Showing papers on "Fatty acid-binding protein published in 1991"
TL;DR: It is concluded that fatty acids or fatty acid metabolites activate the aP2 gene and subsequently modulate its expression and the role of fatty acids in the regulation of adipose-related genes is investigated.
243 citations
TL;DR: The complete nucleotide sequence encoding a Schistosoma mansoni protein termed Sm14 was determined from cDNA clones propagated in bacteriophage lambda gt11 in Escherichia coli and Immunofluorescence experiments show that tubercles, which are structures located on the dorsal surface of adult male schistosome and known to contain lipids, are stained using antibodies raised to the beta-galactosidase fusion protein.
163 citations
TL;DR: Several digestion and absorption specific steps are worth studying with reference to the crucial role of polyunsaturated fatty acids in the organism, and for example adaptation of possible dietary supplements.
Abstract: Polyunsaturated fatty acids play an important part in the structure and function of cellular membranes and are precursors of lipid mediators which play a key role in cardiovascular and inflammatory diseases. Dietary sources of essential fatty acids are vegetable oils for either linoleic or alpha-linolenic acids, and sea fish oils for eicosapentaenoic and docosahexaenoic acids. Because of the specificity of the pancreatic lipid hydrolases, triglyceride fatty acid distribution is an essential parameter in the digestibility of fats. The efficiency of the intestinal uptake depends on the hydrolysis and especially on their micellarization. n-3 polyunsaturated fatty acid ethyl ester digestion is recognized to be impaired, but n-3 polyunsaturated fatty acid triglyceride hydrolysis remains a controversial point, and to some authors explains differences observed between vegetable and fish oil absorption. So additional studies are required to investigate this intestinal step. In enterocytes, morphological and biochemical absorption processes involve reesterification of long-chain fatty acids and lipoprotein formation. At this level, specific affinity of I- and L-FABPc (cytosolic fatty acid binding proteins) to polyunsaturated fatty acids requires further investigation. A better understanding of the role of these FABPc might bring to light the esterification step, particularly the integration of polyunsaturated fatty acids into phospholipids. With reference to differences published between fish and vegetable oil absorption, longer-term absorption studies appear essential to some authors. Polyunsaturated fatty acid absorption is thought to be not very dissimilar to that of long-chain mono-unsaturated fatty acid absorption. However, several digestion and absorption specific steps are worth studying with reference to the crucial role of polyunsaturated fatty acids in the organism, and for example adaptation of possible dietary supplements.
127 citations
TL;DR: The lack of fluorescence self-quenching upon binding 2 mol of either trans- or cis-parinaric acid/mol L-FABP is consistent with the presence of two binding sites with dissimilar orientation in the L- FABP, which predicts a structurally different binding site or sites.
114 citations
TL;DR: The stratum corneum contains a complex mixture of polar and nonpolar lipids in its intercellular spaces that have been investigated for their role in providing the epidermal barrier to transcutaneous water loss, the selective barrier from the inside to the outside of the organism and partly the process of physiological desquamation.
Abstract: The stratum corneum contains a complex mixture of polar and nonpolar lipids in its intercellular spaces. These lipids, present in form of multiple lamellae, have been investigated for their role in providing the epidermal barrier to transcutaneous water loss, the selective barrier from the inside to the outside of the organism and partly the process of physiological desquamation. The composition of these lipids varies from species to species, with the body region and the degree of keratinocyte differentiation. The most undifferentiated layers of the epidermis contain typical membrane lipids, phospholipids, while more differentiated layers contain ceramides, cholesterol and free fatty acids. Essential fatty acids are essential for the maintenance of the lamellar structures and epidermal barrier function. Epidermal linoleic and arachidonic acids derive from exogenous sources. Only recently attempts have been made to elucidate the timing and regulation of epidermal fatty acid metabolism. Keratinocytes do not express a low molecular weight fatty acid binding protein like other cells active in lipid metabolism, but may employ alternative ways in fatty acid uptake and metabolism.
99 citations
TL;DR: The results indicate the usefulness of the photoreactive fatty acid in identifying cellular fatty acid binding proteins, and its potential to elucidate the spatial and temporal distribution of fatty acids in intact cells.
98 citations
TL;DR: The process of activation by fatty acids, rather than the expression of the aP2 gene, is unique to adipose cells, and activation of both genes appears not to be mediated by the CCAAT enhancer binding protein, a nuclear factor reported as transactivator of theAP2 promoter activity.
