Biomedical subjects

E J Bechara

Publications and source records attributed to E J Bechara.

At least 37 records · Page 2Linked to original sources

PubMed1998

Neuroleptic drug-stimulated iron uptake by synaptosome preparations of rat cerebral cortex.

Neuroleptic-induced tardive dyskinesia has been linked to impaired iron homeostasis in the central nervous system attributed to increased iron levels. A chlorpromazine stimulatory effect upon iron uptake from 55Fe-citrate and 55Fe-transferrin by cortical synaptosome preparations of rats was recently demonstrated. The present work extends this study to other neuroleptic drugs such as thioridazine, haloperidol, clozapine and fluphenazine. Like chlorpromazine, thioridazine showed a stimulatory effect upon iron uptake from both iron donors whereas fluphenazine highly increased uptake from 55Fe-citrate but not from 55Fe-transferrin. Haloperidol and clozapine had no effect. Stimulation of iron uptake by neuroleptics is probably related to their property of calmodulin antagonism, since calmidazolium also stimulated synaptosomal iron uptake from both donors. Calmidazolium-stimulated uptake from 55Fe-citrate was approx. 5-fold when compared to control samples while uptake from 55Fe-transferrin was 250% higher. The results are in agreement with the iron uptake magnitude observed with the different drugs for the two iron donors used and the reported Ki values of neuroleptic drugs for calmodulin antagonism evaluated by the inhibition of 3',5'-monophosphate phosphodiesterase activity. Moreover, vanadate, an inhibitor of protein phosphorylation and KCl-promoted membrane depolarization, greatly inhibited iron uptake from 55Fe-citrate by both chlorpromazine-treated and untreated synaptosome preparations.

Animals↗

PubMed1998

Hydroxyl radicals are involved in the oxidation of isolated and cellular DNA bases by 5-aminolevulinic acid.

5-Aminolevulinic acid (ALA) is a heme precursor, pathological accumulation of which is associated with liver cancer. We show that the reactive oxygen species produced upon ALA metal-catalyzed oxidation promote the formation of several radical-induced base degradation products in isolated DNA. The distribution of modified bases is similar to that obtained upon gamma irradiation. This observation strongly suggests the involvement of hydroxyl radicals in the ALA-mediated DNA damage. Increased levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine and 5-hydroxy-2'-deoxycytidine in organ DNA of rats chronically treated with ALA were observed. This is strongly suggestive of the implication of hydroxyl radicals in the ALA-induced degradation of cellular DNA.

Aminolevulinic Acid↗

PubMed1998

Bioluminescence as a possible auxiliary oxygen detoxifying mechanism in elaterid larvae.

This work examines the hypothesis that beetle bioluminescent reactions may primarily have evolved to provide an auxiliary O2 detoxifying mechanism. The activities of antioxidant enzymes and of luciferase in the prothorax (bright) and abdomen (dim) of luminous larval Pyrearinus termitilluminans (Coleoptera: Elateridae) were measured after previous challenge with either hyperoxia, hypoxia, or the firefly luciferase inhibitor luciferin 6'-methyl ether (LME). Upon exposure to pure O2 for 72 h, the prothorax activities of total superoxide dismutase (SOD) and catalase were found to increase by 85% and 50%, respectively. Concomitantly, levels of luciferase and luciferin increased 80% and 50%. Assays of thiobarbituric acid reactive substances (TBARS) showed significantly augmented lipid peroxidation only in the abdomen (30%) where levels of antioxidant enzymes and especially luciferase are low. In contrast, exposure to hypoxia (2% O2) led to significant increases in prothorax citrate synthase (85%), succinate dehydrogenase (25%), and lactate dehydrogenase (30%) activities, but not in luciferase or antioxidant enzyme levels. LME administration alone decreased luciferase activities 20% but did not alter prothorax SOD activity. Prothorax SOD activity was increased by concomitant LME and hyperoxia treatments (30%), along with higher levels of TBARS (25%) and protein reactive carbonyl groups (50%). Altogether these data suggest that in elaterids, bioluminescence and reactions catalyzed by antioxidant enzymes may cooperate to minimize oxidative stress.

Animals↗

PubMed1998

Ruthenium red-catalyzed degradation of peroxides can prevent mitochondrial oxidative damage induced by either tert-butyl hydroperoxide or inorganic phosphate.

