Total Oxidation Rates Research Articles

Mineralization of Organic Matter in Intertidal Sediments of a Tropical Semi-enclosed Delta

Rates and pathways of organic matter decomposition in sediments were examined during winter and summer in two mangrove forests and two accreting mud flats in Hinchinbrook Channel, north-eastern Australia. Rates of O2consumption (range: 2·8–61·0mmolm−2day−1) and CO2release (range: 1·8–21·9mmolm−2day−1) were faster in winter than in summer. Low respiratory quotients (CO2/O2range: 0·24–1·08) and a comparison of other metabolic pathways with total carbon oxidation (Tcox) in summer suggests that most O2was used in oxidizing reduced solutes. Rates of total carbon oxidation were greater in the mangrove sediments than in the mud flats. In winter, sulphate reduction in the mangroves (range: 4·9–8·3mmolSm−2day−1) accounted for a much greater proportion (45–78%) of Tcoxthan in the mud flats where sulphate reduction (range: 0·8–1·0mmolSm−2day−1) was a minor (12–14% of Tcox) metabolic pathway. In summer, sulphate reduction accounted for a greater (62–>100%) proportion of Tcoxin both mangrove (range: 7·9–10·1mmolSm−2day−1) and mud flat (range: 0·8–2·3mmolSm−2day−1) sediments. Rates of denitrification in summer were rapid but highly variable at all four sites (range: 2·9–6·9mmolN2m−2day−1). Rates of Fe and Mn reduction were slow at all four sites (range: 0·0–0·27mmolCm−2day−1) suggesting that metal reduction was a minor decomposition pathway. No methane was detected in the porewater or released from sediments at any of the sites. There was no net microalgal primary production at any of the sites. Mineralization efficiency of organic carbon was low (9–14%) at the most sheltered mud flat, but efficiencies were greater (44–60%) and nearly equivalent at less sheltered mud flat and mangrove habitats, respectively. Imbalances of mineralized carbon between the sum of the various pathways and Tcox, particularly at the mangrove sites, suggest unaccounted losses of dissolved carbon. Large seasonal changes in porewater Cl−concentrations and lack of solute concentration differences with overlying tidal water, imply dilution and tidal advection and/or drainage of interstitial water by intense summer rains.

Oxidation of Methionine Residues in Coagulation Factor VIIa

The oxidation of the activated form of recombinant coagulation factor VII (FVIIa) by hydrogen peroxide has been studied. The three predominant oxidation products observed at pH 7.5 have been characterized as methionine sulfoxide derivatives of the parent protein involving two of the four methionine residues of the protein, Met298 and Met306. We conclude that oxidation of FVIIa with hydrogen peroxide only affects methionine residues and selectively oxidizes those which are readily accessible to the solvent. The oxidation process has been studied in the pH range 3.5–9.5. The total rate of oxidation of FVIIa as well as the formation of the three oxidation products is consistent over the pH interval 7.5–9.5. However, under acidic conditions, significant variations have been observed indicating a conformational change of FVIIa. Oxidized FVIIa had the same amidolytic activity as the native protein. The binding to soluble tissue factor (TF) was weaker after oxidation as manifested by a threefold increase in dissociation constant and the amidolytic activity in complex with soluble TF was 80% compared to that of native FVIIa. In complex with lipid surface TF, the rate of factor X activation catalyzed by oxidized FVIIa was also reduced by approximately 20% compared to that of native FVIIa. However, native and oxidized FVIIa appeared to bind lipidated TF with indistinguishable affinities.

Aqueous phase reactions of mercury with free radicals and chlorine: Implications for atmospheric mercury chemistry

The role of aqueous phase hydroperoxyl radical (HO 2 .), hydroxyl radical ( .OH) and chlorine (HOCl/OCl −) in the redox cycle of atmospheric mercury is investigated. The contributions of the above species to the aqueous phase Hg(II) concentration under various conditions are evaluated by a chemical kinetic model simulating the chemistry in atmospheric droplets. Based on the model results, .OH is an important daytime oxidant for Hg 0 and can account for up to 25 % of the total oxidation rate in the aqueous phase under the model conditions in this study. In the nighttime marine atmosphere, aqueous chlorine can be the most predominant oxidant for Hg 0, contributing up to 90 % of the total oxidation rate in the aqueous phase. Increasing pH from 4.0 to 4.3 and decreasing [Cl −] from 1.0 to 0.5 mM increase [Hg(II)] in the droplets by 50 % and 26 %, respectively. Compared to aqueous SO 2, HO 2 . can reduce Hg(II) at a significant rate. In addition, HO 2 . is the only reductant balancing all the oxidation processes of Hg 0 after SO 2 is depleted.

