Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pyruvates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,351 records · Page 75Linked to original sources
PubMed1999

Attenuation of sugar cataract by ethyl pyruvate.

Studies describe an attenuation of sugar cataract formation by topical administration of ethyl pyruvate. Cataract formation was induced by feeding young rats a 30% galactose diet. Mature cataracts appeared in about thirty days. Instillation of the eye drops containing 5% ethyl pyruvate decelerated the process significantly. Biochemically, the effect was reflected by lowering in the contents of dulcitol and glycated proteins. The ATP levels were also higher in comparison to the placebo treated group. The effects are hence attributable to the effect of pyruvate in inhibiting dulcitol synthesis and protein glycation, in addition to its antioxidant properties and metabolic support. The use of esterified pyruvate instead of the unesterified pyruvate was preferred because of its greater penetration through the cornea and consequently a higher concentration attained in the aqueous humor.

Adenosine Triphosphate↗
PubMed2003

Alanine prevents the inhibition of pyruvate kinase activity caused by tryptophan in cerebral cortex of rats.

Hypertryptophanemia is a rare inherited metabolic disorder probably caused by a blockage in the conversion of tryptophan to kynurenine, accumulating tryptophan and some of its metabolites in plasma and tissues of affected patients. The patients present mild to moderate mental retardation with exaggerated affective responses, periodic mood swings, and apparent hypersexual behavior. Pyruvate kinase catalyses a critical step in the glycolysis pathway, the main route that provides energy to brain functioning. The main objective of the present study was to determine pyruvate kinase activity in brain cortex of rats subjected to acute chemically induced hypertryptophanemia. The effect of alanine administration to the treated rats on the enzyme activity was also investigated. We also studied the in vitro effect of the two amino acids on pyruvate kinase activity in the brain cortex of nontreated rats. The results indicated that tryptophan inhibits pyruvate kinase in vitro and in vivo and that alanine prevents this inhibitory effect on the enzyme activity. Considering the crucial role pyruvate kinase plays in glucose metabolism in brain, it is possible that inhibition of this enzyme activity may contribute to the brain damage characteristic of this disease. Further studies will be necessary to evaluate possible benefits of alanine administration to the patients affected by hypertryptophanemia.

Alanine↗
PubMed1968

Pyruvate metabolism by aminopterin-inhibited Aerobacter aerogenes.

1. The synthesis and utilization of both alanine (by reductive amination, oxidative deamination and transamination) and valine (by transamination only) in Aerobacter aerogenes are unaffected by aminopterin. These amino acids, which accumulate in aminopterin-treated cultures of this organism, are therefore considered to be formed as secondary products from the excess of pyruvate that also accumulates. 2. Oxidative metabolism of pyruvate and the synthesis of acetylmethylcarbinol by A. aerogenes cells are unaltered by growth in the presence of aminopterin. 3. Cells from static and anaerobic cultures that have been treated with the folic acid antagonist in the early exponential phase have a decreased ability to cleave pyruvate to acetate and formate, and to effect the exchange of formate with the carboxyl group of pyruvate. 4. 3-Methyl-2-oxobutanoate, the keto acid precursor of valine, cannot replace pyruvate as substrate in either the phosphoroclastic or the exchange reaction.

Alanine↗
PubMed1968

Pyruvate accumulation in growth-inhibited cultures of Aerobacter aerogenes.

1. Accumulation of pyruvate occurs during the early stages of exponential growth of aerobic, anaerobic and static cultures of a strain of Aerobacter aerogenes. In normal cultures of this organism the content of pyruvate increases until most of the glucose of the medium has been consumed, and then declines rapidly. The presence of unconsumed sugar is not the sole reason for the accumulation of keto acid, since this is unaffected by the addition of extra glucose to either exponentialphase or stationary-phase cultures. 2. In aminopterin-inhibited cultures, the rate of glucose utilization is decreased greatly, and pyruvate continues to accumulate throughout the period of incubation. This prolonged phase of accumulation appears to be a consequence of the growth inhibition, and not to a specific action of aminopterin on the phosphoroclastic breakdown of pyruvate, since it occurs also when growth is restricted by the antibiotics streptomycin, chloramphenicol and neomycin. 3. A possible explanation is suggested for the accumulation of pyruvate in the inhibited cultures.