79 citations
TL;DR: A minor absorption into blood of long‐chain fatty acids compared to the medium‐ Chain fatty acids is confirmed and differences in the catabolism of the fatty acids according to their chain length and their degree of unsaturation are highlighted.
Abstract: Simultaneous portal blood absorption and intestinal mucosal catabolism of labelled fatty acids were investigated. Anaesthetized adult Wistar rats were infused intraduodenally either with 90 mumol of capric (C10:0), oleic (C18:1), linoleic (C18:2) or arachidonic (C20:4) 1–14C acids or with 30 mumol of each labelled fatty acid in addition to 30 mumol of oleic acid and 30 mumol of monopalmitin. For mixed infusates, experiments were carried out with two additional long-chain fatty acids: palmitic (C16:0) and erucic (C22:1) 1–14C acids. Radioactivity was quantified in the lipids and in the catabolic products in portal blood recovered at 5 min intervals for 1 h after infusion. At the end of the experiment, the disappearance of radioactivity from the mucosa was quantified. When labelled fatty acids were infused alone, 49% of the radiolabelled lipid disappearing from the mucosa was recovered in the blood for C10:0, but only 7.8% for C18:1, 6.4% for C18:2 and 10.6% for C20:4. With mixed infusates, 41% of the radiolabelled lipid disappearing from the mucosa was recovered in the blood for C10:0 compared with 12% for C18:1, 10.2% for C18:2, 10.5% for C20:4 and 2.7% for C16:0 and 2% for C22:1. Labelled catabolites appear with the same profiles as those of the respective fatty acids in blood. These studies confirm a minor absorption into blood of long-chain fatty acids compared to the medium-chain fatty acids and highlight differences in the catabolism of the fatty acids according to their chain length and their degree of unsaturation. The differences might be related to the differences in the fatty acid hydrosolubility and to their different affinities for the I- and L-cytosolic fatty acid binding proteins. These phenomena may be important in nutrition in relation to the availability of essential fatty acids.
63 citations
TL;DR: Data indicate that the reduction in the level of fatty acid synthase mRNA is a factor in the pSt-mediated suppression of fatty Acid synthase synthesis in porcine adipose tissue.
Abstract: A cDNA for porcine fatty acid synthase was isolated and used to examine the tissue distribution of fatty acid synthase mRNA within the pig and to determine the impact of recombinant porcine somatotropin (rpSt) and the level of dietary protein on fatty acid synthase mRNA abundance in pig liver and adipose tissue. A 1.5-kb cDNA representing the thioesterase domain of porcine fatty acid synthase was isolated from a lambda gt 11 liver cDNA library. Northern analysis with total RNA extracted from adipose tissue, liver, heart, lung, kidney and intestine revealed a single major fatty acid synthase mRNA species of 8-9 kb. The amount of fatty acid synthase mRNA in hepatic tissue was 25% of the amount in adipose tissue, which suggests that the liver may be a significant site of fatty acid synthesis in the pig. Fatty acid synthase mRNA abundance was significantly reduced in the adipose tissue (P less than 0.01) and the liver (P less than 0.1) by chronic daily administration (60 micrograms/kg) of rpSt. In addition, increasing the amount of dietary protein decreased (P less than 0.1) the abundance of fatty acid synthase mRNA in adipose tissue but had no effect on liver fatty acid synthase expression. In contrast, the abundance of adipose fatty acid binding protein mRNA was unaffected by rpSt or dietary protein. These data indicate that the reduction in the level of fatty acid synthase mRNA is a factor in the pSt-mediated suppression of fatty acid synthesis in porcine adipose tissue.
60 citations
TL;DR: Results are consistent with a close proximity of bound fatty acids to the tyrosine and tryptophan residues and with immobilization of the polyene fatty acids in the fatty acid-binding site(s) of L-FABP and I-F ABP.
59 citations
TL;DR: Data indicated that increases in activities of FA transport and of lipoprotein lipase, early during cell differentiation, favored increased availability of exogenous FA at a stage when endogenous FA synthesis is limited, which would promote FA esterification and lipid deposition by supplying a rate-limiting substrate.
