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PubMed1975

The effect of essential fatty acid deficiency upon fatty acid uptake by the brain.

Young adult rats, either control or essential fatty acid deficient, were administered either [3-H] oleic acid or [3-H] arachidonic acid by stomach tube. In addition, a group of control rats was given [3-H] palmitic acid. The rats were killed at various times therafter, and the radioactivity of the lipids of brain and plasma was examined. In confirmation of previous work, the blood lipid label was found to rise rapidly and then fall, wheras the activity of brain lipids increased slowly and did not show a decline through the 24-h period studied. Analysis of the brain uptake data according to first-order kinetics confirmed the impressions gained from visual inspection of the data. The initial rate of uptake of arachidonic acid was about 4.5 times that of oleic acid in control animals and in deficient animals. Essential fatty acid deficiency, however, did not induce an altered rate of uptake for either oleic acid or arachidonic acid. The rate of uptake of palmitic acid by control rats was not significantly different from that of oleic acid. Even though the initial rates of incorporation of oleic and arachidonic acids were not changed during essential fatty acid deficiency, the final levels of radioactivity obtained in brain lipids were higher in deficient rats with both fatty acids. The plateau value obtained with oleic acid was 1.5 times higher in deficient animals, while the plateau value for arachidonic acid was 1.7 times higher. An experiment in which deficient animals were allowed access to a control diet for 12 or 24 h prior to the labeling experiment suggested that the higher levels of radioactivity found in brain lipids of deficient animals was not due to an isotope dilution effect. Such animals still displayed the labeling pattern of deficient animals with arachidonic acid, while the results with oleic acid varied somewhat. Our results suggest that essential fatty acid deficiency does not alter the ability of the brain to take up the fatty acids studied. However, the fatty acids, especially arachidonic, are retained in the brain to a greater extent in the deficient animals.

Animals↗
PubMed1998

Measles virus fusion protein is palmitoylated on transmembrane-intracytoplasmic cysteine residues which participate in cell fusion.

[3H]palmitic acid was metabolically incorporated into the viral fusion protein (F) of Edmonston or freshly isolated measles virus (MV) during infection of human lymphoid or Vero cells. The uncleaved precursor F0 and the F1 subunit from infected cells and extracellular virus were both labeled, indicating that palmitoylation can take place prior to F0 cleavage and that palmitoylated F protein was incorporated into virus particles. [3H]palmitic acid was released from F protein upon hydroxylamine or dithiothreitol treatment, indicating a thioester linkage. In cells transfected with the cloned MV F gene, in which the cysteines located in the intracytoplasmic and transmembrane domains (Cys 506, 518, 519, 520, and 524) were replaced by serine, a major reduction of [3H]palmitic acid incorporation was observed for F mutated at Cys 506 and, to a lesser extent, at Cys 518 and Cys 524. We also observed incorporation of [3H]palmitic acid in the F1 subunit of canine distemper virus F protein. Cell fusion induced by cotransfection of cells with MV F and H (hemagglutinin) genes was significantly reduced after replacement of Cys 506 or Cys 519 with serine in the MV F gene. Transfection with the F gene with a mutation for Cys 518 abolished cell fusion, although less mutant protein was detected on the cell surface. These results suggest that the F protein transmembrane domain cysteines 506 and 518 participate in structures involved in cell fusion, possibly mediated by palmitoylation.

Acylation↗
PubMed2006

Acylation of CD44 and its association with lipid rafts are required for receptor and hyaluronan endocytosis.

CD44 is a cell surface receptor for the extracellular matrix macromolecule hyaluronan. In addition, CD44 mediates the endocytosis of hyaluronan leading to its subsequent degradation within lysosomes. Using model systems of COS-7 and Flp-293 cells, we demonstrate that the association of CD44 with lipid rafts is essential for the endocytosis of hyaluronan but not the extracellular binding. Further, we demonstrate that palmitoylation of CD44 on two highly conserved cysteine residues is essential for the association with lipid rafts as determined by density gradient ultracentrifugation. Mutations of either cysteine residues or pretreatment of cells with the palmitic acid analog 2-bromopalmitate, reduced the [3H]palmitic acid incorporation into CD44 and prevented CD44-lipid rafts association. Preventing CD44 palmitoylation had no effect on the binding of hyaluronan but inhibited hyaluronan internalization. The turnover of the CD44 receptor itself was also affected by blocking its association with lipid rafts. Using cycloheximide to prevent de novo protein synthesis, palmitoylation-deficient cysteine mutants underwent slower turnover from cell surface compared with the palmitoylation-intact wild type, as determined by immunofluorescence and Western blotting. These results indicate that palmitoylation of CD44 is a critical driving determinant to CD44 association with lipid rafts and, concomitantly, the rates of hyaluronan endocytosis and CD44 turnover from cell surface.