Contribution of mitochondria and peroxisomes to palmitate oxidation in rat and bovine tissues

Total and peroxisomal palmitate oxidation capacities and mitochondrial enzyme activities were compared in tissues from growing rats, preruminant calves and 15-month-old bulls. Total palmitate oxidation rates were 1.9–5.2-fold higher in rat than in bovine tissues and 1.7-fold higher in the heart and muscles from calves than from growing bulls. The peroxisomal contribution to palmitate oxidation was similar between rats and bovines (i.e. calves and bulls) in liver (35–51%), heart (26%) but not in muscles (14±3% in rats vs 33±4.5% in bovines, P<0.05). Mitochondrial enzyme activities were 1.8–4.8-fold higher in rat than in bovine tissues but the citrate synthase to cytochrome- c oxidase ratio was the highest in the liver (17–38), intermediate in the heart and muscles from calves and rats (6–10) and the lowest in heart and muscles from bulls (2–3, P<0.05). In all tissues and animal groups, palmitate oxidation rates were similar per unit cytochrome- c oxidase activity, but not always per unit citrate synthase activity. Therefore, differences in mitochondrial contents (as between rats and bovines) or in mitochondrial characteristics (as between liver and muscles) relate to the differences in palmitate oxidation capacity.

Effect of a carbohydrate-electrolyte drink on endurance capacity during prolonged intermittent high intensity running.

OBJECTIVE: To examine the effect of a carbohydrate-electrolyte solution on endurance capacity during prolonged intermittent running. METHODS: Nine subjects (eight men and one woman) ran to exhaustion on a motorised...

Oxidation in Traditional Mediterranean Meat Products

Lipid oxidation in dry-fermented sausages and dry-salted-hams, representative items of traditional Mediterranean pork products, is responsible for the production of compounds which can affect their organoleptic qualities and wholesomeness. Lipid-derived compounds make up an important share of the volatiles extracted from matured products, once the contribution of spices is removed, and contribute significantly to the flavour of old style products. The few reports available on oxysterols depict a total cholesterol oxidation rate of about 0.1%, a threshold level for toxic effects to occurin vitro but about 100 times lower of thein vivo toxicity dose. The value could perhaps be reduced with the use of antioxidants. Phospholipids are the main class of fats interested by lipolysis and unsaturated fatty acids are those most interested by oxidation. On that basis, the case of special feeding regimes, such as that of Iberian pigs, and the possible relevance of muscle fibre type on flavour development are discussed.

Oxidation in traditional mediterranean meat products

Lipid oxidation in dry-fermented sausages and dry-salted-hams, representative items of traditional Mediterranean pork products, is responsible for the production of compounds which can affect their organoleptic qualities and wholesomeness. Lipid-derived compounds make up an important share of the volatiles extracted from matured products, once the contribution of spices is removed, and contribute significantly to the flavour of old style products. The few reports available on oxysterols depict a total cholesterol oxidation rate of about 0.1%, a threshold level for toxic effects to occur in vitro but about 100 times lower of the in vivo toxicity dose. The value could perhaps be reduced with the use of antioxidants. Phospholipids are the main class of fats interested by lipolysis and unsaturated fatty acids are those most interested by oxidation. On that basis, the case of special feeding regimes, such as that of Iberian pigs, and the possible relevance of muscle fibre type on flavour development are discussed.