Aminopterin↗
PubMed1968

Effect of atractyloside on glucose and pyruvate metabolism in rat diaphragm muscle.

1. In the presence of 1.2mm-atractyloside oxygen uptake by rat diaphragm muscle incubated with 5.6mm-glucose decreases, as well as glycogen synthesis and carbon dioxide production. Lactate formation from glucose increases, but that of phosphoglycerate diminishes fivefold. 2. When pyruvate is used as substrate, atractyloside decreases oxygen uptake. 3. The specific radioactivity of the (14)CO(2) (mumoles of (14)CO(2)/mumole of oxygen), calculated at concentrations of [1-(14)C]pyruvate between 0.091mm and 91mm, lies between 3.1x10(-4) and 5.7x10(-1). Atractyloside increases the specific radioactivity of the (14)CO(2) with the lowest concentrations of substrate and has no effect when the substrate concentration is 91mm. 4. No appreciable effect of atractyloside on the anaerobic production of (14)CO(2) from [1-(14)C]pyruvate at various incubation times and various concentrations is found. 5. It is suggested that atractyloside induces anaerobic conditions in the tissue. Further, it produces a rise in the pyruvate concentration and an ATP deficiency in the cell. Consequently it stimulates pyruvate dismutation, and glycolysis, to which phosphorylation is linked at the substrate level.

Adenosine Triphosphate↗
PubMed1969

Effects of adenosine phosphates and nicotinamide nucleotides on pyruvate carboxylase from baker's yeast.

1. Pyruvate carboxylase from baker's yeast is inhibited by ADP, AMP and adenosine at pH8.0 in the presence of magnesium chloride concentrations equal to or higher than the ATP concentration. The adenine moiety is essential for the inhibitory effect. 2. In the absence of acetyl-CoA (an allosteric activator) ADP, AMP and adenosine are competitive inhibitors with respect to ATP. In the presence of acetyl-CoA, besides the effect with respect to ATP, AMP competes with acetyl-CoA, whereas ADP and adenosine are non-competitive inhibitors with respect to the activator. 3. Pyruvate carboxylase is inhibited by NADH. The inhibition is competitive with respect to acetyl-CoA and specific with respect to NADH, since NAD(+), NADP(+) and NADPH do not affect the enzyme activity. In the absence of acetyl-CoA, NAD(+), NADH, NADP(+) and NADPH do not inhibit pyruvate carboxylase. 4. Pyruvate carboxylase is inhibited by ADP, AMP and NADH at pH6.5, in the presence of 12mm-Mg(2+), 0.75mm-Mn(2+) and 0.5mm-ATP, medium conditions similar to those existing inside the yeast cell. The ADP and NADH effects are consistent with a regulation of enzyme activity by the intracellular [ATP]/[ADP] ratio and secondarily by NADH concentration. These mechanisms would supplement the already known control of yeast pyruvate carboxylase by acetyl-CoA and l-aspartate. Inhibition by AMP is less marked and its physiological role is perhaps limited.

Adenine↗
PubMed1972

The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase and fructose diphosphatase in muscles from vertebrates and invertebrates.

1. The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase and fructose diphosphatase in crude homogenates of vertebrate and invertebrate muscles are reported. 2. Pyruvate carboxylase activity was present in all insect flight muscles that were investigated: in homogenates of bumble-bee flight muscle the activity was inhibited by ADP and activated by acetyl-CoA, and it was distributed mainly in the mitochondrial fraction. This is the first demonstration of pyruvate carboxylase activity in muscle. However, the activity appears to be restricted to insect flight muscle, since it was not found in other invertebrate or vertebrate muscles. 3. Since the three enzymes were never found together in the same muscle, it is concluded that these enzymes cannot provide a pathway for the synthesis of glycogen from lactate or pyruvate in muscle. Other roles for these enzymes in muscle are suggested. In particular, pyruvate carboxylase may be present in insect flight muscle for the provision of oxaloacetate to support the large increase in activity of the tricarboxylic acid cycle which occurs when an insect takes flight.

Acetyl Coenzyme A↗
PubMed1973

Properties and mechanism of action of creatine kinase from ox smooth muscle. Anion effects compared with pyruvate kinase.