Acylation↗
PubMed1978

Is the fat breath test effective in the diagnosis of fat malabsorption and pancreatic disease?

An attempt was made to evaluate the diagnostic effectiveness of the 14CO2-tripalmitin breath test in the screening or diagnosis of fat malabsorption. The differential absorption of 14C-tripalmitin and palmitic acid was evaluated in the diagnosis of pancreatic insufficiency. 24 controls, 13 patients with steatorrhea and 6 with pancreatic disease (4 of them with sufficiency) were studied. 81 breath tests were performed using 75 ml sour cream as a carrier. In 11 cases the 14C-tripalmitin test was repeated using 27 g corn oil as carrier. Both the 14C-tripalmitin and 14C-palmitic acid breath tests failed to provide any discrimination between normals and patients with fat malabsorption. Variation in type and amount of the carrier fat did not alter these results. 14C-tripalmitin absorption was distinctly abnormal in the patients with pancreatic insufficiency. The differential absorption of 14C-tripalmitin and 14C-palmitic acid provided an even better separation between patients with and without pancreatic disease. In contrast to some other investigators we did not find the 14C-tripalmitin and/or palmitic acid breath tests useful in the diagnosis or screening of fat malabsorption. These tests appear promising in the diagnosis of pancreatic disease.

Adolescent↗
PubMed1995

Metabolism of cottonseed microsomal N-acylphosphatidylethanolamine.

N-acylphosphatidylethanolamine (NAPE) was recently shown to be synthesized in vitro in cottonseed microsomes by the direct N-acylation of phosphatidylethanolamine (PE) with unesterfied fatty acids (K.D. Chapman and T. S. Moore, 1993, Plant Physiol. 102, 761-769). Here we examine the relationship of the synthesis and turnover of NAPE in cottonseed microsomes to the O-acylation of other membrane phospholipids. PE was N-acylated in a time-dependent manner with [1-14C]palmitic acid independent of exogenously supplied ATP. O-Acylation of PE and phosphatidylcholine (PC) with [1-14C]palmitic acid proceeded only in the presence of ATP. Further radiolabeling experiments with [1-14C]palmitoylCoA and phosphatidyl(N-[1-14C]-palmitoyl)ethanolamine indicated that O-acylation of phospholipids occurred via an acylCoA intermediate and not via an NAPE intermediate. [1-14C]palmitic acid was released from PC[1-14C-dipalmitoyl] in cottonseed microsomes in a Ca(2+)-dependent manner and this [14C]-FFA was incorporated into [14C]NAPE in a linear fashion. Cottonseed NAPE was selectively hydrolyzed to N-acylethanolamine (NAE) and N-acyl lysophosphatidylethanolamine (NAlysoPE) by Ca(2+)-independent, membrane-bound phospholipase D and A activities, respectively. NAlysoPE was not hydrolyzed to NAE, indicating that the phospholipase D that was active toward NAPE did not recognize NAlysoPE; instead NAlysoPE was converted to NAPE in the presence of Ca2+. Collectively, our results indicate that NAPE synthesis and the O-acylation of other phospholipids occur by two separate pathways and that microsomal NAPE is selectively turned over by membrane-bound phospholipase activities. A pathway for the metabolism of cottonseed NAPE is outlined.

Acylation↗
PubMed1989

Agonist-enhanced palmitoylation of platelet proteins.