Wet oxidation as a pretreatment method for wastewaters contaminated by bioresistant organics

The partial wet air oxidation of aqueous solutions of polyethylene glycol, a model organic pollutant typically found in wastewaters of polymer-manufacturing, has been investigated at temperatures from 383 K to 513 K and oxygen partial pressures from 2 MPa to 3 MPa. The progress of the reaction was investigated in terms of COD and TOC removal, while fragmentation of the original polymer to lower molecular weight compounds was followed by means of liquid chromatography. The impact of various heterogeneous and homogeneous catalysts on the kinetics and mechanisms of the reaction has also been studied. Conversion of the model compound through various oxidation intermediates to end-products, such as carboxylic acids and oligomers, could be easily achieved even under mild operating conditions, while further total oxidation proved to be difficult even under more severe conditions. Catalysts were found to be, in general, capable of increasing the rates of total uncatalysed oxidation. The implications for complete removal of bioresistant organic pollutants by partial wet oxidation followed by a biological treatment step are also discussed.

Purification and characterization of three constitutive cytochrome P-450 isoforms from bovine olfactory epithelium.

Three constitutive forms of cytochrome P-450 (P-450s) were isolated from olfactory microsomes of cattle. The purified P-450s, designated P-450bov1, P-450bov2 and P-450bov3, were electrophoretically nearly homogeneous by SDS/PAGE and their apparent relative molecular masses were estimated to be 50000, 53000 and 51000 respectively. As indicated by several criteria including the N-terminal sequence and absorption spectra, the three olfactory forms of P-450 were distinct from each other and from all the other P-450s currently known in cattle. P-450bov1 and P-450bov2 were purified in the low-spin state, whereas P-450bov3 was in the high-spin state. Studies to evaluate, by Western blot analysis, the reactivity of these purified P-450s with antibodies raised against rat hepatic P-450 2E1, 2B, 1A and 3A and rabbit olfactory P-450NMa and P-450NMb showed that P-450bov3 strongly cross-reacted with anti-P-450NMb IgG, and P-450bov1 moderately with anti-P-450NMa IgG. As determined by immunoblots, P-450bov1 and P-450bov3 represented a great portion of the total olfactory P-450. In a reconstituted system with NADPH:cytochrome P-450 reductase and phospholipids, P-450bov1 was more active in the metabolism of xenobiotic compounds (i.e. O-de-ethylation of ethoxycoumarin and N-demethylation of hexamethylphosphoramide) than towards endogenous substrates (testosterone and progesterone). Conversely, P-450bov3 metabolized the xenobiotics at lower rates but exhibited total oxidation rates of the above sex hormones higher than those of P-450bov1. From the comparison of the catalytic, immunochemical and structural properties, it was inferred that P-450bov1 and P-450bov3 are the bovine orthologues of P-450NMa (2A) and P-450NMb (2G1) respectively, the only two olfactory P-450s previously purified from rabbit. P-450bov2, which showed low activity toward some exogenous and endogenous compounds, represents a novel purified olfactory hemoprotein possibly belonging to the 3A subfamily. These results are consistent with a specific presence of catalytically and structurally similar P-450s, at least for the major ones, in the olfactory mucosa of mammals.

Reaction mechanisms and kinetics of chemical pretreatment of bioresistant organic molecules by wet air oxidation

The partial wet air oxidation of aqueous solutions of p-coumaric acid and polyethylene glycol, two model organic pollutants typically found in wastewaters of agricultural origin and polymer-manufacturing respectively, has been investigated at temperatures from 373 K to 513 K and oxygen partial pressures from 0.2 MPa to 3 MPa. Reaction intermediates have been identified and their concentration profiles have been determined using liquid chromatography as the main analytical technique, and reaction mechanisms and pathways have been postulated. The impact of various heterogeneous catalysts, such as metal oxides and noble metals, on the kinetics and mechanisms of the reaction has also been studied. Conversion of these model compounds through various oxidation intermediates to end-products, such as carboxylic acids, could be easily achieved even under mild operating conditions, while further total oxidation proved to be difficult even under more severe conditions. Catalysts were found to be, in general, capable of increasing the rates of both partial and total uncatalysed oxidation. The stability of some of the catalysts used has also been studied with respect to metal leaching and deactivation. The implications for complete removal of bioresistant organic pollutants by partial wet oxidation followed by a biological treatment step are also discussed.