1. An improved purification procedure for the brain-type creatine kinase from ox smooth muscle is described. 2. Michaelis constants show the characteristic dependence on the concentration of the second substrate: the derived constants are compared with those for the enzyme from ox brain. 3. Inhibition by iodoacetamide gives a biphasic curve and the total extent of the reaction depends on the enzyme concentration. The rate of inhibition at pH8.6 is not affected by creatine plus MgADP or by a range of simple anions. Addition of creatine plus MgADP plus either NO(3) (-) or Cl(-) ions affords 71.5 and 44% protection respectively. ADP could be replaced by 2-deoxy-ADP but not by alphabeta-methylene ADP, XDP, IDP, GDP or CDP. Nucleotides that did not protect would not act as substrates. 4. Difference-spectra measurements support the interpretation that addition of NO(3) (-) ions to the enzyme-creatine-MgADP complex causes further conformational changes in the enzyme accompanying the formation of a stable quaternary enzyme-creatine-NO(3) (-)-MgADP complex that simulates an intermediate stage in the transphosphorylation reaction. However, the enzyme structure is partially destabilized by quaternary-complex formation. IDP apparently fails to act as a substrate because it cannot induce the necessary conformational change. This behaviour is compared with that of rabbit skeletal muscle creatine kinase. 5. With pyruvate kinase from rabbit muscle, anions activate in the absence of an activating cation and either inhibit or have no effect in its presence. 6. Both activation and inhibition were competitive with respect to the substrate, phosphoenolpyruvate, and curved double-reciprocal plots were obtained. The results may be interpreted in terms of co-operatively induced conformational changes, and this is supported by difference-spectra measurements. However, the Hill coefficient of 1 was not significantly altered. 7. Inhibition by lactate plus pyruvate is less than additive, indicating that both bind to the same site on the enzyme, whereas that by lactate plus NO(3) (-) is additive, indicating binding at separate sites. It is inferred that a quaternary enzyme-pyruvate-NO(3) (-)-MgADP complex could form, but no evidence was obtained to suggest that it possessed special properties comparable with those found with creatine kinase. The implications of these findings for the unidirectional nature of the mechanism of pyruvate kinase is discussed. 8. Lactate or alpha-hydroxybutyrate could not act instead of pyruvate to form a stable quaternary complex, although both activate the K(+)-free enzyme. Only the former inhibits the K(+)-activated enzyme. The activating cation both lowers the Michaelis constant for phosphoenolpyruvate and tightens up the specificity of its binding site.

Adenosine Diphosphate↗
PubMed1977

Diabetes and the control of pyruvate dehydrogenase in rat heart mitochondria by concentration ratios of adenosine triphosphate/adenosine diphosphate, of reduced/oxidized nicotinamide-adenine dinucleotide and of acetyl-coenzyme A/coenzyme A.

1. The proportion of active (dephosphorylated) pyruvate dehydrogenase in rat heart mitochondria was correlated with total concentration ratios of ATP/ADP, NADH/NAD+ and acetyl-CoA/CoA. These metabolites were measured with ATP-dependent and NADH-dependent luciferases. 2. Increase in the concentration ratio of NADH/NAD+ at constant [ATP]/[ADP] and [acetyl-CoA]/[CoA] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between mitochondria incubated with 0.4mM- or 1mM-succinate and mitochondria incubated with 0.4mM-succinate+/-rotenone. 3. Increase in the concentration ratio acetyl-CoA/CoA at constant [ATP]/[ADP] and [NADH][NAD+] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between incubations in 50 micrometer-palmitotoyl-L-carnitine and in 250 micrometer-2-oxoglutarate +50 micrometer-L-malate. 4. These findings are consistent with activation of the pyruvate dehydrogenase kinase reaction by high ratios of [NADH]/[NAD+] and of [acetyl-CoA]/[CoA]. 5. Comparison between mitochondria from hearts of diabetic and non-diabetic rats shows that phosphorylation and inactivation of pyruvate dehydrogenase is enhanced in alloxan-diabetes by some factor other than concentration ratios of ATP/ADP, NADH/NAD+ or acetyl-CoA/CoA.

Acetyl Coenzyme A↗
PubMed1978

Pyruvate-to-ethanol pathway in Entamoeba histolytica.

