Food effect on the physiological condition of the mussel Perna viridis (Bivalvia: Mytilidae), using the RNA/DNA ratio

The green mussel, Perna viridis, became widespread in the northern coast of Sucre State since its arrival to Venezuela in 1993. RNA/DNA and Protein/DNA ratios were used to study the effect of starvation on its instantaneous growth. The mussels were collected in La Esmeralda and Chacopata, acclimatized in the laboratory for four weeks and maintained for another six weeks in two groups: one fed ad libitum and another without food (this later group was later fed for two additional weeks). Protein (colorimetric method), and nucleic acid concentrations (RNA and DNA, fluorometric method with ethidium bromide) were measured in adductor muscle, digestive gland and gills. The instantaneous growth was assessed using RNA/DNA and Protein/DNA rations. These indexes were always higher in the fed organisms. Animals from Chacopata were in better physiological condition that those from La Esmeralda during the abstinence time (six weeks). Muscle was the best tissue to determine instantaneous growth. The RNA/DNA ratio is a reliable index to determine the physiological condition and instantaneous growth of this species.     

The transfer of fatty acids across the sheep placenta

Maternal and fetal plasma concentrations of free fatty acids, triacylglycerols and phospholipids and the profile of their fatty acids were measured in three catheterized and unanaesthetized sheep. Fetal concentrations of all three lipid fractions were low and did not correlate with maternal concentrations. There were no measurable umbilical venous-arterial differences. Linoleic acid concentrations were low in both mother and fetus. The fatty acid composition of fetal adipose tissue, liver, lung and cerebellum of five animals was analysed. Again linoleic acid levels were very low, but phospholipids contained 2-8% arachidonic acid. [14C] linoleic acid and [3H] palmitic acid were infused intravenously into three ewes. Only trace amounts of labelled fatty acids were found in fetal plasma and these were confined to the free fatty acids. 14C-label was incorporated into fetal tissue lipids, but most of this probably was due to fetal lipid synthesis from [14C] acetate or other water-soluble products of maternal [14C] linoleic acid catabolism. It is concluded that only trace amounts of fatty acids cross the sheep placenta. They are derived mainly from the maternal plasma free fatty acids and might just be sufficient to be the source of the small amounts of essential fatty acids found in the lamb fetus, but are insignificant in terms of energy supply or lipid storage.     

Characterization of the total lipid and fatty acid composition of rat olfactory mucosa

Phospholipid accounted for 81% (by weight) of the total lipid of rat olfactory mucosa. Phosphatidylcholine (46% of total phospholipids) and phosphatidylethanolamine (26%) were the predominant phospholipids. Phosphatidylinositol (8%), sphingomyelin (6%), and phosphatidylserine (7%) were the next most abundant phospholipids, with cardiolipin (4%) and phosphatidic acid (1%) present in lesser amounts. Only trace amounts of the polyphosphoinositides, phosphatidylinositol monophosphate, and phosphatidylinositol bisphosphate were detected. Sterol was the major neutral lipid present (83% of the total neutral lipid mass) with lesser amounts of triacylglycerols (7%), steryl esters (6%), free fatty acids (4%), and diacylglycerols (1%). Monoacylglycerols were detected only in trace amounts. The sterol to phospholipid ratio was 0.39:1. Most of the phospholipids of the olfactory mucosa showed a high polyunsaturated fatty acid content, with the arachidonic acid (20:4) and docosahexaenoic acid (22:6) residues predominating. The fatty acids in sphingomyelin, however, were almost totally saturated and included the 24:0 and 24:1 residues, which were not detected in other phospholipids. Polyunsaturated fatty acids accounted for less than 25% of the total fatty acid of any individual neutral lipid and comprised largely linoleic and arachidonic acids. The results are discussed in relation to the putative role of lipids in olfactory signal transduction.     

