Biomedical subjects

B Rüstow

Publications and source records attributed to B Rüstow.

At least 19 recordsLinked to original sources

PubMed2002

Ectoprotein kinase-mediated phosphorylation of FAT/CD36 regulates palmitate uptake by human platelets.

Glycoprotein IV (FAT/CD36) has been shown to be phosphorylated by a cAMP-dependent, platelet membrane-bound ectokinase. In this study, we demonstrate that ectophosphorylation of FAT/CD36 regulates initial palmitate uptake. This is the first time that short-term regulation of the activity of a long-chain fatty acid carrier could be shown. Phosphorylation of FAT/CD36 was paralleled by a significant decrease in initial palmitate uptake by morphologically and functionally intact platelets. Maximum inhibition of palmitate uptake was achieved at 0.5 nM extracellular ATP, being significantly decreased to 72% compared to the control. Inhibition of palmitate uptake was abolished by co-incubation with the specific protein kinase A inhibitor peptide PKI or with beta,gamma-methylene-ATP, and was reversible upon addition of alkaline phosphatase. An extracellular ATP concentration above 5 microM completely prevented the ectophosphorylation-mediated inhibition of palmitate uptake. We conclude that FAT/CD36-mediated palmitate uptake by human platelets is short-term regulated via cAMP-dependent ectophosphorylation of FAT/CD36.

Blood Platelets↗

PubMed2001

Platelet-activating factor (PAF)-acetylhydrolase and PAF-like compounds in the lung: effects of hyperoxia.

Platelet-activating factor (PAF)-acetylhydrolase is the enzyme modulating in tissues and biological fluids the concentration of the proinflammatory factors PAF and PAF-like oxidation products of phospholipids (PAF-like compounds). We investigated whether there is a relation between PAF-acetylhydrolase activity and the concentration of PAF-like compounds in bronchoalveolar lavage (BAL). We found that alveolar type II cells are an additional source of PAF-acetylhydrolase in BAL beside macrophages. Secretion of PAF-acetylhydrolase was stimulated by phorbol ester in alveolar type II cells but not in macrophages. Studies in BAL suggested that secreted PAF-acetylhydrolase was bound to alveolar surfactant. Exposure of rats to high oxygen concentration reduced the activity of PAF-acetylhydrolase in BAL and macrophages, but not in plasma or alveolar type II cells. In contrast, hyperoxia increased the concentration of PAF-like-compounds, lipid hydroperoxides and malonedialdehyde in plasma but not in BAL. Therefore, we conclude that neither the oxidant-induced decrease of the PAF-acetylhydrolase activity nor the direct peroxidation of surfactant lipids in the alveoli provide a likely mechanism for hyperoxia-induced lung injury. Instead, lung injury is apparently caused by lipid peroxidation in plasma rather than by high oxygen pressure in the alveoli.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2001

Immunological dysregulation of lung cells in response to vitamin E deficiency.

Vitamin E supplementation exhibits anti-inflammatory properties. In the lung, the beneficial effects of vitamin E supplementation on inflammation and infections are well documented, but potential consequences of alimentary vitamin E deficiency to the immunological status of lung cells are not known. It is unclear if temporary vitamin E deficiency exhibits deleterious consequences or can be compensated for by other cellular antioxidants. To address this question, the alimentary vitamin E supply to rats was modified. We then investigated the effects on major histocompatibility molecule (MHC) class II, cell adhesion molecules, interleukin (IL)10, tumor necrosis factor (TNF)alpha in various lung cells. The constitutive expression of MHC class II, intercellular adhesion molecule (ICAM)-1, L-selectin, alpha5-integrin, and CD 166, was demonstrated by flow cytometry on type II pneumocytes, alveolar macrophages, and on co-isolated lymphocytes. Vitamin E depletion increased ICAM-1 and CD166 on type II cells and macrophages, whereas the expression of L-selectin increased only on macrophages. Furthermore, the vitamin E depletion increased the cellular content and secretion of IL10 in type II cells, but decreased the content and secretion of TNFalpha. Vitamin E depletion decreased the cellular vitamin E content, but did not change the activity of antioxidant enzymes (catalase, superoxide dismutase) and the glutathion (GSH)/oxidized glutathion (GSSG) ratio in alveolar type II cells. The shift of protein kinase C (PKC) from the cytosol to membranes indicates that a PKC-dependent signaling pathway may be involved in the change of the immunological status of type II cells. All these effects were reversed by vitamin E repletion. In summary, these results are clearly compatible with the view that a temporary vitamin E deficiency induces a reversible immunological dysregulation in alveolar type II cells and lung macrophages. This deficiency might predispose the lung to develop acute or chronic inflammation.