The pyruvate-to-ethanol pathway in Entamoeba histolytica is unusual when compared with most investigated organisms. Pyruvate decarboxylase (EC 4.1.1.1), a key enzyme for ethanol production, is not found. Pyruvate is converted into acetyl-CoA and CO2 by the enzyme pyruvate synthase (EC 1.2.7.1), which has been demonstrated previously in this parasitic amoeba. Acetyl-CoA is reduced to acetaldehyde and CoA by the enzyme aldehyde dehydrogenase (acylating) (EC 1.2.1.10) at an enzyme activity of 9 units per g of fresh cells with NADH as a reductant. Acetaldehyde is further reduced by either a previously identified NADP+-linked alcohol dehydrogenase or by a newly found NAD+-linked alcohol dehydrogenase at an enzyme activity of 136 units per g of fresh cells. Ethanol is identified as the product of soluble enzymes of amoeba acting on pyruvate or acetyl-CoA. This result is confirmed by radioactive isotopic, spectrophotometric and gas-chromatographic methods.

Acetaldehyde↗
PubMed1978

Pyruvate and ketone-body transport across the mitochondrial membrane. Exchange properties, pH-dependence and mechanism of the carrier.

The effects of exchangeable ions and pH on the efflux of pyruvate from preloaded mitochondria are reported. Efflux obeys first-order kinetics, and the stimulation of efflux by exchangeable ions such as acetoacetate and lactate obeys Michaelis--Menten kinetics. The apparent Km value +/- S.E. for acetoacetate was 0.56 +/- 0.14 mM (n = 5) and that for lactate 12.3 +/- 2.3 mM (n = 6). The Vmax. values +/- S.E. at 0 degrees C were 16.2 +/- 2.0 and 21.9 +/- 2.7 nmol/min per mg of protein. The exchange of a variety of other substituted monocarboxylates was also studied. Efflux was also stimulated by increasing the external pH. The data gave a pK for the transport process of 8.35 and a Vmax. of 3.31 +/- 0.14 nmol/min per mg. The similarity of the Vmax. values for various exchangeable ions but the difference of this from the Vmax. in the absence of exchangeable ions may indicate that transport of pyruvate occurs with H+ and not in exchange for an OH- ion. The inhibition of transport by alpha-cyano-4-hydroxycinnamate took several seconds to reach completion at 0 degrees C. It is proposed that inhibition occurs by binding to the substrate site and subsequent reaction with an -SH group on the inside of the membrane. The inhibitor can be displaced by substrates that can also enter the mitochondria independently of the carrier and so compete with the inhibitor for the substrate-binding site on the inside of the membrane. A mechanism for transport is proposed that invokes a transition state of pyruvate involving addition of an -SH group to the 2-carbon of pyruvate. Evidence is presented that suggests that ketone bodies may cross the mitochondrial membrane either on the carrier or by free diffusion. The physiological involvement of the carrier in ketone-body metabolism is discussed. The role of ketone bodies and pH in the physiological regulation of pyruvate transport is considered.

Animals↗
PubMed1981

Role of pyruvate dehydrogenase and insulin in the regulation of lipogenesis in the lactating mammary gland of the rat during the starved-refed transition.

Administration of insulin with glucose to starved lactating rats, which activates pyruvate dehydrogenase [M. A. Baxter & H. G. Coore (1978) Biochiem. J. 174, 553-561], restored lipogenesis in mammary gland in vivo to 50% of the value observed in refed (2.5 h) rats. The correlations between pyruvate dehydrogenase activity and the rate of lipogenesis persisted in isolated acini. Activation of pyruvate dehydrogenase in vitro with dichloroacetate increased lipogenesis from [6-14C]glucose in acini from starved and refed rats by 250% and 100% respectively. However, in the presence of dichloroacetate, only 70% of the increased flux through pyruvate dehydrogenase was converted into lipid in acini from starved rats, whereas all of the increase could be accounted for as lipid in acini from refed rats. Addition of insulin plus dichloroacetate was required to obtain maximal rates of lipogenesis in acini from starved rats. Similarly, insulin increased the incorporation of [1-14C]acetate into lipid only in acini from starved rats. Although the activity of pyruvate dehydrogenase plays an important role in the control of mammary-gland lipogenesis, the evidence presented suggests a second regulatory site which is insulin-sensitive and is located after the generation of cytosolic acetyl-CoA.

Animals↗
PubMed2003

Insulin stimulation of pyruvate dehydrogenase in adipocytes involves two distinct signalling pathways.