Lipid and fatty acid composition of the fat body during the female reproductive cycle of Labidura riparia (Insecta Dermaptera)

During the reproductive cycle of the female Labidura riparia, cytological observations show cyclical modifications of lipid droplets in the periovarian adipocyte. Fat body lipids and their constitutive fatty acids are analyzed. The lipids are predominantly triacylglycerols, which increase after adult ecdysis during vitellogenic and non-vitellogenic periods. Small amounts of diacylglycerols and phospholipids are found. Diacylglycerols increase during vitellogenesis and decrease during the non-vitellogenic period. Cytological modifications of lipid droplets are probably related to diacylglycerol fluctuations. Gas-liquid chromatography of fatty acid methyl esters shows oleic acid to be the predominant fatty acid in total lipids and triacylglycerols; unsaturated acids are approximately twice as abundant as saturated acids all along the reproductive cycle. Fatty acid composition of diacylglycerols and phospholipids differs from triacylglycerols and total lipids composition. Palmitic, stearic, oleic and linoleic acids represent the major fatty acids; their relative amounts vary during the different periods of the reproductive cycle. The correlations between fat body lipid changes and ovarian development were discussed and compared with observations made on other insect species. Accepted: 23 April 1997     

Changes in plasma fatty acids indicate change in nutritional status in developing Weddell seal pups

The concentrations and the fatty acid compositions (weight percent) of three plasma lipid fractions (phospholipids, cholesteryl esters, and triacylglycerols) were examined in five Weddell seal pups through suckling, the post-weaning fast and periods of independent foraging. The principal plasma fatty acids in Weddell seal pups during suckling were the same as those previously reported for milk samples collected from lactating Weddell seals. In contrast to the stable milk fatty acid composition suggested by the previous study, significant changes in the fatty acid composition of plasma lipids occurred during suckling. These included an increase in the weight% of 20:4(n-6) and 18:0 in phospholipids, an increase of 20:4(n-6) in cholesteryl esters, and an increase of 20:1(n-9) and a decrease of 20:5(n-3) in triacylglycerols. Weaning and the subsequent fasting period were accompanied by a dramatic drop in the plasma concentration and 14:0 content of triacylglycerols and by marked decrease and increase in the weight% of 20:1(n-9) and 20:5(n-3), respectively, in this lipid fraction. Weight% of 14:0 in triacylglycerols and/or plasma concentration of triacylglycerols clearly distinguish post-weaning from suckling. However, fasting versus foraging pups could not be clearly distinguished. Received: 7 October 1996 / Accepted: 20 May 1997     

In vitro and in vivo synthesis of long-chain fatty acids from (1-14C) acetate in the renal papillae of rats.

1. The relationship between the rate of [1-14C] acetate incorporation into the fatty acids of renal papillary lipids and the acetate concentration in the medium has been measured. 2. [1-14C] acetate was incorporated mainly into fatty acids of phospholipids and triacylglycerols. Only a few per cent of the radioactivity was found in the free fatty acid fraction. 3. The major part of the [1-14C] acetate was found to be incorporated by a chain elongation of prevalent fatty acids. The major component of the poly-unsaturated fatty acids in triacylglycerols and the major product of fatty acid synthesis from [1-14C] acetate in vitro was demonstrated by mass spectrometry to be docosa-7,10,13,16-tetraenoic acid. 4. The radioactivity of docosa-7,10,13,16-tetraenoic acid accounted for 40% of total radioactivity in triacylglycerol fatty acids (lipid droplet fraction) and 20% of total radioactivity in membrane phospholipid fatty acids.     

Octadecenoic Fattv Acids and their Association with Hemolysis in Malaria

SYNOPSIS. Octadecenoic fatty acids have been implicated in prehemolytic and hemolytic phenomena associated with malaria. Oleic [18:1 (n-9)] and cis-vaccenic [18:1 (n-7)] acids were found and quantified in the major neutral and phospholipids of the erythrocytes and plasmas of normal and Plasmodium lophurae-infected ducks, and in the parasite itself. The octadecenoic fatty acids were elevated over normal values in the major phospholipid classes of infected erythrocytes, in the erythrocyte-specific alkoxy phosphatidylethanolamine of infected erythrocytes, and in the plasma unesterified fatty acids, triacylglycerols, cholesterol esters and phosphatidylcholine of infected ducklings. Oleic acid was the major fatty acid of P. lophurae (33% total lipid fatty acids). Theoretical considerations of octadecenoic fatty acid modifications of erythrocyte membrane structure and function in malaria are discussed.     