We have recently shown that ruthenium red, a non-competitive inhibitor of the mitochondrial Ca2+ uniporter, can reduce tert-butyl hydroperoxide via a Fenton-type reaction. In respiring mitochondrial preparations containing tert-butyl hydroperoxide, redox cycling of ruthenium red occurs and causes the amplification of methyl radical generation (Meinicke, A. R., Zavan, S. S., Ferreira, A. M. C., Vercesi, A. E., and Bechara, E. J. H. (1996) Arch. Biochem. Biophys. 328, 239-244). In this study we show that ruthenium red can act as an antioxidant preventing mitochondrial damage when the respiratory chain is reduced or when ascorbate is present. Ruthenium red can catalyze the degradation of hydrogen peroxide into H2O and O2. We show here that ruthenium red prevents both accumulation of mitochondrial generated H2O2 and swelling in the presence of the Ca2+ ionophore A23187. Under these conditions the damage induced by Ca2+ ions and either tert-butyl hydroperoxide or inorganic phosphate is promoted by mitochondrial-generated reactive oxygen species. Swelling induced by phenylarsine oxide, a thiol cross-linker, by a mechanism independent of free radicals is not inhibited by ruthenium red. These data provide evidence that the antioxidant behavior of ruthenium red under our conditions is due to its ability to destroy peroxides, which is related to its redox cycling and is prevalent over the Fenton-type reaction.

Animals↗

PubMed1998

Liposome effect on the cytochrome c-catalyzed peroxidation of carbonyl substrates to triplet species.

Cytochrome c exhibits peroxidase activity on diphenylacetaldehyde (DPAA) and 3-methylacetoacetone (MAA), which is greatly affected by the presence and nature of charged liposome or micelle interfaces interacting with the enzyme. The ferricytochrome c reaction with DPAA is accelerated when the enzyme is attached to negatively charged interfaces. Whatever the medium, bulk solution or negatively charged dicetylphosphate (DCP), phosphatidylcholine/phosphatidylethanolamine/cardiolipin (PC/PE/CL) liposomes, this chemiluminescent reaction is accompanied by reduction of cytochrome c to its ferrous form. In turn, MAA is oxidized by cytochrome c exclusively when bound to DCP liposomes. Contrary to DPAA oxidation, the MAA reaction is followed by bleaching of cytochrome c, reflecting damage to the hemeprotein chromophore. The cytochrome-c-catalyzed oxidation of either DPAA or MAA leads to concomitant disappearance of the enzyme charge transfer absorption band at 695 nm. This suggests that the peroxidase activity of cytochrome c involves substrate-induced loss of the methionine ligand at the iron sixth coordination position, which is favored by interaction of cytochrome c with negatively charged interfaces. Accordingly, a decrease and blue shift of the charge transfer band could be observed in cytochrome-c-containing negatively charged DCP, PC/PE/CL liposomes or lysophosphatidylethanolamine micelles in the presence of DPAA or MAA.

Acetaldehyde↗

PubMed1998

DNA alkylation by 4,5-dioxovaleric acid, the final oxidation product of 5-aminolevulinic acid.

The heme precursor 5-aminolevulinic acid (ALA) accumulates under pathological conditions, namely, acute intermittent porphyria (AIP) and tyrosinosis, two diseases that are associated with increased liver cancer incidence. This has been previously linked to an enhanced production of reactive oxygen species generated by a metal-catalyzed ALA oxidation process, which was shown to cause DNA single-strand breaks and guanine oxidation within both isolated and cellular DNA. In the present work, we established that the final oxidation product of ALA, 4,5-dioxovaleric acid (DOVA), is an efficient alkylating agent of the guanine moieties within both nucleoside and isolated DNA. Adducts were produced through the formation of a Schiff base involving the N2-amino group of 2'-deoxyguanosine (dGuo) and the ketone function of DOVA, respectively. The modified dGuo nucleosides were characterized, following reduction into stable secondary amines, by extensive NMR, infrared, and mass spectrometry analyses. A method, based on the use of HPLC with electrochemical detection, was then developed for the sensitive measurement of the DOVA-dGuo adducts. Using this assay, we showed that the guanine moieties of isolated DNA can undergo the same reaction as the free nucleoside. The present data provide additional information on the genotoxic potential of ALA and reinforce the hypothesis that AIP may be involved in the induction of primary liver cell carcinoma.

