fatty acids, but deficient in polyunsaturated fatty acids (PUFA). Structured lipids (SL) enriched with omega 6 PUFA were synthesized from coconut oil triglycerides by employing enzymatic acidolysis with free fatty acids obtained from safflower oil. Rats were fed a diet containing coconut oil, coconut oil-safflower oil blend (1:0.7 w/w) or structured lipid at 10% levels for a period of 60 days. The SL lowered serum cholesterol levels by 10.3 and 10.5% respectively in comparison with those fed coconut oil and blended oil. Similarly the liver cholesterol levels were also decreased by 35.9 and 26.6% respectively in animals fed structured lipids when compared to those fed on coconut oil or the blended oil. Most of the decrease observed in serum cholesterol levels of animals fed structured lipids was found in LDL fraction. The triglyceride levels in serum showed a decrease by 17.5 and 17.4% while in the liver it was reduced by 45.8 and 23.5% in the structured lipids fed animals as compared to those fed coconut oil or blended oil respectively. Differential scanning calorimetric studies indicated that structured lipids had lower melting points and solid fat content when compared to coconut oil or blended oils. These studies indicated that enrichment of coconut oil triglycerides with omega 6 fatty acids lowers its solid fat content. The omega 6 PUFA enriched structured lipids also exhibited hypolipidemic activity.     

Differential changes in the fatty acid composition of the main lipid classes of chick plasma induced by dietary coconut oil

For a better understanding of the hyperlipidemic function of saturated fat, we have studied the comparative effects of diet supplementation with 10 and 20% coconut oil on the main lipid classes of chick plasma. Changes in fatty acid composition of free fatty acid and triglyceride fractions were parallel to that of the experimental diet. Thus, the increase in the percentages of 12:0 and 14:0 acids may contribute to the hypercholesterolemic effects of coconut oil feeding. Plasma phospholipids incorporated low levels of 12:0 and 14:0 acids whereas 18:0, the main saturated fatty acid of this fraction, also increased after coconut oil feeding. The percentage of 20:4 n-6 was higher in plasma phospholipids than in the other fractions and was significantly decreased by our dietary manipulations. Likewise, minor increases were found in the percentages of 12:0 and 14:0 acids in plasma cholesterol esters. However, the percentage of 18:2 acid significantly increased after coconut oil feeding. Our results show a relationship between fatty acid composition of diets and those of plasma free fatty acid and triglyceride fractions, whereas phospholipids and cholesterol esters are less sensitive to dietary changes.     

The effect of a combined dietary treatment with cholesterol and cholic acid on the lipid metabolism of geese at low or high choline concentrations

A previous study demonstrated that a dietary treatment of young geese with cholesterol and cholic acid raises lipid concentrations in the liver. The present study was carried out to investigate whether such a lipid accumulation caused by those hyperlipidemic compounds can be intensified by low dietary choline concentrations. Therefore, 38 eight‐week old geese were divided into four groups of 9 or 10 animals each and received a basal diet poor in choline which consisted predominately of maize and soy protein isolate over a period of 8 weeks. Treatment factors were supplementation of diets with cholesterol and cholic acid (0 vs. 5 g of cholesterol and cholic acid each per kg) and supplementation of choline chloride (0 vs. 1.5g/kg). Final body weights as well as carcass weights were neither influenced significantly by dietary treatment with cholesterol and cholic acid nor by low dietary choline concentrations. However, feeding diets supplemented with cholesterol and cholic acid markedly increased liver weights (two‐fold), hepatic triglyceride (3.7‐fold) and cholesterol (12‐fold) concentrations and percentages of monounsaturated fatty acids at the expense of saturated and polyunsaturated fatty acids in the liver. In geese fed diets with cholesterol and cholic acid, insufficient choline supply did not intensify, but even slightly reduced hepatic lipid accumulation. Geese fed diets with cholesterol and cholic acid exhibited markedly increased levels of cholesterol, triglycerides and phospholipids in plasma and very low‐density lipoproteins, regardless of the choline supply. Muscle tissue of geese fed diets supplemented with cholesterol and cholic acid exhibited also increased concentrations of triglycerides and cholesterol whereas the fatty acid composition of muscle lipids remained unchanged. Among geese without hyperlipidemic treatment, concentrations of triglycerides in plasma and very low‐density lipoproteins as well as the concentrations of phosphatidylcholine in liver and muscle tissue were not reduced by low dietary choline concentrations. Therefore, it is suggested that those animals were able to synthesize endogenous sufficient choline.     

Dietary saturated fatty acid content affects lymph lipoproteins: studies in the rat

We examined effects on intestinal absorption of cholesterol and triglycerides and intestinal lipoprotein formation by feeding rats diets in which saturated fatty acids (palmitic plus stearic) comprised 78%, 68%, 48%, or 38% of triglyceride fatty acids. Absorption into lymph of radiolabeled cholesterol was proportional to triglyceride absorption. The rates of absorption of these lipids were related inversely to the % saturated fatty acids fed. The distribution of newly absorbed cholesterol and triglyceride into intestinal lipoproteins differed. With increasing cholesterol absorption more was recovered in very low density lipoproteins in contrast to the appearance preferentially in chylomicrons of larger quantities of fatty acid. Lymph lipid content did not reflect a consistent pattern in relation to the experimental diet fed. The fatty acid composition of triglyceride-rich lymph lipoproteins resembled the diet closely. One-quarter of the intestinal lymph particles from rats fed the highly saturated diets was flattened and polygonal as judged by electron microscopy if cooled to room temperature; whereas with the same diets, particles collected and isolated at 37 degrees C were round. Proportions of A-I and C apolipoproteins in triglyceride-rich intestinal particles varied inversely; apoA-I increased as fat/cholesterol absorption was greater. Diet-induced alterations in plasma lipoproteins and increased circulating triglycerides in this study in rats were unrelated to the variations in intestinal absorption or lymph lipoprotein formation.     

Lipid composition of the vascular system during infancy, childhood, and young adulthood

The object of this study was to determine the changes in lipid composition that occur in blood vessels from infancy to young adulthood. Analyses included levels of total cholesterol, total triglyceride, phospholipid, and cholesteryl ester fatty acids, and the distribution of saturated and unsaturated fatty acids. Triglyceride, total and monoenoic fatty acids, and linoleic acid were lower in the ascending, thoracic, and abdominal aorta than in the pulmonary artery and inferior vena cava. Phospholipids and arachidonic acid were higher in aortic segments than in the other two vessels. Aortic lipids showed significant changes with increasing age: total cholesterol and total fatty acids decreased from <1 wk to 5 yr, then increased to 22 yr of age. Triglycerides decreased whereas cholesteryl esters increased from 10 to 22 yr of age. Saturated fatty acids decreased from 1 wk to 10 yr, then remained relatively constant. Linoleic acid (3.7-9.8% of total fatty acids) and arachidonic acid (15.8-21.7%) both increased with age; the increase in cholesteryl linoleate was highly significant. After 10 yr of age, total cholesterol and total fatty acids were significantly higher in abdominal than in ascending and thoracic segments of aorta.