In isolated rat adipocytes, the insulin stimulation of pyruvate dehydrogenase can be partially inhibited by inhibitors of PI3K (phosphoinositide 3-kinase) and MEK1/2 (mitogen-activated protein kinase/extracellular signal-regulated kinase kinase). In combination, U0126 and wortmannin completely block the insulin stimulation of pyruvate dehydrogenase. It is concluded that the effect of insulin on pyruvate dehydrogenase in rat adipocytes involves two distinct signalling pathways: one is sensitive to wortmannin and the other to U0126. The synthetic phosphoinositolglycan PIG41 can activate pyruvate dehydrogenase but the activation is only approx. 30% of the maximal effect of insulin. This modest activation can be completely blocked by wortmannin alone, suggesting that PIG41 acts through only one of the pathways leading to the activation of pyruvate dehydrogenase.

Adipocytes↗
PubMed1982

The induction of synthesis of L-type pyruvate kinase in cultured rat hepatocytes.

Hepatocytes were isolated from preweaned neonatal and adult rats and maintained in primary monolayer culture. Cells from preweaned newborns possessed no L-type pyruvate kinase, nor did they synthesize the enzyme. Incubation for 48-72 h in culture medium supplemented with 2 mM-fructose and 0.1 microM-insulin induced the synthesis of L-type pyruvate kinase, as judged by increased enzyme activity and the increased incorporation of [3H]leucine into immunoprecipitable L-type pyruvate kinase. Hepatocytes isolated from 48 h-starved adult rats incorporated less [3H]leucine into L-type pyruvate kinase than did cells isolated from high-carbohydrate-diet-fed rats. The rate of enzyme synthesis by cells from 48 h-starved rats was increased by the inclusion of fructose and insulin in the incubation medium, after a lag phase of 24-48 h. After 4 days in culture in the presence of fructose and insulin, hepatocytes from 48 h-starved rats synthesized L-type pyruvate kinase at similar rates to hepatocytes isolated from high-carbohydrate-diet-fed rats.

Age Factors↗
PubMed1987

Effects of Ca2+ and Mg2+ on the activity of pyruvate dehydrogenase phosphate phosphatase within toluene-permeabilized mitochondria.

Mitochondria from rat epididymal white adipose tissue were made permeable to small molecules by toluene treatment and were used to investigate the effects of Mg2+ and Ca2+ on the re-activation of pyruvate dehydrogenase phosphate by endogenous phosphatase. Re-activation of fully phosphorylated enzyme after addition of 0.18 mM-Mg2+ showed a marked lag of 5-10 min before a maximum rate of reactivation was achieved. Increasing the Mg2+ concentration to 1.8 mM (near saturating) or the addition of 100 microM-Ca2+ resulted in loss of the lag phase, which was also greatly diminished if pyruvate dehydrogenase was not fully phosphorylated. It is concluded that, within intact mitochondria, phosphatase activity is highly sensitive to the degree of phosphorylation of pyruvate dehydrogenase and that the major effect of Ca2+ may be to overcome the inhibitory effects of sites 2 and 3 on the dephosphorylation of site 1. Apparent K0.5 values for Mg2+ and Ca2+ were determined from the increases in pyruvate dehydrogenase activity observed after 5 min. The K0.5 for Mg2+ was diminished from 0.60 mM at less than 1 nM-Ca2+ to 0.32 mM at 100 microM-Ca2+; at 0.18 mM-Mg2+, the K0.5 for Ca2+ was 0.40 microM. Ca2+ had little or no effect at saturating Mg2+ concentrations. Since effects of Ca2+ are readily observed in intact coupled mitochondria, it follows that Mg2+ concentrations within mitochondria are sub-saturating for pyruvate dehydrogenase phosphate phosphatase and hence less than 0.5 mM.

Animals↗
PubMed1987

Catecholamine activation of pyruvate dehydrogenase in white adipose tissue of the rat in vivo.