Animals↗

PubMed2001

Disturbed surface properties in preterm infants with pneumonia.

Congenital pneumonia in preterm infants is often associated with respiratory insufficiency requiring mechanical ventilation. This study was performed to show whether pneumonia in these infants is associated with an inhibition or deficiency of surfactant. The ratio of lecithin and sphingomyelin (L/S ratio) and minimal surface tension were determined in pharyngeal aspirates from 90 term born infants (healthy) and in tracheal aspirates from preterm infants with wet lung (n = 13), congenital pneumonia (n = 21) and respiratory distress syndrome (RDS) (n = 90). The L/S ratio was lower (p < 0.0001) in the RDS group (8.6) when compared with healthy (48.6), wet lung (42.9) and pneumonia (28.9). Surface tension was higher (p < 0.001) in RDS (37 mN/m) and pneumonia (33.7) when compared with healthy (22.9) or wet lung (21.2). For infants with RDS, L/S ratio <16.5 detects surfactant deficiency with 96% specificity and 70% sensitivity, surface tension >29 mN/m represents surfactant inhibition (specificity 97%, sensitivity 92%). Using these cut-off values in infants with pneumonia, 81% had a sufficient amount of surfactant but only 21% of infants with pneumonia had appropriate surface tension. Our study shows that lung effluent of respiratory insufficient infants with pneumonia, who need mechanical ventilation, has disturbed surface properties despite a sufficient amount of surfactant. In these infants, surfactant substitution could be beneficial.

Case-Control Studies↗

PubMed2000

An electrophoretic study of vitamin E status and expression of heat shock proteins in alveolar type II and liver cells.

Vitamin E is the most important lipophilic antioxidant. Oxidative injuries are prevented or minimized by vitamin E supplementation. Various physiological and pathological situations are accompanied by vitamin E deficiency. However, it is not clear whether alimentary vitamin E deficiency in itself constitutes oxidant stress that induces appropriate responses, which, in turn, can be avoided by adequate vitamin E supplies, or whether the remaining cellular antioxidants compensate a temporary vitamin E deficiency. We studied effects of the dietary vitamin E status on cellular vitamin E levels and on the expression of heat shock proteins (HSPs) in alveolar type II cells and liver. The expression of HSPs, representing an early and very sensitive marker of cellular stress, was compared with the activity of antioxidative enzymes. Vitamin E depletion caused a substantial increase in HSP32 in alveolar type II cells, whereas in liver there was a marked increase in HSP70. The activity of the antioxidant enzymes, however, did not change significantly. A reversal of HSP expression to almost normal levels was seen after vitamin E resupplementation. These results indicate that, under normal conditions, a suboptimal supply of vitamin E to rats exposes the alveolar type II cells and the liver to reversible cellular stress.

Animals↗

PubMed2000

HDL and vitamin E in plasma and the expression of SR-BI on lung cells during rat perinatal development.

Vitamin E is the most important lipophilic antioxidant, and beneficial effects on oxidant-caused injuries have been reported. Neonates are at high risk of oxidative injury in the lung and other organs because of a low vitamin E concentration, but the optimal timing of the application, a safe application form, and the optimal dosage of vitamin E are not known at present. We recently showed that alveolar type II cells take up vitamin E preferentially from high-density lipoprotein (HDL), probably by means of the candidate HDL receptor, scavenger receptor class B type I (SR-BI; Kolleck et al. Free Rad Biol Med 27; 882-890, 1999). Therefore, both the HDL-bound vitamin E in plasma and the expression of SR-BI on alveolar type II cells may determine the supply of the cells with vitamin E. We show here that the plasma level of vitamin E, total and HDL cholesterol, and the ratio of vitamin E to polyunsaturated fatty acids and to total fatty acids decrease during fetal rat development, reaching the minimum at the postconceptual day 21 (day -1). These parameters increase thereafter to about the same levels as in adult rats. SR-BI is not detectable until day -1 on fetal lung cells, but the expression during the postnatal phase follows the same pattern as the plasma lipid constituents. We conclude that the ability of alveolar type II cells to take up vitamin E develops perinatally in mature neonates. This aspect also has to be considered when the optimal timing of supplementation for the protection of preterm neonates with vitamin E against oxidative lung injury is established.

Animals↗

PubMed2000

Heparin induces release of phospholipase A(2) into the splanchnic circulation.