Reaction mechanisms and kinetics of chemical pretreatment of bioresistant organic molecules by wet air oxidation

The partial wet air oxidation of aqueous solutions of p-coumaric acid and polyethylene glycol, two model organic pollutants typically found in wastewaters of agricultural origin and polymer-manufacturing respectively, has been investigated at temperatures from 373 K to 513 K and oxygen partial pressures from 0.2 MPa to 3 MPa. Reaction intermediates have been identified and their concentration profiles have been determined using liquid chromatography as the main analytical technique, and reaction mechanisms and pathways have been postulated. The impact of various heterogeneous catalysts, such as metal oxides and noble metals, on the kinetics and mechanisms of the reaction has also been studied. Conversion of these model compounds through various oxidation intermediates to end-products, such as carboxylic acids, could be easily achieved even under mild operating conditions, while further total oxidation proved to be difficult even under more severe conditions. Catalysts were found to be, in general, capable of increasing the rates of both partial and total uncatalysed oxidation. The stability of some of the catalysts used has also been studied with respect to metal leaching and deactivation. The implications for complete removal of bioresistant organic pollutants by partial wet oxidation followed by a biological treatment step are also discussed.

Wet oxidation as a pretreatment method for wastewaters contaminated by bioresistant organics

The partial wet air oxidation of aqueous solutions of polyethylene glycol, a model organic pollutant typically found in wastewaters of polymer-manufacturing, has been investigated at temperatures from 383 K to 513 K and oxygen partial pressures from 2 MPa to 3 MPa. The progress of the reaction was investigated in terms of COD and TOC removal, while fragmentation of the original polymer to lower molecular weight compounds was followed by means of liquid chromatography. The impact of various heterogeneous and homogeneous catalysts on the kinetics and mechanisms of the reaction has also been studied. Conversion of the model compound through various oxidation intermediates to end-products, such as carboxylic acids and oligomers, could be easily achieved even under mild operating conditions, while further total oxidation proved to be difficult even under more severe conditions. Catalysts were found to be, in general, capable of increasing the rates of total uncatalysed oxidation. The implications for complete removal of bioresistant organic pollutants by partial wet oxidation followed by a biological treatment step are also discussed.

Catalytic wet air oxidation of polyethylene glycol

The catalytic oxidation of aqueous solutions of polyethylene glycol of molecular weight 10000, a synthetic polymer used in a wide range of applications, has been investigated using various metal oxide and noble metal heterogeneous catalysts. Catalysts were in slurry or in pellets, at temperatures from 383 K to 463 K and an oxygen partial pressure of 3 MPa. Additional uncatalysed experiments have been performed, and the results are compared to those of the catalysed runs. Reaction intermediates have been determined using HPLC and gel permeation chromatography as the main analytical techniques, and reaction mechanisms have been proposed. Noble metal catalysts were found to be more effective than metal oxide catalysts for oxidising polyethylene glycol, while with both noble metal and metal oxide catalysts the rate of total oxidation was significantly higher than that of the uncatalysed reaction. However, the use of heterogeneous catalysts was found to be responsible for prolonged induction periods, a phenomenon which did not occur significantly during the uncatalysed runs. A palladium supported on alumina catalyst was further studied with respect to its stability and deactivation.

Impact of surface mobility in selective oxidation. Isotopic exchange of 18O 2 with 16O 2 on various oxides: MoO 3, SnO 2 and Sb 2O 4. Effect of a reducer gas

Isotopic oxygen exchange experiments were carried out on simple oxides (Sb 2O 4, MoO 3 and SnO 2) and mechanical mixtures of MoO 3 or SnO 2(acceptor phase) with Rh//Al 2O 3 or Sb 2O 4 (donor phase). With Rh//Al 2O 3 a synergy effect is found: the amount of oxygen exchanged on the mixture is higher than the sum of oxygen exchanged on the two separate phases. This is a prove of oxygen mobility between donor and acceptor phases. With Sb 2O 4 this effect is less marked suggesting that the presence of a reducer gas is required. In presence of hydrocarbon, no isotopic exchange is observed: only total oxidation occurs. The presence of Sb 2O 4 decreases the rate of total oxidation by blocking, by oxygen spillover, the most active sites for oxidation.