Abstract: An increase in early rates of oleate uptake, which reflected fatty acid (FA) entry into the cells, was apparent 2-3 days after confluence of differentiating BFC-1 preadipocytes. The increase was measured in cells kept without glucose and with arsenate, where greater than 95% of intracellular radioactivity was recovered as free unesterified oleate. Uptake of retinoic acid, a molecule structurally similar to long-chain FA, remained unaltered during cell differentiation. Increase in oleate transport was related to increase in transport Vmax (determined under arsenate treatment) from 0.2 to 2 nmol/min per 10(6) cells, whereas Km remained unchanged (2 x 10(-7) M). Oleate transport was maximal at about day 6 after cell confluence (day 0), as FA metabolism (incorporation into lipids) began to gradually increase. The increase in transport preceded induction of mRNAs for both cytosolic FA-binding protein, which appeared at day 6, and for the FA synthase, which appeared at day 10. Data indicated that increases in activities of FA transport and of lipoprotein lipase, early during cell differentiation, favored increased availability of exogenous FA at a stage when endogenous FA synthesis is limited. This result would promote FA esterification and lipid deposition by supplying a rate-limiting substrate. Furthermore, oleate addition to BFC-1 preadipocytes at confluence potentiated the effect of dexamethasone in inducing mRNA for cytosolic FA-binding protein. In adipocytes, FA from exogenous or endogenous sources was necessary to maintain levels of cytosolic FA-binding protein mRNA. Thus, the increase in FA availability might contribute to, or modulate, induction of proteins necessary for preadipocyte differentiation.
TL;DR: Findings suggest that during normoxic perfusion of rat heart H-FABPc, and LDH are released from different cellular compartments and that the bulk amount of released intracellular proteins is transported via the lymph instead of being directly released into the bloodstream.
TL;DR: Findings demonstrate that peroxisome proliferators, presumably due to their structural similarity to fatty acids, are able to bind to FABP and displace an endogenous ligand from its binding site.
Abstract: Fatty-acid-binding protein (FABP) is a 14 kDa protein found in hepatic cytosol which binds and transports fatty acids and other hydrophobic ligands throughout the cell The purpose of this investigation was to determine whether LY171883, a leukotriene D4 antagonist, and other peroxisome proliferators bind to FABP and displace an endogenous fatty acid [3H]Oleic acid was used to monitor the elution of FABP during chromatographic purification [14C]LY171883 had a similar elution profile when substituted in the purification, indicating a common interaction with FABP LY171883 and its structural analogue, LY189585, as well as the hypolipidaemic peroxisome proliferators clofibric acid, ciprofibrate, bezafibrate and WY14,643, displaced [3H]oleic acid binding to FABP Analogues of LY171883 that do not induce peroxisome proliferation only weakly displaced oleate binding [3H]Ly171883 bound directly to FABP with a Kd of 108 microM, compared with a Kd of 096 microM for [3H]oleate LY171883 binding was inhibited by LY189585, clofibric acid, ciprofibrate and bezafibrate These findings demonstrate that peroxisome proliferators, presumably due to their structural similarity to fatty acids, are able to bind to FABP and displace an endogenous ligand from its binding site Interaction of peroxisome proliferators with FABP may be involved in perturbations of fatty acid metabolism caused by these agents as well as in the development of the pleiotropic response of peroxisome proliferation
Journal Article•
TL;DR: It is suggested that H-FABP plays some fundamental roles in the active metabolism of fatty acids in the body and is a useful marker for the morphological study of interstitial cells in the ovary and testis and parietal cells inThe stomach.
Abstract: The localisation and ontogenic expression of heart fatty acid binding protein (H-FABP) were immunochemically examined in the entire body of the rat. In muscles, H-FABP immunoreactivity was observed not only in cardiac muscle cells but also in red skeletal muscles, where gold particles indicating the immunoreaction sites are distributed evenly in the sarcoplasm except for the interior of membranous organelles. In the urogenital system, the immunoreactivity was preferentially demonstrated in the distal tubular epithelial cells in the kidney, and in the superficial epithelial cells in the urinary bladder. The H-FABP immunoreactivity was further found in cells characterised by numerous lipid droplets, such as interstitial cells of the theca interna in the ovary and those of Leydig in the testis, and cell Element III in the placenta. In the digestive system, parietal cells in the stomach and pancreatic beta-cells were immunoreactive to H-FABP. In addition, capillary endothelial cells were immunostained in the cardiac and red skeletal muscles, the exocrine pancreas, digestive tract and thymus. From the rather wide distribution of H-FABP, it is suggested that H-FABP plays some fundamental roles in the active metabolism of fatty acids in the body. The present findings also indicate that H-FABP is a useful marker for the morphological study of interstitial cells in the ovary and testis and parietal cells in the stomach.