UNLABELLED: Cardiopulmonary bypass results in increased plasma activity of phospholipase A(2) (PLA(2)) that appears to be caused by the administration of heparin. High PLA(2) activity may be responsible for increased production of eicosanoids and, thus, may be implicated in various pathophysiologic events associated with cardiac surgery. To investigate the site of PLA(2) secretion, blood samples were simultaneously collected from the radial artery, the pulmonary artery, and the hepatic vein at 2, 4, 6, and 20 min after systemic heparinization (350 U/kg). Within 2 min of the heparin injection, plasma activity of PLA(2) increased 4- to 9-fold and remained so for at least 20 min. Two minutes after the heparin injection, PLA(2) was significantly higher in the hepatic vein than in the radial artery (P: < 0.01). No such difference was detected between pulmonary and radial arteries. When heparin was added to blood samples in vitro (5-100 U/mL), plasma activity of PLA(2) did not increase, which suggests that the enzyme was not secreted by blood cells. IMPLICATIONS: Heparin, given in the dosage required for cardiopulmonary bypass, caused release of phospholipase A(2) into the splanchnic circulation.

Aged↗

PubMed2000

Preterm infants with high polyunsaturated fatty acid and plasmalogen content in tracheal aspirates develop bronchopulmonary dysplasia less often.

OBJECTIVE: Oxygen toxicity causes chronic bronchopulmonary dysplasia (BPD) in extremely preterm infants. Polyunsaturated fatty acids (PUFA) and plasmalogens are the two main substrates for lipid peroxidation in the pulmonary surfactant. In the present study, we tested whether low concentrations of both were associated with development of BPD and whether both were further reduced during mechanical ventilation with oxygen. DESIGN: Prospective, noninterventional, descriptive study. SETTING: Level III neonatal intensive care unit in a university hospital. PATIENTS: In 25 extremely low birth weight infants with respiratory distress syndrome, tracheal aspirates were collected immediately after birth and in the following 4 days. As control, tracheal and pharyngeal aspirates were collected from healthy infants immediately after birth. The amount of PUFA and dimethylacetals (DMA, representing plasmalogens) was determined gas-chromatographically. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The relative percentages of PUFA and DMA on all fatty acids in non-BPD infants (PUFA% 26+/-8.9, DMA% 3.5+/-1.2) were higher compared with infants who developed BPD (PUFA% 14.5+/-3.8, DMA% 1.8+/-0.9). In term healthy infants, DMA% and PUFA% were in the same range as in the BPD group. The higher levels found for non-BPD infants decreased after day 1 to values equal to the BPD group and remained low. CONCLUSIONS: The results suggest that initially higher levels of PUFA and plasmalogens in the tracheal effluent are associated with a reduced risk of developing BPD and are reduced during the first day of ventilation.

Bronchopulmonary Dysplasia↗

PubMed2000

Identification of high density lipoprotein-binding proteins, including a glycosyl phosphatidylinositol-anchored membrane dipeptidase, in rat lung and type II pneumocytes.

Numerous communications have indicated that specific binding proteins for high density lipoprotein (HDL) exist in addition to the well characterized candidate HDL receptor SR-BI, but structural information was presented only in a few cases, and most of the work was aimed at the liver and steroidogenic glands. In this study, we purified two HDL-binding proteins by standard procedures from rat lung tissue. One of these membrane glycoproteins was identified by N-terminal sequencing and with specific antibodies as HB2, a previously described HDL-binding protein, whereas the other one was identified as a glycosyl phosphatidylinositol-anchored membrane dipeptidase (MDP). The apparent dissociation constant of the HDL binding was determined by solid phase assay to be 2.1 microg/ml (HB2) and 25 microg/ml (MDP). MDP also exerts affinity to low density lipoprotein (LDL) on ligand blots, and competition between HDL and LDL was observed, but analysis by solid phase assay showed that very high concentrations of LDL are required. The physiologic relevance of this effect is therefore questionable. The level in type II pneumocyte membranes of both binding proteins, MDP and HB2, increased when the plasma lipoprotein concentration was reduced by treatment of rats with 4-aminopyrazolo[3,4-d]-pyrimidine, consistent with a function to facilitate lipid uptake in vivo. The binding proteins were also dramatically upregulated by feeding rats a vitamin E-depleted diet. Vitamin E uptake requires interaction between HDL and type II cells, suggesting a role of HB2 and MDP also in this process.

Amino Acid Sequence↗

PubMed2000

Increase in fragmented phosphatidylcholine in blood plasma by oxidative stress.