A multicomponent reactive transport model of early diagenesis: Application to redox cycling in coastal marine sediments

STEADYSED1 is a multicomponent reactive transport code for steady-state early diagenesis which fully incorporates the reaction couplings among the elements, C, O, N, S, Fe, and Mn. The model is tested against extensive datasets collected by Canfield et al. (1993a,b) at three coastal marine sites that exhibit high rates of combined iron and manganese (hydr)oxide reduction. It is shown that the model provides a consistent explanation of the entire body of multicomponent multisite observations. The measured concentration profiles of twenty-eight individual porewater and solid sediment species are satisfactorily reproduced. Furthermore, the model predicts the observed distributions of sulfate reduction rates, as well as diagnostic features of the porewater pH profiles. The coupled nature of the reactive species imposes stringent constraints when fitting model-calculated distributions to the data, because a single set of reaction and transport parameters must account for the profiles of all the species at each site. The parameters are further separated into site-specific (e.g., deposition fluxes, bottom water composition) and reaction-specific parameters (e.g., rate coefficients, apparent equilibrium constants, limiting substrate concentrations). By minimizing the variations of the reaction-specific parameters from one site to another, the fitting strategy emphasizes the retrieval from field data of reaction parameters that are mechanistically meaningful. The model reproduces the significant vertical overlap between organic carbon oxidation pathways observed in the sediments. The overlap is explained by the combination of high rates of organic carbon oxidation plus intense bioturbation and irrigation at the sites studied. The model-derived contributions of the various respiratory processes compare favorably with the incubation results of Canfield et al. (1993a,b). Aerobic respiration accounts for less than 32% of total organic carbon oxidation at the three sites. From 22 to 46% of the O 2 uptake by the sediments is directly coupled to organic carbon oxidation, while the remainder is used for the oxidation of secondary reduced species, in particular dissolved, adsorbed and solid Fe(II) and Mn(II) species. According to the model, the oxidation of Fe 2+ by Mn (hydr)oxides is responsible for the observed spatial separation of the porewater build-up of Mn 2+ and Fe 2+. At two of the sites, 75 and 97% of the total rate of Mn oxide reduction is due to chemical reaction with dissolved Fe 2+. In contrast, at the same sites, iron (hydr)oxides are mostly utilized by bacteria for the oxidation of organic matter (dissimilatory iron reduction). As shown also by Canfield et al. (1993a,b), dissimilatory reduction is the principal dissolution pathway for manganese oxides at the third site. A sensitivity analysis suggests that, for given deposition fluxes of reactive Fe and Mn, the competition between dissimilatory and nondissimilatory metal reduction pathways depends primarily on the total carbon oxidation rate and the intensity of porewater irrigation. The simulations also highlight the importance of adsorption-desorption of Fe(II) and Mn(II) in the redox cycling of the metals, as well as their impact on porewater alkalinity and pH. Based on the calculated rate distributions, detailed budgets of Fe, Mn, and O 2 in the sediments are presented. The model-calculated benthic exchange fluxes of solutes are dominated by irrigation. For nitrate, molecular diffusion and irrigation cause fluxes in opposite directions. As a result, there is a net transfer of nitrate from the water column to the sediments, although the interfacial porewater gradients predict diffusional fluxes out of the sediments. A significant fraction of the benthic Fe and Mn fluxes to the bottom waters may be due to desorption at the water-sediment interface.