TL;DR: Results suggest strongly the functional divergence of two FABPs in the rat kidney, which shares a common ancestry with a number of hydrophobic ligand-binding proteins such as serum retinol-bindingprotein.
TL;DR: The clinical results suggest that the myocardial fatty acid influx rate is saturable by increasing fatty acid plasma concentration as well as by increasing plasma flow, which is compatible with a nondiffusional uptake process mediated by the initial interaction of fatty acids with the 40-kDa membrane fatty acid binding protein of cardiac endothelial cells.
Abstract: Fatty acid binding protein has been found in rat aortic endothelial cell membrane. It has been identified to be a 40-kDa protein that corresponds to a 40-kDa fatty acid binding protein with high affinity for a variety of long chain fatty acids isolated from rat heart myocytes. It is proposed that this endothelial membrane fatty acid binding protein might mediate the myocardial uptake of fatty acids. For evaluation of this hypothesis in vivo, influx kinetics of tracer-labeled fatty acids was examined in 15 normal subjects by scintigraphic techniques. Variation of the plasma fatty acid concentration and plasma perfusion rate has been achieved by modulation of nutrition state and exercise conditions. The clinical results suggest that the myocardial fatty acid influx rate is saturable by increasing fatty acid plasma concentration as well as by increasing plasma flow. For analysis of these data, functional relations describing fatty acid transport from plasma into myocardial tissue in the presence and absence of an "unstirred layer" were developed. The fitting of these relations to experimental data indicate that the free fatty acid influx into myocardial tissue reveals the criteria of a reaction on a capillary surface in the vicinity of flowing plasma but not of a reaction in extravascular space or in an unstirred layer and that the fatty acid influx into normal myocardium is a saturable process that is characterized by the quantity corresponding to the Michaelis-Menten constant, Km, and the maximal velocity, Vmax, 0.24 +/- 0.024 mumol/g and 0.37 +/- 0.013 mumol/g(g.min), respectively. These data are compatible with a nondiffusional uptake process mediated by the initial interaction of fatty acids with the 40-kDa membrane fatty acid binding protein of cardiac endothelial cells.
TL;DR: Induction of protein synthesis from this gene results in over expression of an FABP that is indistinguishable in its structure and binding properties with that isolated from rat liver.
Abstract: A gene coding for rat liver fatty-acid-binding protein (FABP) has been constructed by the single-step ligation of ten synthetic oligonucleotides. The gene has been cloned into the bacterial expression vector pKK223-3. Induction of protein synthesis from this gene results in over expression of an FABP that is indistinguishable in its structure and binding properties with that isolated from rat liver.
TL;DR: When a 100,000 x g supernatant from rat intestinal mucosa was incubated with 4,4'-bis([3H]methylsulfonyl)-2,2',5,5'-tetrachlorobiphenyl, a (CT3SO2)2TCB-protein complex was formed and was isolate and purified using gel filtration and ion-exchange chromatography.
TL;DR: Rat intestinal 15-kDa protein is considered to be a new member of the fatty-acid-binding protein family based on its structural features andBioactivity studies demonstrated that neither the protein nor liver and intestinal fatty- acid-binding proteins influence gastric acid secretory activity in rats with gastric fistulas compared to pentagastrin.
Abstract: An abundant and novel cytosolic protein was purified from the rat intestinal epithelium by gel filtration, ionexchange and hydroxylapatite chromatography. The protein was eluted into two different positions (fractions 1 and 2) on DEAE-cellulose chromatography. We have completed the primary structure of the protein of fraction 1 by Edman degradation. The protein (144 565 Da) contains 127 amino acid residues and has an acetylated alanine at its NH2-terminus. Comparison of the primary structure of the protein with porcine gastrotropin [Walz, A. D., Wider, M. D., Snow, J. W., Dass, C. & Desiderio, D. M. (1988) J. Biol. Chem. 263, 14189–14195] and rat hepatic fatty-acid-binding protein revealed that identical residues within these proteins are found in 90 and 54 out of a total of 127 positions, respectively.