Oxidatively modified phospholipids with fragmented acyl chains have attracted much interest because of their proinflammatory activity and their potential involvement in atherosclerosis. They can be formed in vitro by free radical treatment of unsaturated phospholipids but it is not known under which conditions they accumulate in vivo. We assayed one species of fragmented phosphatidylcholine (PC) in human blood plasma by high performance liquid chromatography after precolumn derivatization with chloromethylanthracene. Structural analysis suggested that fragmented PC was a diacyl species with a palmitoyl group and a short oxidized residue, which most likely had four carbons. The concentration of fragmented PC was higher in elderly individuals with coronary heart disease than in young healthy controls. Smoking one cigarette acutely increased the concentration of fragmented PC in healthy adults. Fragmented PC also increased in the reperfusion period after treatment with cardiopulmonary bypass. The increase coincided with a surge of circulating neutrophils. In rats, the plasma concentration of fragmented PC was elevated by vitamin E deficiency and exposure to high oxygen. The data demonstrate that fragmented PC increases in blood plasma in response to various forms of oxidative stress.

Adult↗

PubMed2000

Regulation by vitamin E of the scavenger receptor BI in rat liver and HepG2 cells.

The scavenger receptor class B type I (SR-BI) mediates the selective uptake of cholesterol and cholesteryl ester (CE) from high density lipoprotein (HDL) into cells. The high expression in liver and steroidogenic tissues is compatible with a role of SR-BI in reverse cholesterol transport and steroid hormone synthesis. Ways of regulation thus far described include induction by trophic hormones via cAMP-activated protein kinase A (PKA) and the effects of cellular and plasma cholesterol. Here we show that vitamin E (vitE) has a major effect on the expression of SR-BI in rat liver and in a human hepatoma-derived cell line, HepG2. Feeding rats a vitE-depleted diet resulted in an 11-fold increase in the SR-BI protein level in liver tissue. This effect was readily reversed by feeding a vitE-enriched chow. In HepG2 cells, the expression of the human SR-BI homolog was reduced when the vitE content was increased by incubating the cells with vitE-loaded HDL or with phosphatidylcholine/vitE vesicles. The downregulation of human SR-BI (hSR-BI) was accompanied by a reduced level of protein kinase C (PKC) in the particulate cell fraction, and PKC inhibition decreased the expression of hSR-BI and the uptake of vitE and cholesterol from HDL. Our results are consistent with the view that the cellular level of vitE exerts a tight control over the expression of SR-BI. Furthermore, the inhibitory effect of vitE on PKC seems to be involved in the signaling pathway.

Animals↗

PubMed1999

Expression, purification, and crystal structure determination of recombinant human epidermal-type fatty acid binding protein.

We describe the crystal structure of human epidermal-type fatty acid binding protein (E-FABP) that was recently found to be highly upregulated in human psoriatic keratinocytes. To characterize E-FABP with respect to ligand-binding properties and tertiary structure, we cloned the respective cDNA, overexpressed the protein in Escherichia coli and purified it to homogeneity by a combination of ion-exchange and size-exclusion chromatographic steps with a yield of 30 mg/L broth. The purified protein revealed a 5-fold higher affinity for stearic acid than for oleic and arachidonic acids. The crystal structure of recombinant human E-FABP was determined to 2.05 A and refined to an R(factor) of 20.7%. The initial residual electron density maps clearly showed the presence of a ligand, which was identified as endogenous bacterial fatty acid. Within a central cavity of 252 A(3), this ligand is bound in a U-shaped conformation, its carboxyl group interacting with tyrosine 131 and arginines 129 and 109, the latter via an ordered water molecule. The E-FABP crystal structure is unique in the FABP family because of the presence of a disulfide bridge between cysteines 120 and 127 that may be physiologically as well as pathophysiologically relevant. Cysteines 67 and 87 are also in close vicinity but in contrast do not form a disulfide bridge. We postulate that this protein belongs to a particular FABP subfamily whose members share common structural as well as functional features.

Adipose Tissue↗

PubMed1999

HDL is the major source of vitamin E for type II pneumocytes.

