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PubMed1983

Biochemical and electron microscope radioautographic study of intestinal absorption of tritiated palmitic and oleic acids in control and actidione-cycloheximide-treated rats.

Intestinal absorption of tritiated palmitic and oleic acids was investigated in control and actidione-cycloheximide-treated rats. Pancreatic juice was collected and 24 hr later an intestinal loop was cannulated in situ. A 90 mumole-lipid emulsion composed of an equimolar mixture of monopalmitin, palmitic and oleic acids with bile was infused with either 3H-labeled palmitic or oleic acid. After 15 or 30 min biochemical analysis was carried out to follow the uptake and the transfer of the labeled fatty acids. Mucosa was removed for both biochemical analysis of lipid classes and the ultrastructural or radioautographic electron microscope study depending on the radioactive activity. Following actidione-cycloheximide treatment, the uptake of both fatty acids decreased, but the amount of lipids in the mucosa greatly increased, while amount of the reesterification of fatty acids in the mucosa diminished. Consequently the amount of infused palmitic acid which was transferred in 15 min decreased from 36% in the absence of treatment to 4.6% when treatment was used. The corresponding figures for oleic acid are 70% and 20.9%. Unstructured lipids were in the intercellular spaces, indicating that a cytotoxic effect had occurred which produced a defect in the lipoprotein particle organization. The Golgi complex, in the final step of the chylomicron synthesis before exocytosis, showed low level of radioautographic reaction indicating less participation by the complex in lipid transfer. The various processes which were inhibited during long-chain fatty acid absorption from the luminal area to the Golgi complex included fatty acid binding by proteins, enzymatic acylation and esterification, apoprotein participation. This inhibition explains why long-chain fatty acid absorption was greatly impaired. Moreover, our observations compared with those obtained during decanoic acid absorption, particularly our radioautography based observations, emphasize the important role of the Golgi complex which requires intense membrane turnover during lipid absorption.

Animals↗
PubMed1984

Hepatic palmitate metabolism in fasting Zucker rats: effect of lactate on partitioning.

Hepatocytes were isolated from 48-h fasted lean and obese Zucker rats and incubated with [1-14C] palmitate. The partitioning of fatty acids to oxidation and esterification products and the effect of lactate or glucose on this partitioning were studied. With palmitate as the only substrate, the cells from the lean rats oxidized 80% of the palmitate that was metabolized compared with only 35% oxidation in the cells from the obese rats. Thus fatty acid esterification remained the predominate pathway of palmitate metabolism in the hepatocytes from fasting obese rats. The addition of lactate to the cells from the lean rats decreased oxidation and increased esterification to levels similar to those in the obese rat hepatocytes. Glucose had similar effects on esterification in lean rat hepatocytes but was less potent than lactate. The cells from the obese rats were insensitive to the addition of lactate or glucose. These studies indicate that the inability of hepatocytes from obese rats to induce ketogenesis from exogenous fatty acids after a 48-h fast and their insensitivity to added lactate or glucose may be related to the availability of endogenous energy sources in the obese liver that can be oxidized and thus inhibit ketogenesis and support fatty acid esterification.

Animals↗
PubMedDate not supplied

Regional cerebral palmitate incorporation following transient bilateral carotid occlusion in awake gerbils.

[14C]Palmitate was injected intravenously in awake gerbils at various times after 5 minutes of bilateral carotid artery occlusion or a sham operation. Regional rates of incorporation of plasma palmitate into the hippocampus and other regions of the anterior circulation were determined relative to the mean rate of incorporation into regions of the posterior circulation using quantitative autoradiography and a ratio method of analysis. One day after bilateral carotid occlusion, relative palmitate incorporation was elevated significantly by 16% in the CA4 pyramidal cell layer and by 20% in the dentate gyrus of the hippocampus compared with sham-operated gerbils. At 3 days, significant elevations of this magnitude were found in the CA3 and CA4 cell layers, whereas relative incorporation was reduced by 26% in the CA1 pyramidal cell layer. At 7 days, the only significant difference from control was a 15% elevated incorporation in the CA3 pyramidal cell layer. Histologic examination indicated substantial cell death in the CA1 pyramidal layer at 3 days, with extensive glial reaction and phagocytic invasion at 7 days. Our results suggest that the turnover of palmitate-containing lipids is reduced in the CA1 layer of the gerbil hippocampus but that lipid synthesis is stimulated in hippocampal regions (CA3, CA4, dentate gyrus) affected by but recovering from transient bilateral carotid occlusion.