Bioactivity studies demonstrated that neither the protein nor liver and intestinal fatty-acid-binding proteins influence gastric acid secretory activity in rats with gastric fistulas compared to pentagastrin. The protein showed very low affinity for palmitic-acid-binding in vitro assay system and only trace amounts of endogenous fatty acids were detected from the protein.
The protein, rat intestinal 15-kDa protein is considered to be a new member of the fatty-acid-binding protein family based on its structural features.
TL;DR: The coding part of the cDNA encoding human muscle fatty-acid-binding protein (FABP) was ligated in the pET8c vector and expressed under the control of the lacUV5 promoter and the physicochemical and binding characteristics of the protein were in complete agreement with those of FABP isolated from human skeletal muscle.
Abstract: The coding part of the cDNA encoding human muscle fatty-acid-binding protein (FABP) was ligated in the pET8c vector and expressed under the control of the lacUV5 promoter After induction with isopropyl beta-D-thiogalactopyranoside, almost 12% of the cytoplasmic proteins consisted of FABP The protein could be isolated after sonication of the bacterial pellet followed by (NH4)2SO4 precipitations, anion-exchange chromatography and gel filtration The muscle FABP produced in Escherichia coli has an isoelectric point of 53 and is recognized by anti-(human muscle FABP) antiserum after Western blotting The purified FABP has a preference for binding to palmitic acid and C18-C22 (poly)unsaturated fatty acids, and no affinity to palmitoyl-CoA or other hydrophobic ligands tested The dissociation constant for oleic acid is 058 microM, with a binding stoichiometry of 072 mol of fatty acid/mol of protein The physicochemical and binding characteristics of the protein were in complete agreement with those of FABP isolated from human skeletal muscle
TL;DR: Results indicate that fatty acids traverse the plasma membrane and are bound cytoplasmically by the liver fatty acid binding protein, as well as other proteins in the cell, which supports a model in which cy toplasmic lipid carriers solubilize fatty acids as a step in their metabolic utilization.
TL;DR: This review describes how a group of small, homologous, intracellular mammalian lipid-binding proteins and their genes have been ‘exploited’ over the last few years to address a number of questions in fields as diverse as biophysics and cell and developmental biology.
Abstract: This review describes how a group of small, homologous, intracellular mammalian lipid-binding proteins and their genes have been ‘exploited’ over the last few years to address a number of questions in fields as diverse as biophysics and cell and developmental biology. Their usefulness as model systems has now been recognized although their precise physiological role(s) remains a mystery.
TL;DR: Amino acid composition and pI data supported the identification of the chicken liver lipid binding proteins as L-FABP and ns-LTP, and monospecificity verified using Western blot analysis.
Abstract: 1. Two low molecular weight (approximately 14,000 Da) proteins exhibiting lipid binding activity were purified from liver cytosol and identified as non-specific lipid binding protein (ns-LTP) and fatty acid binding protein (L-FABP). 2. Ligand binding assays indicated that ns-LTP exhibited greater binding activity for cholesterol and little binding of fatty acids. Conversely, L-FABP had higher relative binding activity for fatty acids but did not bind cholesterol. 3. Amino acid composition and pI data supported the identification of the chicken liver lipid binding proteins as L-FABP and ns-LTP. 4. Polyclonal antisera was prepared against each of the liver lipid binding proteins and monospecificity verified using Western blot analysis.
TL;DR: The specificity of labeling of crude liver fractions by warfarin photoaffinity analogs reported here as well as the high concentration of FABP in liver tissue together suggest that this protein may represent a major hepatic receptor responsible for the uptake and/or transport of various oral 4-hydroxycoumarin-based anticoagulant drugs.
TL;DR: Mepacrine, a membrane stabilizer and a phospholipase inhibitor, reduced the release of H-FABP from the heart and prevented the accumulation of nonesterified fatty acids in the tissue during ischemia and reperfusion.
Patent•
18 Oct 1991TL;DR: In this paper, a method for the screening of pathological condition in the intestinal tract of an animal or a human being, e.g., intestinal ischemia, necrotizing enterocolitis, inflammatory bowel disease and bowel graft rejection, is presented.