The alveolar surfactant is a prime target of reactive oxygen species present in air. Alveolar surfactant is supplemented with vitamin E during its assembly in type II pneumocytes. However, it is unknown which of the lipoproteins supply type II pneumocytes with vitamin E. The measurement of the uptake kinetics indicates that HDL might be the primary source of the vitamin E uptake by type II pneumocytes. Vitamin E depletion of rats caused an increase of vitamin E uptake by isolated type II pneumocytes from HDL but not from LDL or VLDL. We demonstrated that type II pneumocytes express the scavenger receptor class B type 1 (SR-B1), an HDL-specific receptor. Vitamin E depletion caused an increased expression of SR-B1 by a post-transcriptional mechanism. The increased vitamin E uptake from HDL and the increased expression of the SR-B1 were reversed by refeeding the vitamin. We propose that HDL is the primary source of vitamin E for type II pneumocytes. The rate of uptake of vitamin E by this cell type might be regulated by the expression of SR-B1.

Animals↗

PubMed1999

Fatty acid translocase/CD36 mediates the uptake of palmitate by type II pneumocytes.

Type II pneumocytes, which synthesize, store, and secrete pulmonary surfactant, require exogenous fatty acids, in particular palmitic acid, for maximum surfactant synthesis. The uptake of palmitate by type II pneumocytes is thought to be protein mediated, but the protein involved has not been characterized. Here we show by RT-PCR and Northern blot analysis that rat type II pneumocytes express the mRNA for fatty acid translocase (FAT/CD36), a membrane-associated protein that is known to facilitate the uptake of fatty acids into adipocytes. The deduced amino acid sequence from rat type II pneumocytes reveals 98% identity to the FAT/CD36 sequence obtained from rat adipocytes. The uptake of palmitate by type II pneumocytes follows Michaelis-Menten kinetics (Michaelis-Menten constant = 11.9 +/- 1.8 nM; maximum velocity = 62.7 +/- 5.8 pmol. min(-1). 5 x 10(5) pneumocytes(-1)) and decreases reversibly under conditions of ATP depletion to 35% of control uptake. Incubation of cells at 0 degrees C inhibited the uptake of palmitate almost completely, whereas depletion of potassium was without effect. Preincubation of the cells with bromobimane or phloretin decreases the uptake of palmitate significantly as does preincubation with sulfo-N-succinimidyl oleate, the specific inhibitor of FAT/CD36 (C. M. Harmon, P. Luce, A. H. Beth, and N. A. Abumrad. J. Membr. Biol. 121: 261-268, 1991). From these data, we conclude that FAT/CD36 is expressed in type II pneumocytes and mediates the uptake of palmitate in a saturable and energy-dependent manner. The data suggest that the uptake process is independent of the formation of coated pits and endocytotic vesicles.

Amino Acid Sequence↗

PubMed1998

Stimulation of monocytes and platelets by short-chain phosphatidylcholines with and without terminal carboxyl group.

Oxidation of unsaturated phosphatidylcholine (PC) produces fragmented phospholipids which have similar bioactivities as the platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-PC). Since a large number of molecular species are produced upon PC oxidation, the active ingredients have not been identified. We synthesized several short-chain PCs which are known to be characteristic PC oxidation products to test their PAF-like activity. The synthetic PCs contained palmitoyl or hexadecyl residues (both C16) in sn-1 position, and propionyl (C3), valeroyl (C5), succinyl (C4 with omega-carboxyl), glutaroyl (C5 with omega-carboxyl), or suberoyl (C8 with omega-carboxyl) residues in sn-2 position. Biological activity was measured by: (1) increase of intracellular calcium in human monocytes; (2) [3H]serotonin release from rabbit platelets; and (3) aggregation of human platelets. Specificity of the cellular response was tested by inhibition with the PAF-receptor antagonists BN 52021 and WEB 2086. Synthetic PC oxidation products activated both monocytes and platelets in a PAF-specific manner. The effective concentration varied with respect to assay system and chemical structure. In general, 1-hexadecyl-PCs were more effective than 1-palmitoyl-PCs, while increasing chain length in sn-2 position lowered biological activity. However, several 1-palmitoyl-PCs activated monocytes in concentrations between 10-8 and 10-6 M. In contrast, platelets were less susceptible to 1-palmitoyl-PCs. No significant difference was found between 2-valeroyl-PC (C5 with omega-methyl) and 2-glutaroyl-PC (C5 with omega-carboxyl). The data suggest that typical products of PC oxidation, containing propionyl, succinyl, or glutaroyl residues in sn-2 position, display PAF-like activity at micromolar concentrations.

Animals↗

PubMed1998

Cloning and chromosomal localisation of the murine epidermal-type fatty acid binding protein gene (Fabpe).