Seasonal changes in lipid classes and fatty acid composition in the digestive gland of Pecten maximus

Seasonal variations in lipid classes and fatty acid composition of triacylglycerols and phospholipids in the digestive gland of Pecten maximus were studied over a period of 16 months. Acylglycerols predominated (19-77% of total lipids), in accordance with the role of the digestive gland as an organ for lipid storage in scallops. Seasonal variations were mainly seen in the acylglycerol content, while phospholipids (2.5-10.0% of total lipids) and sterols (1.9-7.4% of total lipids) showed only minor changes. The most abundant fatty acids were 14:0, 16:0, 18:0, 16:1(n-7), 18:1(n-9), 18:1(n-7), 18:4(n-3), 20:5(n-3) and 22:6(n-3) and these showed similar seasonal profiles in both, triacylglycerol and phospholipid fractions. In contrast to the phospholipid fraction, the triacylglycerol fraction contained more 20:5(n-3) than 22:6(n-3). In three phospholipid samples we noted a high percentage of a 22-2-non-methylene-interrupted fatty acid, previously described to have a structural role in several bivalve species. The main polyunsaturated fatty acids displayed important seasonal variations parallel to those of the acylglycerols, suggesting good nutritional conditions. A positive correlation existed between the level of saturated fatty acids and temperature, whereas the levels of polyunsaturated fatty acids correlated negatively with temperature.     

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.     

Changes in the lipid and fatty acid composition of hemolymph and ovaries during the reproductive cycle of Labidura riparia

Lipid metabolism was investigated during the reproductive cycle of Labidura riparia (Pallas). The lipid classes and their constitutive fatty acids present in hemolymph and ovaries were measured using thin‐layer chromatography and gas‐liquid chromatography. In the hemolymph, total lipids increase steadily from the previtellogenic period to vitellogenic arrest. These lipids are predominantly diacylglycerols and phospholipids. In the ovaries, total lipids increase during vitellogenesis then decrease during the vitellogenesis arrest period. The major lipids are triacylglycerols, followed by phospholipids. In both hemolymph and ovaries, all lipid classes contained variable proportions of seven main fatty acids: the saturated fatty acids myristic acid (14:0), palmetic acid (16:0), and stearic acid (18:0); the monounsaturated fatty acids palmitoleic acid (16:1) and oleic acid (18:1); and the polyunsaturated fatty acids linoleic acid (18:2) and linolenic acid (18:3). Unsaturated fatty acids predominate throughout the reproductive cycle. The percentage compositions of total and triacylglycerol fatty acids do not change markedly during the reproductive cycle in hemolymph nor in ovaries, with 18:2, 18:1 and 16:0 fatty acids being the major components. However, for diacylglycerols and phospholipids, the proportions of fatty acids vary systematically. For phospholipids during the vitellogenesis period, 18:2 increases considerably whereas other fatty acids decrease; for diacylglycerols, these fatty acids vary in the reverse way.     

Essential fatty acid uptake and esterification in primary culture of rat hepatocytes

Primary cultures of adult rat hepatocytes were used to compare the uptake and esterification of essential polyunsaturated fatty acids (18:2, 20:3 and 20:4 of the n-6 series) with those of palmitic and oleic acids. The uptake of unesterified fatty acids was linearly related to the free fatty acid/albumin molar ratio for 14 h and did not depend on the unbound free fatty acid level. Whatever the initial free fatty acid/albumin molar ratio, it dropped to 0.5 +/- 0.1 mM after 14 h, thus showing that hepatocytes have a high capacity for clearing free fatty acids from the medium at high free fatty acid/albumin molar ratios. The free fatty acid uptake become saturable when the free fatty acid and albumin concentrations were raised and the free fatty acid/albumin ratio remained constant. This strongly suggests that albumin-hepatocyte interaction mediates free fatty acid uptake. This uptake was identical whatever the fatty acid tested and did not depend on the relative amounts of fatty acids when they were added simultaneously. Triacylglycerol accumulation and synthesis, monitored by labelled fatty acids, were related to the free fatty acid/albumin molar ratio and exhibited no specificity for the series of fatty acids tested. Triacylglycerols were enriched in all the fatty acids tested by up to 60%, and fatty acid incorporation into diacylglycerols and triacylglycerols reflected the free fatty acid composition of the medium. By contrast, neither the level nor the synthesis of phospholipids varied with free fatty acid/albumin, but the rate of phospholipid turnover depended on the fatty acids tested. Accumulation of these acids was smaller in phospholipids than in triacylglycerols. When linoleic and arachidonic acids were added together, phospholipids (especially phosphatidylethanolamine and phosphatidylinositol) were more enriched in arachidonic acid than triacylglycerols. This might be due to the specificity for fatty acid of the enzymes involved in phospholipid metabolism.     