Animals↗
PubMed1986

Palmitate uptake by hepatocyte monolayers. Effect of albumin binding.

The uptake of 14C-palmitate by rat liver cell monolayers is depressed by binding of the fatty acid to albumin. When the uptake flux is divided by the concentration of free palmitate in the bathing medium, however, the resulting clearance is approximately 14 times greater in the presence of albumin than in its absence. These findings are not accounted for by the different diffusion rates of free and bound palmitate across an unstirred fluid layer, nor attributable to nonequilibrium binding. Instead we argue that the most plausible explanation is accelerated dissociation of albumin-palmitate complexes mediated by the cell surface--an interpretation that also explains the uptake kinetics of other albumin-bound organic anions by perfused rat liver.

Adsorption↗
PubMed1986

Effects of L-leucine on palmitate metabolism and insulin release by isolated islets of fed and starved rats.

The occurrence of lipid metabolic changes associated with L-leucine (10 mM) stimulation of insulin release was investigated in isolated islets from either fed or starved rats. L-Leucine-stimulated secretion was potentiated by 3 mM glucose and/or 0.5 mM palmitate and was unaffected by 48 h of starvation. Islet palmitate oxidation showed a maximum rate at 3 mM glucose, and starvation increased it almost 2-fold. Regardless of the nutritional state, L-leucine strongly reduced the oxidation of palmitate and increased its incorporation into islet triacylglycerols and phospholipids at 3 mM glucose. This shift of fatty acid metabolism toward esterification might play a role in the mechanism of potentiation of the islet secretory response to L-leucine by glucose and palmitate.

Animals↗
PubMed1981

Palmitate and octanoate metabolism in bovine mammary tissue.

Effect of glucose on palmitate and octanoate metabolism was studied in bovine mammary tissue slices. Glucose stimulated palmitate esterification principally to form partial glycerides while decreasing palmitate oxidation. Glucose stimulated octanoate but not palmitate incorporation into triacylglycerols, suggesting that availability of intracellular medium-chain fatty acids may limit the final acylation reaction in triacylglycerol synthesis.

Animals↗
PubMed1985

Effects of feeding whole cottonseed to lactating dairy cows on glucose and palmitate metabolism.

Eight lactating Holstein dairy cows were fed corn silage-based diets with or without whole cottonseed at 18.5% of the dietary dry matter. At 42 days postpartum, a pulse injection of 100 mg glucose/kg body weight was given intravenously and plasma glucose concentration was monitored for 45 min. At 50 d postpartum, biopsies of adipose tissue and mammary tissue were taken and tissue slices were incubated in vitro with either uniform carbon-14 glucose or 1-carbon-14 palmitate. Basal concentration of plasma glucose was not affected by diet, although apparent distribution volume of glucose did seem to decrease due to feeding whole cottonseed. Feeding whole cottonseed decreased uptake of glucose and palmitate in both adipose tissue and mammary tissue and also decreased oxidation of glucose to carbon dioxide in both tissues. Palmitate oxidation was not affected by diet. Incorporation of carbon-14 from glucose into adipose tissue lipids was decreased in cows fed whole cottonseed. Results indicate that fat supplementation in the form of whole cottonseed may decrease palmitate incorporation and glucose utilization for glycerol and reducing equivalent synthesis in both adipose tissue and mammary tissue of lactating dairy cows.

Adipose Tissue↗
PubMed1976

The formation of heteroagglutinins in rats "chemically" splenectomized by ethyl palmitate, in comparison to animals surgically splenectomized.