Abstract: Disclosed is a method for the screening of pathological condition in the intestinal tract of an animal or a human being, e.g., intestinal ischemia, necrotizing enterocolitis, inflammatory bowel disease and bowel graft rejection. The method assays elevated levels of lipid binding protein, more particularly intestinal fatty acid binding protein, in a biological sample obtained from the animal or human being. Serum or urine are preferred biological samples. Preferred methods employ an immunological assay such as a radioimmunoassay or an enzyme-linked immunosorbent assay for the detection of intestinal fatty acid binding proteins in the sample.
TL;DR: Polyunsaturated fatty acyl CoA (PUFA-CoA) were thus favored for incorporation into diacyl-GPE, and to a lesser extent into diACYl- GPC, a result that is consistent with composition data.
Abstract: The acylation of 1-palmitoyl-sn-glycerophosphocholine (1-16∶0-GPC) or 1-palmitoyl-sn-glycerophosphoethanolamine (1-16∶0-GPE) was measured using the microsomal fraction prepared from retinas of 14–15-day-old chick embryos. Rates of incorporation of exogenously supplied fatty acids into diacyl-GPC were generally 5–7 times greater than into diacyl-GPE. Substrate preferences for incorporation into diacyl-GPC and diacyl-GPE were, respectively, 18∶2>18∶3=20∶5>20∶4>18∶1>22∶6=18∶0 and 18∶2>22∶6≽18∶3=18∶0≽20∶4=18∶1>20∶5. The apparent selectivities were not consistent with the reported fatty acid compositions of these lipid classes. The addition of partially purified fatty acid binding protein (FABP) to the reaction had no effect either on overall rates of incorporation or on the substrate preference. When fatty acyl-CoA substrates were used, rates of incorporation of the 18∶0 derivative were much higher than with the fatty acid, while rates with other fatty acyl-CoA were similar to those with the respective fatty acid. Substrate preferences for CoA derivatives incorporated into diacyl-GPC were: 18∶0>20∶4>18∶2≽22∶6, and into diacyl-GPE: 20∶4=22∶6>18∶0>18∶2. Polyunsaturated fatty acyl CoA (PUFA-CoA) were thus favored for incorporation into diacyl-GPE, and to a lesser extent into diacyl-GPC, a result that is consistent with composition data. When purified FABP was added to the reactions, there was an increase in the incorporation of 18∶0-CoA and a decrease or no change in the incorporation of PUFA-CoA. The deacylation/reacylation cycle thus appears to play a role in the modification of phospholipid composition. The data are not consistent, however, with a role for FABP in directing PUFA toward membrane lipid synthesis.
TL;DR: The presence of the fatty acid-binding protein in epidermal cytosol and its binding to fatty acid and retinoic acid may be of significance both in the trafficking and the metabolism of fatty acids and retinoids across the skin.
TL;DR: These studies suggest that liver fatty acid binding protein can interact with different kinds of membranes increasing specifically the desorption of fatty acids.
Abstract: Evidence is provided in this paper that indicates that fatty acids but not phospholipids are removed from microsomes or artificial membranes (liposomes, unilamellar vesicles) by mouse liver cytosolic preparations enriched with fatty acid binding protein (FABP). The cytosolic proteins can act as acceptors for fatty acids but not for phospholipids of microsomal origin. Direct evidence came when liposomes made of egg yolk phosphatidylcholine, containing both [14C]labeled phospholipids and [1-14C] palmitic acid were incubated with FABP. Using sonicated vesicles as fatty acid or phospholipid donors, mouse liver fatty acid binding protein was capable of binding palmitic acid but not phospholipids. These studies suggest that liver fatty acid binding protein can interact with different kinds of membranes increasing specifically the desorption of fatty acids.
TL;DR: It was found that isolated rat hearts preperfused with liposome-incorporated heart-type FABP, and subsequently subjected to ischemia and reperfusion developed less tissue injury than did hearts prePerfusedwith liposomes only, leading the authors to conclude that in the ischemic and reperFused myocardium FABPC exerts a protective role by the above-mentioned mechanism.