Intraperitoneal injections of noradrenaline or adrenaline into rats increased the proportion of pyruvate dehydrogenase in the active state in white adipose tissue; this effect of catecholamines was also apparent in streptozotocin-diabetic rats, showing that it was not due to an increase in serum insulin concentration. The catecholamine-induced increase in pyruvate dehydrogenase of white adipose tissue in vivo was completely blocked by prior injection of either the beta-antagonist propranolol or the alpha 1-antagonist prazosin. Cervical dislocation of conscious rats increased pyruvate dehydrogenase activity of white adipose tissue, which was prevented by prior injection of propranolol. Adrenaline (30 nM) activated pyruvate dehydrogenase in white adipocytes in vitro; the maximum effect of adrenaline required activation of both alpha 1- and beta-receptors. The results show that catecholamines activate pyruvate dehydrogenase of white adipose tissue both in vivo and in vitro and that this effect is mediated by a combination of alpha 1- and beta-adrenergic receptors.

Adipose Tissue↗
PubMed1988

The effects of various anions and cations on the regulation of pyruvate dehydrogenase complex activity from pig kidney cortex.

The activity of pyruvate dehydrogenase complex (PDC) purified from pig kidney cortex was found to be affected by various uni- and bi-valent ions. At a constant strength of 0.13 M at pH 7.8, K+, Na+, Cl-, HCO3- and HPO4(2-) had significant effects on the activity of PDC: Na+, K+ and HPO4(2-) stimulated, but HCO3- and Cl- inhibited. The stimulatory effect of Na+ was mediated by a change in the Vmax. of PDC only, whereas K+ produced an increase in Vmax. and a change in the Hill coefficient (h). The extent of stimulation produced by HPO4(2-)4 on the activity of PDC was dependent on the concentrations of K+ and Na+. Both cations at concentrations higher than 40 mM partially prevented the effect of HPO4(2-)4. Cl- and HCO3- anions decreased the Vmax. of the enzyme and increased the S0.5 for pyruvate. The effects of Na+, K+, Cl-, HPO4(2-) and HCO3- on the activity of PDC were additive. In the presence of 80 mM-K+, 20 mM-Na+, 10 mM-HPO4(2-), 20 mM-Cl- and 20 mM-HCO3- the activity of PDC was increased by 30%, the S0.5 for pyruvate was increased from 75 to 158 microM and h was decreased from 1.3 to 1.1. Under these conditions and at 1.0 mM-pyruvate, the activity of PDC was 80% of the maximal activity achieved in the presence of these ions and 4.5 mM-pyruvate. The present study suggests that PDC may operate under non-saturating concentrations for substrate in vivo.

Animals↗
PubMed1993

Acyloin production from aldehydes in the perfused rat heart: the potential role of pyruvate dehydrogenase.

Aldehydes represent an important class of cytotoxic products derived from free radical-induced lipid peroxidation which may contribute to reperfusion injury following myocardial infarct. Metabolism of aldehydes in the heart has not been well characterized aside from conjugation of unsaturated aldehydes with glutathione. However, aliphatic aldehydes like hexanal do not form stable glutathione conjugates. We have recently demonstrated in vitro that pig heart pyruvate dehydrogenase catalyses a reaction between pyruvate and saturated aldehydes to produce acyloins (3-hydroxyalkan-2-ones). In the present study, rat hearts were perfused with various aldehydes and pyruvate. Acyloins were generated from saturated aldehydes (butanal, hexanal or nonanal), but not from 2-hexanal (an unsaturated aldehyde) or malondialdehyde. Hearts perfused with 2 mM pyruvate and 10-100 microM hexanal rapidly took up hexanal in a dose-related manner (140-850 nmol/min), and released 3-hydroxyoctan-2-one (0.7-30 nmol/min), 2,3-octanediol (0-12 nmol/min) and hexanol (10-200 nmol/min). Small quantities of hexanoic acid (about 10 nmol/min) were also released. The rate of release of acyloin metabolites rose with increased concentration of hexanal, whereas hexanol release attained a plateau when hexanal infusion concentrations rose above 50 microM. Up to 50% of hexanal uptake could be accounted for by metabolite release. Less than 0.5% of hexanal uptake was found to be bound to acid-precipitable macromolecules. When hearts perfused with 50 microM hexanal and 2 mM pyruvate were subjected to a 15 min ischaemic period, the rates of release of 2,3-octanediol, 3-hydroxyoctan-2-one, hexanol and hexanoate during the reperfusion period were not significantly different from those in the pre-ischaemic period. Our results indicate that saturated aldehydes can be metabolically converted by the heart into stable diffusible compounds.

Aldehydes↗