In Wistar rats "chemically splenectomized" by an i.v. injection of ethyl palmitate the formation of heteroagglutinins against human O-erythrocytes has been followed. Ethyl palmitate applied 2 hrs before immunization induced on the 5th day a significant decrease of the antibody level. This temporary inhibition, however, was at a later stage replaced by a significant increase of antibody level with the peak of 8--14 days. Animals surgically splenectomized 24 hrs prior to immunization displayed a weak antibody response throughout the experiment. An injection of the ethyl palmitate on the 6th day after immunization induced a pronounced and persistent decrease of the antibody level. Surgical splenectomy performed within the same interval had a comparable effect. The experiments revealed that the inhibitory effect of ethyl palmitate on antibody production was temporary only, and at a later stage could be compensated by an enhanced antibody activity.

Agglutinins↗
PubMed1991

Acylation of cell-associated IL-1 by palmitic acid.

To determine whether membrane-associated IL-1 is palmitylated, we labeled LPS-activated human monocytes with [3H]palmitic acid. The plasma membranes were isolated, and the membrane proteins extracted and analyzed simultaneously by SDS-PAGE-autoradiography and Western blot analysis from the same gel. When the monocytes were labeled with [3H]palmitate, 23- and 31-kDa bands were visualized, for membrane-associated IL-1 and its precursor, respectively. The 31- and 23-kDa bands were excised from several gels and rehydrated and analyzed again by SDS-PAGE, autoradiography, and Western blot analysis. The 23- and 31-kDa bands appeared again by both methods. To further investigate membrane-associated IL-1 acylation, human monocytes were labeled with [3H]palmitate, the plasma membranes isolated, and the membrane proteins extracted by CHAPS detergent. Immunoprecipitation of isolated membrane proteins using anti-IL-1 antibodies revealed two bands of 23 and 31 kDa after autoradiography. The studies demonstrate that both membrane-associated IL-1 and the IL-1 precursor are acylated with palmitic acid.

Acylation↗
PubMed1989

Acylation of keratinocyte transglutaminase by palmitic and myristic acids in the membrane Anchorage region.

The membrane-bound form of keratinocyte transglutaminase was found to be labeled by addition of [3H] acetic, [3H]myristic, or [3H]palmitic acids to the culture medium of human epidermal cells. Acid methanolysis and high performance liquid chromatography analysis of palmitate-labeled transglutaminase yielded only methyl palmitate. In contrast, analysis of the myristate-labeled protein yielded approximately 40% methyl myristate and 60% methyl palmitate. Incorporation of neither label was significantly affected by cycloheximide inhibition of protein synthesis. The importance of the fatty acid moiety for membrane anchorage was demonstrated in three ways. First, the enzyme was solubilized from the particulate fraction of cell extracts by treatment with neutral 1 M hydroxylamine, which was sufficient to release the fatty acid label. Second, solubilization of active enzyme from the particulate fraction upon mild trypsin treatment resulted in a reduction in size by approximately 10 kDa and removal of the fatty acid radiolabels. Third, the small fraction of soluble transglutaminase in cell extracts was found almost completely to lack fatty acid labeling. Keratinocyte transglutaminase translated from poly(A+) RNA in a reticulocyte cell-free system was indistinguishable in size from the native enzyme, suggesting anchorage requires only minor post-translational processing. Thus, the data are highly compatible with membrane anchorage by means of fatty acid acylation within 10 kDa of the NH2 or COOH terminus.

Acetates↗
PubMed1989

[Effect of palmitate and phorbol ester on synthesis of phosphatidylcholine in isolated guinea pig gastric glands].