Effect of microalgal diets and commercial wheatgerm flours on the lipid profile of Ruditapes decussatus spat

The influence of both the lipid composition of microalgal diets and commercial flours on the lipid classes and fatty acids of Ruditapes decussatus spat was studied. These aspects of the nutritional value of the diets were discussed in relation to the growth of the spat. Four diets were tested; Diet A, composed of 100% of the daily food ration of microalgae; Diet B, composed of 100% of wheatgerm; Diet C, composed of 50% of microalgae and 50% of wheatgerm; and Diet D, composed of 25% of microalgae and 75% of wheatgerm. The microalgal cells present a higher lipid content than that for wheatgerm. Tahitian Isochrysis cells have phospholipids and triacylglycerols as majority lipids, whereas in the wheatgerm particles, the lipids more abundant are triacylglycerols. Fatty acid content was higher in the microalgal cells than in the wheatgerm particles. The n-3 fatty acids were the most abundant acids in the microalgae, whereas the n-6 fatty acids were in the wheatgerm. The n-3 PUFA were not detected in wheatgerm. Phospholipids were the main lipids present in the clam spat, followed by triacylglycerols. Other lipid classes, detected in significantly lower amounts, included free fatty acids, sterols, and sterol ester + waxes. The composition of fatty acids in the spat was influenced by the fatty acid composition of the diet. Highest spat growth rates were observed with those diets that present a higher phospholipid/triacylglycerol relation. A negative correlation in the relation n-6/n-3 vs. growth has also been observed, with better growth rates in diets with a lower ratio. If the fatty acid 20:5n-3 and 22:6n-3 considered "essential" for marine animals were not present in the diet, they were not present in the spat either. Desaturation and elongation capabilities of R. decussatus spat were also discussed.     

Studies on furan fatty acids of salmon roe phospholipids

Mature salmon roe lipids were found to consist of triacylglycerols (63%), phospholipids (30%), sterols (4.2%), steryl esters (0.7%), and other minor components. In the steryl esters and phospholipids, furan fatty acids were detected instead of the triacylglycerols of the testes lipids in male fish. The representative 12,15-epoxy-13,14-dimethyleicosa-12,14-dienoic acid (F6) amounted to 3.8% and 0.6% of the total fatty acids in each fraction, respectively. However, the absolute amount of the acid in the phospholipid was much more than that contained in the steryl esters. The characteristic distribution of the furan acids found in the phospholipids was common to the steryl esters in the liver. Large amounts of furan acids were contained in phosphatidylcholine (PC) rather than in phosphatidylethanolamine. For positional analysis of furan fatty acids in PC, furan-containing species in the molecule were concentrated fourteenfold by using selective hydrogenation and repeated silica gel column chromatography. A series of furan fatty acids in PC was found to be exclusively linked to the sn-1 position. The amount of the acids in the roe exclusively linked to the sn-1 position. The amount of the acids in the roe phospholipids was comparable with that in the testes triacylglycerols. The physiological roles of furan fatty acids are discussed.     

Minor amounts of plasma medium-chain fatty acids and no improved time trial performance after consuming lipids.

Medium-chain triacylglycerols (MCT) have a potential glycogen-saving effect during exercise due to rapid hydrolysis and oxidation. However, studies comparing intake of carbohydrates (CHO) plus 80-90 g MCT with intake of CHO alone have revealed different results. The present study tested performance after consumption of specific structured triacylglycerol, consisting of a mixture of medium-chain fatty acids and long-chain fatty acids, to prevent the adverse effects observed by MCT (pure medium-chain fatty acids) regarding gastrointestinal distress. Seven well-trained subjects cycled 3 h at 55% of maximum O2 uptake during which they ingested CHO or CHO plus specific structured triacylglycerols. Immediately after the constant-load cycling, the subjects performed a time trial of approximately 50-min duration. Breath and blood samples were obtained regularly during the experiment. Fatty acid composition of plasma triacylglycerols, fatty acids, and phospholipids was determined. Performance was similar after administration of CHO plus specific structured triacylglycerol [medium-, long-, and medium-chain fatty acid (MLM)] compared with CHO (50.0 +/- 1.8 and 50.8 +/- 3.6 min, respectively). No plasma 8:0 was detected in the plasma lipid classes, but the amount of phospholipid fatty acids was significantly higher after CHO+MLM compared with CHO intake. The lacking time trial improvement after intake of medium-chain fatty acids might be due to no available 8:0 in the systemic circulation. A higher level of plasma phospholipid fatty acids in the CHO+MLM compared with the CHO group was probably due to endogenous phospholipid release into chylomicrons.     