Alkylation↗

PubMed1998

Changes in the TBARs content and superoxide dismutase, catalase and glutathione peroxidase activities in the lymphoid organs and skeletal muscles of adrenodemedullated rats.

Thiobarbituric acid reactant substances (TBARs) content, and the activities of glucose-6-phosphate dehydrogenase (G6PDh), citrate synthase (CS), Cu/Zn- and Mn-superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPX) were measured in the lymphoid organs (thymus, spleen, and mesenteric lymph nodes (MLN)) and skeletal muscles (gastrocnemius and soleus) of adrenodemedullated (ADM) rats. The results were compared with those obtained for sham-operated rats. TBARs content was reduced by adrenodemedullation in the lymphoid organs (MLN) (28%), thymus (40%) and spleen (42%)) and gastrocnemius muscle (67%). G6PDh activity was enhanced in the MLN (69%) and reduced in the spleen (28%) and soleus muscle (75%). CS activity was reduced in all tissues (MLN (75%), spleen (71%), gastrocnemius (61%) and soleus (43%)), except in the thymus which displayed an increment of 56%. Cu/Zn-SOD activity was increased in the MLN (126%), thymus (223%), spleen (80%) and gastrocnemius muscle (360%) and was reduced in the soleus muscle (31%). Mn-SOD activity was decreased in the MLN (67%) and spleen (26%) and increased in the thymus (142%), whereas catalase activity was reduced in the MLN (76%), thymus (54%) and soleus muscle (47%). It is particularly noteworthy that in ADM rats the activity of glutathione peroxidase was not detectable by the method used. These data are consistent with the possibility that epinephrine might play a role in the oxidative stress of the lymphoid organs. Whether this fact represents an important mechanism for the establishment of impaired immune function during stress remains to be elucidated.

Adrenal Medulla↗

PubMed1997

Haem precursor delta-aminolaevulinic acid induces activation of the cytosolic iron regulatory protein 1.

Control of cellular iron homoeostasis is performed by iron regulatory protein 1 (IRP1) through post-transcriptional modifications. This protein is sensitive to intracellular iron availability, being activated at low iron levels and inactivated at high iron levels, conditions that signal the increased expression of the transferrin receptor or of ferritin respectively. IRP1 is known to be activated by some oxidants such as H2O2 and NO. delta-Aminolaevulinic acid (ALA), previously found to produce reactive oxygen species and a carbon-centred radical, to release iron from ferritin, and to increase rat liver and brain non-haem iron and ferritin, was investigated for its effects on IRP1 activity in cultured hamster pulmonary fibroblasts. We have found that 1-2 mM ALA produced a 2-3-fold activation of IRP. On incubation with 1-4 mM succinylacetone methyl ester, a potent ALA dehydratase inhibitor, a 3-4-fold activation of the protein was observed, accompanied by a 40% increase in the intracellular ALA concentration. When cells were incubated in the presence of ALA or succinylacetone methyl ester, N-acetylcysteine inhibited IRP1 activation, suggesting that the observed effect is mediated by an oxidative process. We surmise that ALA-induced IRP1 activation might act as a co-sensor of iron homoeostasis.

Acetylcysteine↗

PubMed1997

Determination of 5-aminolevulinic acid in blood plasma, tissues and cell cultures by high-performance liquid chromatography with electrochemical detection.

A simple and sensitive method for determining 5-aminolevulinic acid (ALA) in biological samples is described. ALA is derivatized with o-phthaldehyde to give a compound with favorable properties for high-performance liquid chromatography with electrochemical detection. The method does not require extensive pretreatment of the samples and its detection limit is in the range of 1 pmol/20 microl injection. This method was applied to the determination of plasma ALA from normal and lead-exposed subjects, where 0.26+/-0.08 microM (n=30) and 2.6+/-0.75 microM (n=30), respectively were found. We also determined ALA in rat tissues, namely liver and brain. and the uptake of ALA by cultured fibroblasts and hepatocytes to illustrate the diversified applicability of the method.

Air Pollutants, Occupational↗

PubMed1997

Urate protects a blood-sucking insect against hemin-induced oxidative stress.