We succeeded in cloning the gene encoding the murine epidermal-type fatty acid binding protein (E-FABP). To avoid the screening of pseudogenes, the presence of which was shown by PCR, we designed an intron-specific probe and screened a bacterial artificial chromosome library from mouse embryonic stem cells. One of the clones obtained was analysed by restriction with various enzymes and an 11-kb EcoRI fragment with the complete gene was subcloned. The gene revealed the canonical exon/intron FABP structure consisting of four exons (112, 173, 102 and 544bp, respectively) and three introns (2217, 327 and 546bp, respectively). The exon sequences were identical with the cDNA encoding mouse E-FABP (Krieg, P., Feil, S., Fürstenberger, G., Bowden, T.G., 1993. Tumor-specific overexpression of a novel keratinocyte lipid-binding protein. Identification and characterisation of a cloned sequence activated during multistage carcinogenesis in mouse skin. J. Biol. Chem. 268, 17362-17369). Of the 5' region, 2470bp were sequenced and searched for transcription factor binding sites. Putative responsive elements within the promoter region were identified that may be responsible for the wide expression observed for E-FABP in mouse tissues. The 11-kb EcoRI fragment was used to localise Fabpe on chromosome 3 in the region 3A1-3 by fluorescence in-situ hybridisation.

Amino Acid Sequence↗

PubMed1998

alpha- and delta-tocopherol induce expression of hepatic alpha-tocopherol-transfer-protein mRNA.

alpha-Tocopherol transfer protein (alpha-TTP) supplements nascent very-low-density lipoprotein (VLDL) preferentially with alpha-tocopherol by selecting the alpha-isomers against other stereoisomers of tocopherol. It is exclusively expressed in liver. We investigated whether the expression of the hepatic alpha-TTP can be induced by dietary tocopherols. Vitamin E-depleted rats were fed with a diet containing alpha- and delta-tocopherol (ratio 1:3). The expression of alpha-TTP mRNA was measured in liver tissue. The ratio of tocopherol stereoisomers was determined in plasma, plasma lipoproteins and tissues to measure the metabolic action of alpha-TTP. Refeeding a diet containing either alpha- or delta-tocopherol, or both, caused a steady increase of the expression of alpha-TTP mRNA. In parallel the alpha/delta-tocopherol ratio increased in plasma, VLDL, high-density lipoprotein and low-density lipoprotein as well as in liver tissue, when the diet was fed containing both isomers. The alpha-tocopherol/delta-tocopherol ratio of heart, kidney, lung, lamellar bodies of lung and in lung lavage showed no or a comparatively low increase. The data show that both tocopherol isomers were able to induce alpha-TTP mRNA in rat liver and, thus, the ability of liver to select for the alpha-isomer. On the other hand, tocopherol depletion did not change the expression of hepatic alpha-TTP mRNA in the rat.

Animals↗

PubMed1998

Expression of fatty-acid-binding proteins in cells involved in lung-specific lipid metabolism.

Members of the fatty-acid-binding protein (FABP) family are thought to play an important role in fatty acid transport within the cytosol and thus to be involved in lipid metabolism. As previous data on the occurrence of distinct FABP types in total lung are contradictory, we determined the expression of FABP types in three isolated cell types of rat lung, which are characterised by active lipid metabolism. Alveolar type-II cells synthesise, store and secrete pulmonary surfactant, a phospholipid-rich surface-tension-lowering agent, whereas lung fibroblasts, localised adjacent to the alveolar type-II cells, are assumed to provide neutral lipid substrate to alveolar type-II cells around birth, and alveolar macrophages are known to degrade complex lipids. Initial screening by reverse transcriptase PCR revealed the occurrence of heart (H-), epidermal (E-) and liver FABP in rat lung, the latter being not detectable in the three cell types studied. Cells were analysed by northern and western blotting, then quantitatively by sandwich ELISA, for which recombinant rat E-FABP was prepared. E-FABP mRNA was found in all three cell types, and E-FABP was detected in the following amounts: 240.9 +/- 19.0 ng/mg cytosolic protein in alveolar type-II cells; 172.3 +/- 0.7 ng/mg protein for lung fibroblasts; and 36.9 +/- 3.5 ng/mg protein for alveolar macrophages. This indicates a basic function of E-FABP in cellular lipid metabolism. In contrast, H-FABP probably is involved in the metabolism of neutral lipids because H-FABP mRNA was found only in lung fibroblasts with a corresponding protein level of 315.5 +/- 6.9 ng/mg. Small amounts of H-FABP protein were present in alveolar type-II cells and alveolar macrophages.

Animals↗