Influence of the light regimen on the circadian rhythm of serum lipids in the laboratory rat

Young male rats of a conventional Wistar breed were adapted for several weeks (3-6) to a 12:12 h light:dark (7 a.m. - 7 p.m., 7 p.m. - 7 a.m.) regimen (LD), to inversion of this standard regimen (DL), to continuous darkness (DD) or to continuous light (LL). After adaptation, groups of animals were killed at 3-hour intervals during the day and the basic lipid fractions were determined in their serum. Under the standard light regimen the cosinor test demonstrated a rhythm in all the indicators (triacylglycerols, total cholesterol, phospholipids) except for non-esterified fatty acids. When the regimen was inverted (DL), the peaks of the circadian non-esterified fatty acid and triacylglycerol curves shifted to the antiphase. The acrophases of "free-running" serum lipid rhythm under the DD regimen of the standard regimen rhythms differed in the case of cholesterol and phospholipids. In the case of triacylglycerols and phospholipids there was disagreement between the DD and LL regimen curves. With reference to the localization of the acrophase under the DD and LD regimens it was assumed that the influence of the light regimen on the synchronization of circadian rhythms is small in the case of serum non-esterified fatty acids and triacylglycerols and that it is greater in the case of serum cholesterol and phospholipids.     

Influence of the fatty acid composition of lipids in chylomicron remnants derived from fish or corn oil on the lipid profile of cultured rat hepatocytes

The aim of this work was to characterise the lipid and fatty acid composition of chylomicron remnants enriched in n-3 or n-6 polyunsaturated fatty acids (PUFA) and to investigate their influence on the fatty acid profiles of the lipids of rat hepatocytes cultured in monolayers. Chylomicrons were prepared from the lymph collected from the thoracic duct of rats given an oral dose of fish or corn oil (high in n-3 and n-6 PUFA, respectively), and remnants were prepared in vitro from such chylomicrons using rat plasma containing lipoprotein lipase. The fatty acids predominating in the oils abounded also in their respective chylomicrons and remnants, especially in triacylglycerols. Chylomicrons as well as remnants contained small amounts of phospholipids and long-chain PUFA that were minor in, or absent from, the dietary oils, evidently provided by the intestinal epithelium. The incubation of hepatocytes for 6 h, with either n-3 or n-6 PUFA-rich remnants (0.25-0.75 mM triacylglycerol) resulted in a dose-dependent increase in the amount of triacylglycerols and phospholipids in the cells, which was not affected further by increasing the incubation time to 19 h. Whereas hepatocyte triacylglycerols mostly incorporated the PUFA predominating in each remnant type, the fatty acid profile of cell phospholipids was virtually unchanged. In addition, irrespective of whether they were enriched in n-3 or n-6 PUFA, remnants promoted a relative decrease in the amount of cholesteryl esters, a minor hepatocyte lipid class poor in PUFA. The results demonstrate that the hepatocyte fatty acid profile is modulated in a lipid-class specific way by the amount and type of dietary PUFA delivered to cells in chylomicron remnants.     

Unusual fatty acids in turkeys fed a diet containing "Toprina". I. Composition of the higher fatty acids in "Toprina", the diet, feces and blood]

Totals lipids (TL) phospholipids (PL) and fatty acid composition of TL and PL (the latter in blood only) were estimated in Candida lipolytica cultivated on n-alkanes by industrial method ("Toprina"), in 0%, 10% and 15% "Toprina" diets and in faeces and blood of turkeys, males and females, fed these diets. With increasing concentrations of dietary "Toprina" phospholipids and 15:0 and 17:0 fatty acids increased, 17:1 and 17:2, typical of the product, appeared and increased in diets and blood. Other lipid and fatty acids values were not affected by dietary yeast.     