Urate at high concentrations (up to 5 mM) is found in the hemolymph of the blood-sucking bug, Rhodnius prolixus. Increased urate levels are observed in the days following a blood meal. Injecting hemin into the hemocoel increases both urate titer and TBARS formation in the hemolymph. The urate response to hemin injection seems to arise from increased synthesis by the fat body as urate secretion by this organ is stimulated in vitro by incubation with hemin, and markedly counteracted by allopurinol. Allopurinol injection also results in increased TBARS formation in the hemolymph. High O2 atmospheric conditions also increases hemolymph urate levels, confirming that urate release represents an antioxidant response. Urate concentrations at the range reported here might account for almost all free radical scavenging activity of the hemolymph, as deduced from TRAP assay experiments, indicating that this is the major low molecular weight protection of this insect against oxidative insult. Since large amounts of hemin are produced in the midgut following blood digestion, increased urate hemolymph levels are suggested to be an important protective biochemical adaptation to allow blood feeding.

Animals↗

PubMed1997

Lipid peroxidation-dependent chemiluminescence from the cyclization of alkylperoxyl radicals to dioxetane radical intermediates.

This work reveals a novel mechanism for triplet carbonyl formation (and hence chemiluminescence) during lipid peroxidation, whose chemiluminescence has been attributed to both triplet carbonyls and singlet oxygen. As a model for polyunsaturated fatty acid hydroperoxides, we have synthesized 3-hydroperoxy-2,3-dimethyl-1-butene by photooxygenation of tetramethylethylene. One-electron oxidation of this hydroperoxide with heme proteins and peroxynitrite to the corresponding alkylperoxyl radical results in chemiluminescence, both direct and 9,10-dibromoanthracene-2-sulfonate-sensitized, the latter attributed to the formation of triplet acetone. It is postulated that triplet acetone results from the cyclization of the alkylperoxyl radical to a dioxetane radical intermediate followed by its thermolysis. This is supported by EPR spin-trapping experiments in which discrimination between carbon-centered radicals derived from the alkyloxyl and alkylperoxyl radicals is achieved through the use of one-electron oxidants and reductants, e.g., FeII- and TiIII.

Electron Spin Resonance Spectroscopy↗

PubMed1997

Oxidative tissue response promoted by 5-aminolevulinic acid promptly induces the increase of plasma antioxidant capacity.

The heme precursor 5-aminolevulinic acid (ALA), acting as a prooxidant, has been proposed to underlie the clinical manifestations of various porphyric disorders. Accordingly, ALA-generated oxyradicals where shown to cause oxidative lesions in biomolecules and isolated cell organelles and to release iron from ferritin. In rats, administered ALA triggered oxidative stress in liver, brain and red muscles. We now study the correlation between the plasma antioxidant capacity and tissue oxidative damage, after acute (one and two doses) and prolonged (eight doses) ALA treatment of rats (one dose of ALA = 40 mg/kg body weight). The in situ spontaneous chemiluminescence intensity increased 5-fold in brain, 50% in liver and 4-fold in soleus muscle upon two dose-treatment, indicating tissue response to oxidative injury by ALA. Chemiluminescence reached the highest intensity after one or two doses of ALA and decreased after eight doses in all tissues. The plasma trapping capacity, evaluated by the luminol/2-amidinopropane system, gave a parallel response: maximum values after two doses and decreased values after prolonged treatment. After eight doses, the ALA concentration was found to be 3-fold above the normal value in plasma, 48% higher in liver and 38% higher in total brain. These data indicate that the plasma antioxidant system responds to ALA treatment and is correlated with tissue chemiluminescence. In vitro studies showed that ALA does not interfere with the antioxidant plasma capacity, neither promoting oxidation of plasma elements nor binding to plasma proteins.

Amidines↗

PubMed1997

Correlation between plasma 5-aminolevulinic acid concentrations and indicators of oxidative stress in lead-exposed workers.

5-Aminolevulinic acid (ALA), a heme precursor accumulated in acute intermittent porphyria and lead poisoning, undergoes metal-catalyzed aerobic oxidation at physiological pH to yield reactive free radical species (O2., HO., and ALA.). We analyzed the relationships between plasma ALA concentrations, blood concentrations of lead, protoporphyrin IX (PP-IX), superoxide dismutase (SOD), and methemoglobin (metHb), and urine chemiluminescence (CL) in samples collected from lead-exposed workers. All variables measured were substantially (P < 0.01) higher (2-8-fold) in the lead-exposed workers (n = 60). Plasma ALA concentrations were, on average, 6-fold higher in lead-exposed workers. We observed positive linear relationships between ALA and lead (r = 0.992), ALA and PP-IX (r = 0.891), ALA and metHb (r = 0.984), lead and SOD (r = 0.948), ALA and urine CL (r = 0.987), and lead and PP-IX (r = 0.993). These data are consistent with our free radical hypothesis for lead poisoning, where ALA distribution to and accumulation in several organs may trigger oxidative stress responses.