To better understand the mechanism of phosphatidylcholine synthesis in the stomach, [3H] choline incorporation into phosphatidylcholine in response to agents which have been shown to induce phosphatidylcholine biosynthesis in other tissues was examined using isolated guinea pig gastric glands. Palmitate and 12-O-tetradecanoyl phorbol 13-acetate (TPA) which has been shown to activate protein kinase C directly, stimulated [3H] choline incorporation into phosphatidylcholine in gastric glands, by 189 +/- 12.9%, and 129 +/- 10.4% of control, respectively (n = 4, p less than 0.01, p less than 0.05). On the other hand, dibutyryl cyclic AMP had no effect on the incorporation. When the glands were pulsed with [3H] choline followed by incubation in the presence of palmitate and TPA for 180 min to see the effects of the agents on the limiting step of the phosphatidylcholine synthesis, phosphatidyl-[3H] choline was increased to 167 +/- 7.5% and 142 +/- 7.5% of control respectively (n = 4, p less than 0.01, p less than 0.05). In parallel to the increase in phosphatidylcholine synthesis, phosphoryl-[3H] choline in the glands incubated with palmitate and TPA was decreased as compared with control. These results suggest that palmitate or TPA may stimulate phosphatidylcholine biosynthesis through the activation of cytidylyltransferase in the stomach.

Animals↗
PubMed1986

The HLA-D-associated invariant chain binds palmitic acid at the cysteine adjacent to the membrane segment.

The highly polymorphic HLA-D antigens are associated with a nonpolymorphic polypeptide chain, designated invariant chain. This invariant chain is shown to incorporate fatty acid. Invariant chain metabolically labeled with [3H]palmitic acid releases its label after treatment with hydroxylamine indicating an ester linkage of the palmitic acid. The binding of fatty acid to the invariant chain inhibits the formation of S-S-linked dimers. This suggests that the sole cysteine residue of the invariant chain is blocked by binding of fatty acid. A peptide shared by [3H]palmitic acid- or [35S]cysteine-labeled invariant chain digests supports the hypothesis that the palmitic acid binds to the cysteine which is located close to the membrane-spanning domain on the cytoplasmic site. Inhibition of N-glycosylation with tunicamycin demonstrates binding of the fatty acid to the nonglycosylated precursor of the invariant chain. Additionally, blocking of fatty acylation by cerulenin inhibits further maturation of the invariant chain, as sialylation.

Antibodies, Monoclonal↗
PubMed1986

Fatty acylation of cellular proteins. Temporal and subcellular differences between palmitate and myristate acylation.

Previous studies demonstrated that palmitate and myristate are covalently linked to distinct sets of cellular proteins and that the linkages through which these fatty acids are attached to the polypeptide chains are different (Olson, E. N., Towler, D. A., and Glaser, L. (1985) J. Biol. Chem. 260, 3784-3790). In the present study, the kinetics and subcellular sites of acylation of proteins with palmitate and myristate were examined in the BC3H1 muscle cell line. Acylation with myristate was an extremely early modification that appeared to take place cotranslationally or shortly thereafter for a variety of soluble and membrane-bound proteins. In contrast, acylation of proteins with palmitate was a post-translational event that occurred exclusively on membrane proteins. To begin to understand the intracellular pathways that acyl proteins follow during their maturation, the degree of glycosylation, and the nature of the interaction of these proteins with membranes were examined. The majority of acyl proteins were tightly associated with membranes and could not be removed by conditions that release peripheral proteins from membranes. However, only a minor fraction of acylated proteins were N-glycosylated. These data suggest that the acyltransferases that attach palmitate and myristate to proteins are present in different subcellular locations and demonstrate that these fatty acids are attached to newly synthesized acyl proteins at different times during their maturation. The lack of carbohydrate on the majority of integral membrane acyl proteins suggests that these proteins may follow intracellular pathways that are different from those followed by cell surface glycoproteins.

Acyltransferases↗
PubMed1979

Gas liquid chromatographic studies of [1-14C] palmitate uptake by the perfused guinea-pig heart.

In addition to the uptake of palmitate by the isolated perfused guinea-pig heart, there was a substantial release of longer chain fatty acids into the perfusate amounting to about 50% of the uptake of palmitate. Both the uptake of palmitate and the release of other fatty acids was diminished in the presence of 95% N2. The specific activity of myocardial palmitate was increased under 95% N2. No significant difference in the distribution of radioactivity between the different myocardial fatty acids occurred between 95% O2 and 95% N2.