When washed human platelets were incubated with [3H]palmitic acid, radioactivity was incorporated into a major 38 kDa doublet and several minor proteins that were resolved on polyacrylamide gels. The radioactivity associated with the proteins remained after extractions with organic solvents, but it was lost after hydroxylamine treatment or mild alkali methanolysis. The products of these reactions were analyzed by thin-layer chromatography and HPLC. They were identified as palmitohydroxamate and methyl palmitate, respectively, indicating that the palmitic acid was covalently linked to the proteins via oxygenester or thioester bonds. In resting platelets, radioactivity was detected in the 38 kDa proteins 2 min after the addition of [3H]palmitic acid. A plateau was reached between 5 and 11 min, at which time radioactivity was also detected in a 23 kDa protein. Thrombin elicited faster and greater incorporation of label into both proteins. Phorbol 12-myristate 13-acetate (PMA) led to a similar, but slower increase of radioactivity in the 38 kDa proteins, while collagen and A23187 were less effective. Enhanced palmitoylation may be closely linked to platelet activation, as suggested by the following observations: (1) in thrombin- or PMA-activated platelets, the time-course of aggregation correlated with the time-course of enhanced palmitoylation of the 38 kDa proteins; (2) in platelets activated by various concentrations of thrombin with or without prostacyclin, aggregation was correlated with the enhanced incorporation of radioactivity into the 38 kDa proteins.

Blood Platelets↗
PubMed1996

Phytanic acid activation in rat liver peroxisomes is catalyzed by long-chain acyl-CoA synthetase.

In Refsum disease, disorders of peroxisome biogenesis, and rhizomelic chondrodysplasia punctata, pathological accumulation of phytanic acid results from impaired alpha-oxidation of this branched-chain fatty acid. Previous studies from this laboratory indicated that activation of phytanic acid to its CoA derivative precedes its alpha-oxidation in peroxisomes. It was reported that this reaction is catalyzed by a unique phytanoyl-CoA synthetase in human peroxisomes. We wanted to determine whether phytanic acid activation in rats required long-chain acyl-CoA synthetase (LCS), very long-chain acyl-CoA synthetase (VLCS), or a different enzyme. To test directly whether LCS could activate phytanic acid, rat liver cDNA encoding this enzyme was transcribed and translated in vitro. The expressed enzyme had both LCS activity (assayed with palmitic acid, C16: 0) and phytanoyl-CoA synthetase activity; VLCS activity (assayed with lignoceric acid, C24: 0) was not detectable. The ratio of phytanoyl-CoA synthetized activity to palmitoyl-CoA synthetase activity for LCS synthetized in vitro (approximately 205) was higher than that observed in peroxisomes isolated from rat liver (5-10%), suggesting that the expressed enzyme contained sufficient phytanoyl-Coa synthetase activity to account for all activity observed in intact peroxisomes. Further experiments were carried out to verify that phytanic acid was activated by LCS in rat liver peroxisomes. Attempts to separate LCS from phytanoyl-CoA synthetase by chromatography on several matrices were unsuccessful. Preparative isoelectric focusing revealed that phytanoyl-CoA synthetase and LCS had indistinguishable isoelectric points. Phytanoyl-CoA synthetase activity was inhibited by unlabeled palmitic acid but not by lignoceric acid. Heat treatment inactivated both phytanoyl-CoA and palmitoyl-CoA synthetase activities at similar rates. 5,8,11,14-Eicosatetraynoic acid inhibited activation of phytanic acid and palmitic acid in a parallel dose-dependent manner, whereas activation of lignoceric acid was not affected. These data support our conclusion that rat liver LCS, an enzyme known to be present in peroxisomal membranes, has phytanoyl-CoA synthetase activity.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1982

Role of an acidic compartment in synthesis of disaturated phosphatidylcholine by rat granular pneumocytes.

A possible role for an acidic subcellular compartment in biosynthesis of lung surfactant phospholipids was evaluated with granular pneumocytes in primary culture. Incubation with chloroquine (100mum) was used to perturb this compartment. With control cells, incorporation of [9,10-(3)H]palmitic acid into total lipids and into total phosphatidylcholines increased linearly with time up to 4h. Total incorporation into phosphatidylcholine during a 1h incubation was 999+85pmol of [9,10-(3)H]palmitic acid, 458+/-18pmol of [1-(14)C]oleic acid and 252+/-15pmol of [U-(14)C]glucose per mug of phosphatidylcholine phosphorus. The cellular content of either disaturated phosphatidylcholine or total phosphatidylcholines did not change during a 2h incubation with chloroquine. In the presence of chloroquine, the specific radioactivity of [(3)H]palmitic acid in disaturated phosphatidylcholine increased by 40%, and that of disaturated-phosphatidylcholine fatty acids from [U-(14)C]glucose increased by 125%. Incorporation of [1-(14)C]oleic acid into phosphatidylcholine was decreased by chloroquine by 79% and 33% in the presence or absence of palmitic acid respectively. Chloroquine stimulated phospholipase activity in intact cells, and in sonicated cells at pH4.0, but not at pH8.5. The observations indicate that chloroquine stimulates synthesis of disaturated phosphatidylcholine in granular pneumocytes from fatty acids, both exogenous and synthesized de novo, which can be due to stimulation of acidic phospholipase. This stimulation of acidic phospholipase A activity by chloroquine appears to be coupled to the synthesis of disaturated phosphatidylcholine, thereby enhancing remodelling of phosphatidylcholine synthesized de novo. Our findings, therefore, implicate the involvement of an acidic subcellular compartment in the remodelling pathway of disaturated phosphatidylcholine synthesis by granular pneumocytes.