Adolescent↗

PubMed1997

The reaction of peroxynitrite with tert-butyl hydroperoxide produces singlet molecular oxygen.

Peroxynitrite, a biological oxidant, can induce lipid peroxidation in biological membranes which leads to the formation of various hydroperoxides. Here, we report the formation of singlet oxygen (1O2) in the reaction of peroxynitrite with tert-butyl hydroperoxide (t-BOOH) used as a model compound for organic hydroperoxides. The formation of singlet oxygen was observed by (i) dimol emission in the red spectral region, (ii) monomol emission in the infrared region at 1270 nm and by (iii) chemical trapping of singlet oxygen with anthracene-9,10-diyldiethyl disulfate (EAS). The emission signal was increased when H2O was replaced by deuterium oxide and was quenched by sodium azide. When singlet oxygen was generated in the reaction of peroxynitrite with t-BOOH, the 1O2 quenching rate constant for sodium azide was estimated from a Stern-Volmer plot as 1.3 x 10(8) M(-1) S(-1) which is in line with known values. The 1O2 generation in the peroxynitrite/t-BOOH reaction was also detected by the formation of the endoperoxide of EAS. These data establish the generation of 1O2 in the reaction of peroxynitrite with t-BOOH and suggest a potential involvement of 1O2 in peroxynitrite-mediated reactions in biological systems.

Deuterium Oxide↗

PubMed1996

delta-Aminolevulinic acid-induced synaptosomal Ca2+ uptake and mitochondrial permeabilization.

delta-Aminolevulinic acid (ALA) overload is thought to be responsible for the neuropsychiatric manifestations of various porphyric disorders. In fact, ALA-generated oxyradicals have been shown to cause oxidative lesions in rat brain synaptic membranes and to decrease GABAergic receptor affinity. We now describe a stimulatory effect of ALA (1 mM) on Ca2+ uptake by cortical synaptosomes and an inhibitory effect on both transmembrane potential and oxygen consumption of intrasynaptosomal mitochondria. Both effects were partly abolished by the addition of antioxidants and the mitochondrial transmembrane potential dissipation observed to be protected by 1 microM ruthenium red. Based on these data and on the synaptosomal 14C-ALA uptake capacity, we suggest that ALA causes oxidative damage to the mitochondrial membrane. These ALA properties might be involved in the neuropsychiatric porphyric manifestations since enhanced cellular Ca2+ uptake and cerebral mitochondria dysfunction seem to be associated with several neurodegenerative processes.

Aminolevulinic Acid↗

PubMed1996

The calcium sensor ruthenium red can act as a Fenton-type reagent.

Ruthenium red (RR), an ammoniated form of tris-ruthenium(III,IV,III) oxychloride, has been widely used in the micromolar range as a strong and specific inhibitor of in vitro and in vivo Ca(2+)-mediated biochemical processes without regard for its redox properties. We show here that in the presence of tert-butyl hydroperoxide (TBHP) and an electron source, either succinate-energized rat liver mitochondria or ascorbate, RR amplifies the generation of methyl radicals. The EPR spin trapping signal of the 5,5-dimethyl-1-pyrroline-N-oxide/methyl radical (DMPO/.CH3) adduct obtained from incubations of TBHP (1.5 mM) and mitochondria (5 mg protein/ml) in an adequate medium increases upon addition of RR in a concentration-dependent fashion: sixfold at 10 microM RR. Respiring mitochondria can be replaced by ascorbate (1 mM), the characteristic EPR signal of the ascorbyl radical also being observed (aH = 0.18 mT). Spectrophotometric, cyclic voltammetric and spectroelectrochemical studies unequivocally show oxidation of RR(III,IV,III) (lambda max = 538 nm) to the ruthenium(IV,III,IV) species ("ruthenium brown," RB; lambda max = 464 nm) by TBHP, followed by its one-electron back reduction to RR by the respiratory chain or ascorbate. The calcium chelator EGTA (1 mM) strongly binds and stabilizes the RR form, slowing down its recycling by TBHP and either ascorbate or the mitochondrial electron chain. These data clearly show that Ru(III) in the RR complex can reduce TBHP via a Fenton-type reaction and thus must be considered when RR is used as a tool to study biological processes simultaneously involving Ca2+ ions and peroxides.