Animals↗
PubMed1983

Experimental elimination of the splenic function by ethyl and methyl palmitate and significance of these substances from an immunological point of view.

Our experiments with rats dealt with finding a possible functional splenic elimination by using an i.v. injection of ethyl and methyl palmitate emulsion. Simultaneously, immunological effects were determined in both substances. After applying ethyl palmitate an extensive splenic necrosis could be induced resulting in an elimination of the sequestrational splenic function to an extent comparable to surgical splenectomy. Histological examinations of liver, lungs, kidneys, heart, bone marrow, lymph nodes and thymus together with the follow-up of some metabolic indicators in the spleen and liver (determination of proteins, DNA, RNA, EFA, transaminases in blood serum and observations of proteosynthesis) showed that the effect of ethyl palmitate on the spleen is selective and that there is no marked damage of other organs. Methyl palmitate is important for its inhibition of antibody response manifesting itself in a reduced production of heteroagglutinins and in a prolonged survival time of skin semiallografts.

Animals↗
PubMedDate not supplied

[Utilization of 1-14C- glucose, 1-14C-acetate and 1-14C-palmitate during lipid synthesis in vitro in the liver and skeletal muscles of pigs at different ontogenic stages].

The specific radioactivity of lipids synthesized in the liver and quadriceps muscle of 110-day embryos, and 1-, 30-, 60-, 90-day and 12-month pigs in vitro from [1-14C]acetate, [1-14C] glucose and [1-14C] palmitate was investigated. The lipid synthesis from most of the above compounds in the fetal liver developed at a greater rate and in the fetal skeletal muscles at a smaller rate than in livers and skeletal muscles of newborn piglets. During the first months after birth the lipid synthesis from [1-14C] acetate, [1-14C] glucose and [1-14C] palmitate in the liver increased gradually. At the same time the lipid synthesis in skeletal muscles from [1-14C]glucose and [1-14C]palmitate decreased and from [1-14C] acetate increased. The utilization of the above compounds in the lipid synthesis of the liver and quadriceps muscle of pigs follows the decreasing order: [1-14C] palmitate greater than [1-14C]acetate greater than [1-14C]glucose.

Acetates↗
PubMed1977

The inhibitory effect of methyl palmitate on heteroagglutinin formation in rats.

In Wistar rats the immunosuppressive effect of methyl palmitate on the formation of heteroagglutinins against human O-group erythrocytes was followed. An i.v. injection of methyl palmitate both delayed the heteroagglutinin formation and decreased its intensity. The inhibitory effect of methyl palmitate was not accompained by the subsequent hyperactive phase as could be observed in the previous experiments using ethyl palmitate.

ABO Blood-Group System↗
PubMed1995

[A study on the effect of cortisol and progesterone on cytosolic arachidonic and palmitic acid concentrations in cultured human myometrial cells].

Glucocorticoids inhibit prostaglandin synthesis in several cell types, presumably by inhibiting arachidonic acid deacylation from phospholipids. We studied the effects of cortisol (F) and progesterone (P) on fatty acid release from cultured human myometrial cells. Confluent monolayer cultures of myometrial cells were adapted to steroids containing medium for 24 hours and the intracellular arachidonic acid and palmitic acid concentrations were determined. In the presence of fetal calf serum (FCS), the palmitic acid concentrations significantly decreased after the addition of 10(-7)M F. In the absence of FCS, the concentrations of both fatty acids were markedly increased after the addition of F. During oxytocin stimulation, the arachidonic acid concentration did not change but the palmitic acid concentration decreased slightly after the addition of F. A similar evaluation was done with P. The palmitic acid concentration decreased slightly after the addition of 10(-5)M P in the presence of FCS but increased markedly in the absence of FCS. During stimulation with oxytocin, the fatty concentrations of fatty acids decreased significantly in a dose-dependent manner. These results suggest that both F and P are implicated as regulatory factors in the activation of arachidonic acid cascade.

Arachidonic Acid↗