Effect of sex and bezafibrate on incorporation of blood borne palmitate into lipids of rat liver nuclei

The aim of the present study was to investigate whether lipid metabolism in the nuclei is affected by changes in the metabolism of free fatty acids in the liver. The experiments were carried out on 3 groups of rats: 1 - control-male, 2 - female, and 3 - male, treated with bezafibrate (a peroxisome proliferator). The rats received ¹⁴C-palmitic acid intravenously. Thirty min later liver samples and blood from the abdominal aorta were taken. The liver nuclei were isolated in sucrose gradient. Lipids were extracted from the nuclei and the liver homogenate and subsequently separated into the following fractions: phospholipids, mono-, di- and triacylglycerols, free fatty acids, cholesterol and cholesterol esters. The radioactivity of each fraction was counted. Furthermore, the content of free fatty acids and the fatty acid binding proteins was measured. It was found that radioactivity was present in each lipid fraction obtained from the liver homogenate and from the nuclei. In the female group, the total radioactivity of lipids in the liver homogenate was lower, whereas in the nuclei it was higher in comparison to the male group. The reduction in the radioactivity in the liver was mostly accounted for by decreased radioactivity in the fraction of triacylglycerols and phospholipids. In the nuclei, the radioactivity of the fraction of phospholipids, free fatty acids and diacylglycerols was elevated. Bezafibrate did not affect the total radioactivity of lipids in the liver and reduced it in the nuclei. In the liver, the drug increased radioactivity mostly in the fraction of phospholipids and reduced it mainly in the fraction of triacylglycerols. In the nuclei, the radioactivity of each lipid fraction examined was reduced. The content of the fraction of free fatty acids in the liver and in the nuclei in the female and in the bezafibrate-treated groups did not differ from the respective value in the control group. The content of fatty acid binding proteins in the nuclei of the female and bezafibrate-treated groups increased in parallel to the elevation in their content in the cytosol. It is concluded that the female sex hormones and bezafibrate influence the transport of selected lipids into the nuclei. The effects seem to be a consequence of the action of these factors directly on the nucleus.     

Studies on (Na+ + K+)-activated ATPase. XLIX. Content and role of cholesterol and other neutral lipids in highly purified rabbit kidney enzyme preparation

(1) The neutral lipids and the free and bound fatty acids of a highly purified (Na+ + K+)-ATPase preparation from rabbit kidney outer medulla have been analysed. (2) On a dry weight basis, the total lipid content is nearly the same as the total protein content, and consists for 66% of phospholipids and for 34% of neutral lipids and free fatty acids. In the latter category cholesterol is the main component (71%). (3) On a molar basis the enzyme preparation contains 382 mol phospholipids, 67 mol free fatty acids, 9, 16 and 12 mol mono-, di- and triacylglycerols, 249 and 19 mol free and esterified cholesterol per mol enzyme. (4) The fatty acid composition of each lipid and of the free fatty acid fraction, present in the enzyme preparation, is reported. (5) All cholesterol and part of the phospholipids can be removed by hexane extraction, leaving 66% of the (Na+ + K+)-ATPase activity. Oxidation of all cholesterol to cholest-4-en-3-one by cholesterol oxidase leaves 85% of the (Na+ + K+)-ATPase activity. These results indicate that cholesterol is not essential for (Na+ + K+)-ATPase activity.     

Distribution of dietary trans-octadecenoate among acyl-CoA and other lipid fractions of rat liver and heart

Groups of rats were fed diets containing 10% of either corn oil, partially hydrogenated soybean oil, or a mixture of the two. The partially hydrogenated oil contained a high level of trans-octadecenoate and a low level of linoleate, and all diets were adjusted to contain similar levels of cis-octadecenoate. The fatty acid compositions of five tissue lipid fractions from liver and heart (non-esterified fatty acids, acyl-CoA, diacylglycerols, triacylglycerols and phospholipids) were analyzed to measure the effect of the dietary supply on the accumulation of trans-octadecenoates and other fatty acids at different steps of glycerolipid synthesis. Although trans-octadecenoate was increased in all of the lipid fractions when the dietary supply was increased, the accumulation did not exceed 15% of the acyl chains in any of the lipid pools even when the dietary trans acid accounted for 46% of the fatty acids supplied in the diet. The trans-octadecenoate accumulated in a similar manner in the lipids of both liver and heart, and the amounts found in the acyl-CoA esters of both tissues were relatively low compared to the diet. A high dietary supply of trans-octadecenoate appeared to diminish the relative content of stearate in the acyl-CoA and phospholipid fractions. The level of cis-octadecenoate maintained in tissue phospholipids was similar to that in the acyl-CoA fractions, whereas the trans-octadecenoate content in phospholipids more closely resembled that in the diacylglycerols. Normal proportions of arachidonate were maintained in the tissue phospholipids during high intake of trans acids, even though lower levels were observed in the acyl-CoA and diacylglycerols of liver.