Abstract: In their recent paper Srimani et all have described a series of interesting experiments aimed at disclosing the earlier suggested2,3 possible protective role of cytoplasmic fatty acid-binding protein (FABPC) in ischemic and reperfused myocardium. The authors hypothesized that if FABPC can bind the fatty acids and thioesters accumulating intracellularly during ischemia and reperfusion, thereby preventing these compounds from exerting deleterious effects, an increase of the cellular content of FABPC might provide additional protection for ischemic and reperfusion injury. It was found that isolated rat hearts preperfused with liposome-incorporated heart-type FABP, and subsequently subjected to ischemia and reperfusion developed less tissue injury than did hearts preperfused with liposomes only. This finding led the authors to conclude that in the ischemic and reperfused myocardium FABPC exerts a protective role by the above-mentioned mechanism. However, it is our opinion that this conclusion cannot be drawn from the data presented in their article. Perfusion with liposome-incorporated FABPC would be an elegant method to elevate the content of this protein in the myocytes. In this approach it is assumed that a substantial amount of the FABPC supplied is indeed taken up by the myocytes. Unfortunately, the authors failed to demonstrate this because tissue and perfusion buffer were not analyzed for changes in FABPC content after administration of this protein. Measurement of FABPC in tissue and perfusion medium is of particular importance in the experiments described in their article, because of the substantial loss of FABPC from the myocardium after ischemia and reperfusion,4,5 a loss similar to that of creatine kinase and lactate dehydrogenase,4 which challenges the fatty acid buffering role of FABPC under these circumstances. An important finding in their study is that during the reperfusion phase coronary flow was consistently higher in FABP,-treated than in control hearts, reaching a statistically significant difference of 60% after 30 minutes of reperfusion. These differences in flow suggest that the liposome-FABP, complex exerts a vasodilating effect on the coronary vasculature. If this dilation results in enlargement of the capillary permeability surface area, it could largely explain the observed higher rate of disappearance of [1-'4C] arachidonic acid from the recirculating perfusion medium of the FABP,-treated, as compared with the untreated, hearts. Indeed, arachidonic acid uptake showed a maximal difference of 50% after 30 minutes of reperfusion. Therefore, these differences in fatty acid uptake do not necessarily reflect differences in tissue FABPC content, as stated by the authors.' An additional difficulty in assessing the true physiological value of the study is the lack of appropriate control experiments. First, no data are provided to show that the beneficial effect of FABPC is specific for this myocardial protein or that other proteins capable of non-covalent binding of long-chain fatty acids, such as albumin, would display similar protection. Second, preperfusing the hearts with non-protein-containing liposomes might already alter cardiac biochemical properties and, hence, influence the consequences of subsequent ischemia and reperfusion. Duan and Karmazyn,6 after all, have shown that addition of phosphatidylcholine to the perfusion medium enhanced the recovery of ventricular contractility of isolated rat hearts subjected to ischemia and reperfusion from about 15% to about 60% of the preischemic values. Interestingly, phosphatidylcholine was effective only when administered before the ischemic insult and in concentrations up to about 100 ^M. At higher concentrations vasoconstriction was noted.6 These authors have provided evidence that the beneficial effect of exogenous phosphatidylcholine is related to better preservation of subsarcolemmal mitochondrial function and to reduction of the toxic effect of accumulating lysophosphatidylcholine in ischemic reperfused hearts.6 Srimani et all also used phosphatidylcholine liposomes but did not mention their concentration in the perfusion medium. Therefore, it cannot be inferred whether in their experiments phosphatidylcholine exerted a protective or a coronary vasoconstricting effect on the ischemic reperfused heart. However, the marked reduction in coronary flow (25-35%) observed in both FABPc-treated and untreated hearts during the first 15 minutes of perfusion (i.e., in the presence of liposomes) indicates that coronary vasoconstriction occurred. In the case of FABP,-containing liposomes it is conceivable that the vasoconstricting effect was partially blocked. In other words, it cannot be excluded that liposomeincorporated FABPC influences the effects of constituents of the liposomal membrane on myocardium. The fact that Srimani et all found an effect only when FABPC was used before the ischemic insult is in favor of this concept. In conclusion, the possible role of cytoplasmic FABPC in sequestering excess fatty acids and esters is an interesting concept because the accumulation of these substances has been suggested to play an important role in the pathogenesis of ischemic and reperfusion injury.7 However, the study of Srimani et all provides no evidence to support or disprove the feasibility of this intriguing hypothesis. Jan F.C. Glatz Ger J. van der Vusse Robert S. Reneman Department of Physiology Cardiovascular Research Institute Maastncht University of Limburg Maastricht, The Netherlands