Effects of Acute and Chronic Exercise on Fat Metabolism

Fatty acids are an important source of energy for skeletal muscle contraction, particularly during exercise of mild-moderate intensity, prolonged duration, and in the fasting state. Plasma FFA transported from remote adipose tissue stores and triglycerides contained within skeletal muscle fibers are the major sources of these fatty acids. The relative contribution of each source is dependent on the mode, intensity, and duration of exercise and on training status. Plasma FFA oxidation is directly related to the rate of lipolysis in adiopose tissue. The most potent stimulants of the latter are the catecholamines, but a lower plasma insulin concentration during exercise also plays a contributory role. In contrast, intramuscular triglyceride hydrolysis appears to be mediated entirely by beta 2-adrenergic stimulation. Endurance training substantially enhances fatty acid oxidative capacity in skeletal muscle and increases the proportion of energy derived from fatty acid oxidation during exercise. In addition, the sympathoadrenal response to exercise is markedly blunted in the trained state. Studies conducted in our laboratory indicate that plasma FFA and glycerol concentrations and whole body FFA uptake and oxidation are all decreased during moderate-intensity exercise at the same absolute work rate after physical conditioning, probably because of the reduction of sympathoadrenal activity. However, the lipolytic response to catecholamines also is enhanced in trained subjects. Perhaps as a consequence, the magnitude of the decrease in lipolysis and plasma FFA oxidation is less than the decrement in sympathoadrenal activity in the same individuals during exercise in the trained state. Other investigations were conducted in our laboratory to determine the source of the additional fatty acids oxidized in physically conditioned subjects. These studies demonstrated that during moderate-intensity exercise at the same absolute work rate, depletion of triglycerides from within skeletal muscle fibers was twice as great after, as opposed to, before training. Regardless of training status, intramuscular triglyceride use accounted for about 90% of the oxidized fatty acids that were not supplied from adipose tissue via the plasma. Intramuscular triglycerides were the source of virtually all of the additional fatty acids oxidized in the trained state. Both before and after physical conditioning they explained the discrepancy between the rates of plasma FFA and total fat oxidation during moderate-intensity exercise of up to 2 hr in duration.

Effect of parenteral amino acids on leucine and urea kinetics in preterm infants

OBJECTIVE: To examine the effect of two commonly used parenteral alimentation amino acid mixtures on whole-body leucine and urea kinetics. METHODS: Ten stable preterm infants were studied during the first 4 weeks after birth. Six infants received a mixture containing higher branched-chain amino acids, lower glycine plus added dicarboxylic acids formulation (Trophamine), and four received a standard amino acid mixture (Aminosyn). Whole-body protein turnover was measured with [1- 13C]leucine tracer, and the rate of oxidation of protein was calculated by quantifying the appearance of carbon 13 from leucine in carbon dioxide as well as from rates of urea synthesis estimated by using [ 15N 2]urea tracer. Energy consumption and substrate oxidation were quantified by indirect respiratory calorimetry. Infants were given similar quantities of energy (≈61 kcal/kg per day), glucose (≈10.7 mg/kg per minute) and protein (≈2.1 gm/kg per day). RESULTS: There was no significant difference in the rate of appearance of leucine in the two groups. However, the fraction of leucine oxidized ( p = 0.002) and total rate of oxidation of leucine was higher in the Trophamine group. Thus additional branched-chain amino acids resulted in an increased contribution of C-1 of leucine to expired CO 2. The rate of urea N synthesis was also similar in the two groups (Trophamine: 2.92 ± 0.87 mg N/kg per hour; Aminosyn: 2.70 ± 1.18 mg N/kg per hour). CONCLUSIONS: Although the use of Trophamine normalizes the blood amino acid pattern, it does not appear to improve nitrogen/protein kinetics. Furthermore, the additional branched-chain amino acids are disposed of by increased oxidation. (J P EDIATR 1996;128:130-4)

CO Oxidation over Rh Dispersed on SiO2, Al2O3 and TiO2: Kinetic Study and Oscillatory Behavior

The kinetic behavior of Rh supported on SiO2, Al2O3, and TiO2 in the CO oxidation reaction has been investigated. It was found that the maximum turnover frequency (TOF) is approximately the same over the three catalysts, although the maximum is shifted to lower CO pressures for Rh/Al2O3 and Rh/TiO2 than for Rh/SiO2 catalyst. At high CO pressures, a change from −1. to −0.4 in the reaction order with respect to CO was observed over Rh/Al2O3, while in the case of Rh/TiO2 a similar change from −1 to −0.2 was observed. These changes are attributed to the contribution of the CO dissociation step to the total oxidation rate. Oscillatory behavior and hysteresis were observed on all catalysts at 393 K. However, the window of oscillation with respect to the CO pressure was much wider on Rh/SiO2 than on the other catalysts. On-line mass spectrometry was used to follow the precise oscillatory patterns as a function of reaction temperature over the Rh/SiO2 catalyst. The oxidation/reduction of the rhodium surface is proposed to be the dominant mechanism responsible for the observed oscillatory behavior.