Animals↗

PubMed1996

Chlorpromazine stimulatory effect on iron uptake by rat brain synaptosomes.

Clinical long-term neuroleptic administration induces extrapyramidal motor side-effects, of which tardive dyskinesia is the most important. Experimentally, dopamine D2 supersensitivity is observed after phenothiazine and butyrophenone treatment. Neuroleptic-induced tardive dyskinesia and D2 modulation have been linked to impaired iron homeostasis in the central nervous system. Increased nonheme iron levels found in the basal ganglia of patients with extrapyramidal symptomology support the connection between iron and neuronal dopaminergic modulation. We now report the effect of chlorpromazine on iron uptake by synaptosomes of rat brain from two different iron donors: [55Fe]citrate and [55Fe]transferrin. Iron uptake from both donors by cortical synaptosomes was stimulated by Ca2+ and enhanced by chlorpromazine in a saturable fashion. Synaptosomes from the striatum also showed increased (60%) iron uptake from [55Fe]citrate in the presence of chlorpromazine. Chlorpromazine stimulated iron uptake by cortical synaptosomes more efficiently than Ca2+, at physiological levels, from both [55Fe]transferrin (50%) and [55Fe]citrate (68%). Calcium potentiated the effect of chloropromazine upon cortical synaptosomal iron uptake from [55Fe]citrate, but had no apparent effect on the uptake from [55Fe]transferrin. Chlorpromazine-stimulated iron uptake from the latter was observed without addition of Ca2+. Moreover, fluorescence measurement of Ca2+ uptake by cortical synaptosomes showed intensified uptake in the presence of 50 microM chlorpromazine (42%). Visible spectral studies of chlorpromazine in the presence of Fe(3+)-citrate and diferric-transferrin did not reveal iron displacement by chlorpromazine from either of the two donors. These data suggest that chlorpromazine may increase iron uptake by neurons, and may be involved in the development of tardive dyskinesia and other extrapyramidal disorders.

Animals↗

PubMed1996

Effect of inorganic phosphate concentration on the nature of inner mitochondrial membrane alterations mediated by Ca2+ ions. A proposed model for phosphate-stimulated lipid peroxidation.

Addition of high concentrations (>1 mm) of inorganic phosphate (Pi) or arsenate to Ca2+-loaded mitochondria was followed by increased rates of H2O2 production, membrane lipid peroxidation, and swelling. Mitochondrial swelling was only partially prevented either by butylhydroxytoluene, an inhibitor of lipid peroxidation, or cyclosporin A, an inhibitor of the mitochondrial permeability transition pore. This swelling was totally prevented by the simultaneous presence of these compounds. At lower Pi concentrations (1 mm), mitochondrial swelling is reversible and prevented by cyclosporin A, but not by butylhydroxytoluene. In any case (low or high phosphate concentration) exogenous catalase prevented mitochondrial swelling, suggesting that reactive oxygen species (ROS) participate in these mechanisms. Altogether, the data suggest that, at low Pi concentrations, membrane permeabilization is reversible and mediated by opening of the mitochondrial permeability transition pore, whereas at high Pi concentrations, membrane permeabilization is irreversible because lipid peroxidation also takes place. Under these conditions, lipid peroxidation is strongly inhibited by sorbate, a putative quencher of triplet carbonyl species. This suggests that high Pi or arsenate concentrations stimulate propagation of the peroxidative reactions initiated by mitochondrial-generated ROS because these anions are able to catalyze Cn-aldehyde tautomerization producing enols, which can be oxidized by hemeproteins to yield the lower Cn - 1-aldehyde in the triplet state. This proposition was also supported by experiments using a model system consisting of phosphatidylcholine/dicethylphosphate liposomes and the triplet acetone-generating system isobutanal/horseradish peroxidase, where phosphate and Ca2+ cooperate to increase the yield of thiobarbituric acid-reactive substances.

Acetates↗