Animals↗
PubMed1997

Mechanism of cAMP-induced Ca2+ influx in Dictyostelium: role of phospholipase A2.

cAMP-induced Ca2+ influx in Dictyostelium follows two pathways: a G-protein-dependent pathway where influx is reduced by 50-70% in Galpha2 and Gbeta-negative strains and a heterotrimeric G-protein-independent pathway. Using a pharmacological approach, we found that phospholipase A2 (PLA2) is the target of both pathways. The products of PLA2 activity, arachidonic acid (AA) and palmitic acid, induced Ca2+ influx to a similar extent as cAMP. Half-maximal activation occurred at 3 microM AA and saturation at 10 microM AA. The response to AA was quantitatively similar throughout early differentiation and thus independent of cAMP-receptor concentration. Synergy experiments revealed that cAMP and AA acted through identical pathways. The PLA2-activating peptide, a peptide with sequence similarity to the G-protein beta-subunit, activated Ca2+ influx. The G-protein-independent pathway was sensitive to genistein but not to blockers of protein kinase C and other kinases, suggesting that tyrosine kinase may directly or indirectly activate PLA2 in this case.

Animals↗
PubMed1986

Analysis of chinoform binding to human serum albumin by an improved partition equilibrium method.

Previous methods such as equilibrium dialysis to measure chinoform binding to human serum albumin are flawed with problems due to the drug's poor solubility in neutral aqueous solutions and its strong adsorption onto the surfaces of dialysis membrane and other apparatus. Accordingly, we adopted a previously reported improved partition equilibrium method to keep off such difficulties, and developed additionally a rapid method using oil-wells. Both of these methods were used in this study. The equilibration of both partition and binding was attained after 6 h by the standard method and after 2 h by the rapid method. Two binding sites were found on the albumin molecule. One had an extremely large affinity constant of 10(8) M-1 and the other had a moderate one of 10(6) M-1. These values obtained with both methods agreed well and were sufficiently reproducible. The bound percentage of chinoform in serum was estimated at 99.999% under the condition where chinoform reveals its nervous toxicity. The binding constant had a maximum at pH 7.6, the physiological pH of serum. The pH profile suggested the participation of a histidine residue in the binding site. The inhibition experiment with palmitic acid revealed that the first binding site of chinoform was not identical with that of palmitic acid. The present method is applicable to analyses of protein binding by other drugs showing similar physicochemical properties as chinoform.

Clioquinol↗
PubMed1994

Hydration and localization of diacylglycerol in the insect lipoprotein lipophorin. A 13C-NMR study.

In order to probe the organization of diacylglycerol (DG) in lipophorin, 13C-enriched lipophorin was prepared for NMR investigations. We obtained 13C-enriched lipophorin labeled exclusively in DG by feeding insects tobacco leaves coated with [1-13C]palmitic acid or [1-13C]oleic acid. Lipophorins enriched up to 5% with a [13C]fatty acid were obtained by this procedure. NMR studies of the isolated lipophorin DG showed that palmitic acid accumulates almost entirely (> 90%) in the sn-1 position. Oleic acid was found equally distributed between the sn-1 and sn-2 positions, yielding a DG enriched equally at both positions. The 13C-NMR spectra of both [13C]palmitate- and [13C]oleate-enriched lipophorins showed that DG had one narrow carbonyl resonance indicative of rapid motion. A comparative analysis of the 13C carbonyl chemical shift data for DG in organic solvents, aqueous solutions, and dispersions with the DG carbonyl chemical shift of native lipophorin enriched in [13C]palmitate or [13C]oleate shows a high degree of water exclusion from the DG carbonyls in lipophorin. This result is consistent with the existence of a lipophorin lipid core containing most of the lipophorin DG. This study represents the first attempt to elucidate the organization of DG in lipophorin. The possibility of obtaining [13C]DG-enriched lipophorins, selectively enriched in one or both acyl chains of DG, should provide a powerful tool for further analysis of the organization and the dynamic properties of DG in native lipoproteins.