Effects of branched-chain amino acid infusion on protein metabolism in rats with acute hepatic failure

Branched-chain amino acids (BCAA) are known to improve hepatic encephalopathy as well as protein malnutrition in cirrhosis. However, such effects in acute hepatic failure (AHF) remain to be elucidated. The current study was conducted to investigate whether BCAA improves protein metabolism in AHF. AHF was induced in male Donryu rats weighing approximately 230 g by giving 60 mg/kg lipopolysaccaride intravenously and 800 mg/kg D-galactosamine hydrochloride intraperitoneally. From 18 hours after injection, AHF rats and control rats were given one of the following five solutions intravenously for 6 hours: 1) saline, 2) 10% glucose, 3) standard 10% amino acid formula with total nitrogen content of 12.2 g/L and BCAA/aromatic amino acid molar ratio of 37.05, 4) BCAA-enriched solution with nitrogen content of 21.9 g/L and the ratio of 148.2, or 5) an active placebo against BCAA-enriched solution with nitrogen content of 21.9 g/L and the ratio of 37.05. In parallel, each group was given a continuous infusion of 14C-leucine. After the plasma radioactivity of 14C-leucine and the expired 14CO 2 level reached a plateau, protein turnover was analyzed according to the kinetic model proposed previously by Waterlow. When compared with the control, rates of total protein turnover (total flux), oxidation, and breakdown all increased significantly in AHF. Infusion of standard 10% amino acid formula, BCAA-enriched solution or the placebo in AHF increased total flux and oxidation significantly as compared with the effect of saline or 10% glucose. Although saline, 10% glucose, standard 10% amino acid formula, and the placebo had no effect on synthesis rate, it was increased significantly with BCAA-enriched solution. Breakdown was not suppressed with any solution. These results suggest that rats with AHF are in a catabolic state and that any of the three amino acid solutions can be oxidized to provide energy in AHF. In addition, infusion of BCAA-enriched solution may have a specific protein-sparing effect by increasing the protein synthesis rate even with liver damage. Hence, it is conceivable that infusion of BCAA improves protein metabolism in AHF.

Effects of branched-chain amino acid infusion on protein metabolism in rats with acute hepatic failure

Branched-chain amino acids (BCAA) are known to improve hepatic encephalopathy as well as protein malnutrition in cirrhosis. However, such effects in acute hepatic failure (AHF) remain to be elucidated. The current study was conducted to investigate whether BCAA improves protein metabolism in AHF. AHF was induced in male Donryu rats weighing approximately 230 g by giving 60 mg/kg lipopolysaccaride intravenously and 800 mg/kg D-galactosamine hydrochloride intraperitoneally. From 18 hours after injection, AHF rats and control rats were given one of the following five solutions intravenously for 6 hours: 1) saline, 2) 10% glucose, 3) standard 10% amino acid formula with total nitrogen content of 12.2 g/L and BCAA/aromatic amino acid molar ratio of 37.05, 4) BCAA-enriched solution with nitrogen content of 21.9 g/L and the ratio of 148.2, or 5) an active placebo against BCAA-enriched solution with nitrogen content of 21.9 g/L and the ratio of 37.05. In parallel, each group was given a continuous infusion of 14C-leucine. After the plasma radioactivity of 14C-leucine and the expired 14CO2 level reached a plateau, protein turnover was analyzed according to the kinetic model proposed previously by Waterlow. When compared with the control, rates of total protein turnover (total flux), oxidation, and breakdown all increased significantly in AHF. Infusion of standard 10% amino acid formula, BCAA-enriched solution or the placebo in AHF increased total flux and oxidation significantly as compared with the effect of saline or 10% glucose. Although saline, 10% glucose, standard 10% amino acid formula, and the placebo had no effect on synthesis rate, it was increased significantly with BCAA-enriched solution.(ABSTRACT TRUNCATED AT 250 WORDS)