Animals↗
PubMed2002

Expression of fatty acid binding proteins inhibits lipid accumulation and alters toxicity in L cell fibroblasts.

High levels of saturated, branched-chain fatty acids are deleterious to cells and animals, resulting in lipid accumulation and cytotoxicity. Although fatty acid binding proteins (FABPs) are thought to be protective, this hypothesis has not previously been examined. Phytanic acid (branched chain, 16-carbon backbone) induced lipid accumulation in L cell fibroblasts similar to that observed with palmitic acid (unbranched, C(16)): triacylglycerol >> free fatty acid > cholesterol > cholesteryl ester >> phospholipid. Although expression of sterol carrier protein (SCP)-2, SCP-x, or liver FABP (L-FABP) in transfected L cells reduced [(3)H]phytanic acid uptake (57-87%) and lipid accumulation (21-27%), nevertheless [(3)H]phytanic acid oxidation was inhibited (74-100%) and phytanic acid toxicity was enhanced in the order L-FABP >> SCP-x > SCP-2. These effects differed markedly from those of [(3)H]palmitic acid, whose uptake, oxidation, and induction of lipid accumulation were not reduced by L-FABP, SCP-2, or SCP-x expression. Furthermore, these proteins did not enhance the cytotoxicity of palmitic acid. In summary, intracellular FABPs reduce lipid accumulation induced by high levels of branched-chain but not straight-chain saturated fatty acids. These beneficial effects were offset by inhibition of branched-chain fatty acid oxidation that correlated with the enhanced toxicity of high levels of branched-chain fatty acid.

Acetyl-CoA C-Acetyltransferase↗
PubMed1999

Dynamic Interfacial Tension of Surfactant Mixtures at Liquid-Liquid Interfaces.

Dynamic interfacial tensions for surfactant mixtures at liquid-liquid interfaces were obtained with a drop volume tensiometer. The surfactants tested were Triton X-100, palmitic acid, and Span 80 at both the water-hexadecane and water-mineral oil interfaces. Two-surfactant mixtures were examined with the surfactants initially dissolved in different phases to minimize bulk-phase interactions. For concentrations below the CMC, it was found that the adsorption kinetics of palmitic acid and Triton X-100 mixtures were dominated by the latter surfactant. Apparent diffusion coefficients were obtained for Triton X-100 both in the absence and in the presence of palmitic acid. These values were largely insensitive to the presence of palmitic acid. For mixtures of Span 80 and Triton X-100, the adsorption kinetics were found to be influenced significantly by both surfactants. In this case, relative changes in surfactant concentrations affected the dynamic interfacial tension of the mixed system. A previously proposed multicomponent adsorption model described the dynamic interfacial tension adequately at low concentrations of Triton X-100, when desorption could be neglected. At higher concentrations, modifications were needed to account for solubilization into the oil phase. These corrections allowed the model to describe the long time adsorption quite well. However, predicted values of short time interfacial tensions were overestimated, likely due to a synergistic interaction of the two surfactants. Copyright 1999 Academic Press.

Journal Article↗
PubMed1990

Effects of dietary cholesterol and fatty acids on plasma cholesterol level and hepatic lipoprotein metabolism.

The effects of dietary cholesterol and fatty acids on the plasma cholesterol level and rates of very low density lipoprotein (VLDL) cholesterol secretion and low density lipoprotein (LDL) transport through LDL receptors in the liver of the hamster were investigated. Increases of plasma VLDL- and LDL-cholesterol levels and VLDL-cholesterol secretion from hepatocytes were observed in animals fed a diet enriched with 0.1% cholesterol for 2 weeks in comparison with animals fed a control diet. The addition of dietary palmitic acid accelerated the effect of dietary cholesterol on plasma VLDL- and LDL-cholesterol levels and VLDL-cholesterol secretion from hepatocytes. Dietary linoleic acid accelerated the effect of dietary cholesterol on VLDL-cholesterol secretion from hepatocytes and diminished the effect on the plasma LDL-cholesterol level. Hepatic LDL receptor activity was considerably suppressed by a control diet containing 0.05% cholesterol and a further small suppression was induced by a diet enriched with 0.1% cholesterol with or without 5% palmitic acid. However, dietary linoleic acid diminished the effect of dietary cholesterol on the suppression of hepatic LDL receptor activity. These results suggest that dietary palmitic acid augments the effect of dietary cholesterol in elevating the plasma LDL-cholesterol level through acceleration of VLDL-cholesterol secretion from the liver, and that dietary linoleic acid diminishes the effect of dietary cholesterol in elevating the plasma LDL-cholesterol level by preventing the suppression of hepatic LDL receptor activity induced by cholesterol.

Animals↗
PubMed1992

Identification of palmitoylation sites on CD4, the human immunodeficiency virus receptor.

We report that the cell surface glycoprotein CD4 expressed in HeLa cells can be metabolically labeled with [3H]palmitic acid. Analysis of the 3H-label after hydrolysis of the protein indicated that it was incorporated predominantly as palmitic acid. Comparison of the amount of [3H]palmitate incorporated into CD4 with that incorporated into a protein known to contain one molecule of esterified palmitate suggested that one to two molecules of palmitate were added to CD4. The fatty acid was readily cleaved from CD4 by treatment with weak base suggesting a thioester linkage. Mutations of each of 2 cysteine residues, Cys394 and Cys397, in CD4 at the junction of the transmembrane and cytoplasmic domains reduced labeling with [3H]palmitic acid, and mutation of both cysteines eliminated labeling. These results indicate that both cysteines are esterified to palmitate. Modification with palmitate was not required for expression of CD4 on the cell surface or for binding of p56lck to its cytoplasmic domain.

Amino Acid Sequence↗
PubMed1991

Noradrenaline stimulates glucose transport in rat brown adipocytes by activating thermogenesis. Evidence that fatty acid activation of mitochondrial respiration enhances glucose transport.

The mechanisms by which noradrenaline, lipolytic agents and long-chain fatty acids stimulate glucose transport were investigated in rat brown adipocytes. Glucose transport was evaluated with tracer D-[U-14C]glucose and cell respiration was measured polarographically. Noradrenaline increased basal oxygen consumption (8-10-fold) and glucose transport (4-5-fold) in a dose-dependent manner, with a maximal stimulation at 100 nM. The stimulatory effects of noradrenaline on respiration and glucose transport were selectively mimicked by dibutyryl cyclic AMP (DBcAMP), 3-isobutyl-1-methylxanthine, cholera toxin and physiological concentrations of palmitic acid. Cytochalasin B completely blocked the effects of these agents on glucose transport. The beta-adrenergic antagonist propranolol inhibited noradrenaline-induced glucose transport, but did not affect the action of DBcAMP, palmitic acid or cholera toxin on this process. The specific inhibitor of mitochondrial carnitine palmitoyltransferase, 2-tetradecylglycidic acid (McN 3802) (50 microM), inhibited the stimulatory effects of noradrenaline (100 nM) and palmitic acid (0.5 mM) on both glucose transport and mitochondrial respiration. Significantly, McN 3802 failed to affect insulin (1 nM) action under identical experimental conditions. These results demonstrate that (a) the stimulatory effects of noradrenaline on brown-adipocyte respiration and glucose transport can be dissociated from those induced by insulin, and (b) noradrenaline increases glucose transport indirectly, by activating adenylate cyclase via beta-adrenergic pathways and by stimulating mitochondrial oxidation of fatty acids.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Free fatty acids in gallstones in mice fed a diet containing cholic acid.

In mice, combined addition of 1% cholesterol and 0.5% cholic acid to a diet induced cholesterol gallstones within 40 days as a result of the supersaturation of cholesterol in the bile, as has been reported. The major component of the gallstone was cholesterol, which was measured by HPLC. In this study, however, single addition of 1% cholic acid to a diet, which did not decrease cholesterol solubilizing capacity in bile, contributed to gallstone formation in mice within 50 days. The gallstones thus formed contained a large amount of palmitic acid. In the hepatic bile of this animal, palmitic acid was also detected; however, no solid material was observed by light and polarized-light microscopes. Free fatty acids such as palmitic acid seem to be dissolved in a complex micelle composed of bile acids and lecithin. This probably causes gallstone formation by reducing cholesterol solubilizing capacity in bile.

Animals↗