Cardiac protein degradation in acute overload in vitro: reutilization of amino acids

Cardiac Myosin Filaments are Maintained by Stochastic Protein Replacement

Myosin and myosin-binding protein C are exquisitely organized into giant filamentous macromolecular complexes within cardiac muscle sarcomeres, yet these proteins must be continually replaced to maintain contractile fidelity. The overall hypothesis that myosin filament structure is dynamic and allows for the stochastic replacement of individual components was tested in vivo, using a combination of mass spectrometry- and fluorescence-based proteomic techniques. Adult mice were fed a diet that marked all newly synthesized proteins with a stable isotope-labeled amino acid. The abundance of unlabeled and labeled proteins was quantified by high-resolution mass spectrometry over an 8-week period. The rates of change in the abundance of these proteins were well described by analytical models in which protein synthesis defined stoichiometry and protein degradation was governed by the stochastic selection of individual molecules. To test whether the whole myosin filaments or the individual components were selected for replacement, cardiac muscle was chemically skinned to remove the cellular membrane and myosin filaments were solubilized with ionic solutions. The composition of the filamentous and soluble fractions was quantified by mass spectrometry, and filament depolymerization was visualized by real-time fluorescence microscopy. Myosin molecules were preferentially extracted from ends of the filaments in the presence of the ionic solutions, and there was only a slight bias in the abundance of unlabeled molecules toward the innermost region on the myosin filaments. These data demonstrate for the first time that the newly synthesized myosin and myosin-binding protein C molecules are randomly mixed into preexisting thick filaments in vivo and the rate of mixing may not be equivalent along the length of the thick filament. These data collectively support a new model of cardiac myosin filament structure, with the filaments being dynamic macromolecular assemblies that allow for replacement of their components, rather than rigid bodies.

An Exploratory Study of Cognitive Involvement in Hereditary Transthyretin Amyloidosis

OBJECTIVES

Hereditary amyloidogenic transthyretin (ATTRv) amyloidosis is an autosomal dominant disorder caused by mutations of the transthyretin (TTR) gene. The mutant ATTRv protein causes a systemic accumulation of amyloid fibrils in various organs. TTR is an important protein in the central nervous system physiology for the maintenance of normal cognitive process during aging, amidated neuropeptide processing, and nerve regeneration. The neuroprotective effect of transthyretin has been widely documented in animal models. Cognitive consequences of the mutant TTR in hereditary ATTRv amyloidosis patients remain still to be elucidated. We designed this study to investigate the cognitive involvement in ATTRv amyloidosis.

METHODS

Detailed neuropsychological tests and cranial MRIs were performed. Biomarkers including amyloid beta 1-42, total tau, and phosphorylated tau were investigated in the cerebrospinal fluid samples.

RESULTS

Median age of the cohort was 52 years (ranges 34-72). Neuropsychological assessment results were compatible with impaired executive functions (in all patients except one with only bilateral carpal tunnel syndrome, long-term visual and long-term verbal memory (severe in four patients and moderate in one). Visuospatial judgment and perception were impaired in six. Mean cerebrospinal fluid Aβ1-42 (pg/ml) was 878.0 ± 249.5 in patients with cortical atrophyin MRI whereas 1210.0 ± 45.9 in patients without any cortical atrophy. Cranial MRI showed cortical atrophy in six patients (6/10).

CONCLUSION

Our data showed the significance of the TTR protein in cognitive functions and highlighted the importance of the close follow-up of cognitive functions in ATTRv amyloidosis patients.

Effect of taurine on the proteomic profile of the cytosolic and microsomal fractions of rat hepatocytes during ontogeny

The proteomic features of the cytosolic and microsomal fractions of rat hepatocytes were studied during long-term dietary consumption of taurine (12 months) as a modulator of energy homeostasis. We identified proteomic markers of the effect of taurine on regulation of cell homeostasis. A protein with unknown biological function was revealed.

Transthyretin and Alzheimer's disease: where in the brain?

Transthyretin (TTR), a carrier protein for thyroxine and retinol in plasma and cerebrospinal fluid (CSF), has been shown to bind the amyloid beta peptide. Accordingly, TTR has been suggested to protect against amyloid beta deposition, a key pathological feature in Alzheimer's disease (AD). Supporting this view are the reduced TTR levels found in CSF of patients with AD, as well as reports of altered TTR expression in the cortex and hippocampus of AD rodent models. Importantly, early characterization of TTR distribution revealed the choroid plexus as the site of TTR synthesis within the brain. To resolve this controversy we used precise laser microdissection technology to assay for TTR mRNA expression. Our results clearly demonstrate that TTR is not produced in the brain parenchyma of wild-type mice nor in two different transgenic mouse models of AD, suggesting that contamination by choroid plexus contributed to the recent results indicating TTR production in various brain regions. The relevance of TTR to AD should now take into consideration TTR production by the choroid plexus and its ability, in the CSF, to sequester the amyloid beta peptide.

Load responsiveness of protein synthesis in adult mammalian myocardium: role of cardiac deformation linked to sodium influx

Exposure of adult mammalian myocardium to increased hemodynamic loads augments cardiac protein synthesis, ultimately leading to hypertrophy of the affected chamber. This established relationship between loading conditions and protein synthesis was examined in terms of two questions. First, is there a basic difference between the anabolic effect of a passive load imposed on diastolic myocardium and that of an active load generated by systolic myocardium? This issue was addressed by measuring [3H]phenylalanine incorporation into muscle protein in either quiescent or contracting ferret papillary muscles, set at known isometric lengths. Myocardial protein synthesis increased in proportion to total muscle tension in each case, with an equivalent relation describing both quiescent and contracting muscles. Synthesis of two contractile proteins, actin and myosin heavy chain, were enhanced by muscle loading. Thus, a quantitative rather than qualitative difference between the anabolic effects of diastolic and systolic loading was demonstrated. Second, since increased sodium influx is an initial cellular response requisite to the growth-inducing activity of many substances, and since sodium entry through stretch-activated ion channels is stimulated by deformation of the sarcolemma, does cardiac deformation during increased loading promote sodium influx as a signal to increase anabolic activity? In either quiescent or contracting papillary muscles, the rate of 24Na+ uptake was found to increase with load. Streptomycin, a cationic blocker of the mechanotransducer ion channels, was without effect on protein synthesis in stimulated but slack muscles; however, it inhibited, in a dose-related manner, the augmented protein synthesis otherwise observed in contracting muscles developing tension. At 500 microM, streptomycin did not reduce active tension, but it did reduce the synthesis of both actin and myosin heavy chain. In a second pharmacologic approach, inotropic agents were chosen which uniformly increased muscle tension development but which had contrasting effects on sodium influx. Protein synthesis increased in the presence of Na+ influx enhancers, monensin or veratridine; however, protein synthesis decreased in the presence of amiloride, a sodium influx inhibitor. Thus, myocardial protein synthesis varied directly with sodium influx despite the positive inotropic effect observed with each of these agents. In addition, inhibition of protein synthesis by ouabain demonstrated that activation of the Na+ pump is required for the anabolic effect of load.(ABSTRACT TRUNCATED AT 400 WORDS)

Aortic pressure as a determinant of cardiac protein degradation

Mechanical parameters and intracellular mediators that may control protein degradation were studied in isolated rat hearts subjected to increased aortic pressure. Elevation of aortic pressure from 60 to 120 mmHg in Langendorff preparations provided glucose or pyruvate as substrate decreased the rate of protein degradation during the second hour of perfusion. Intracellular contents of ATP or creatine phosphate or the creatine phosphate/creatine ratio did not indicate that energy depletion accounted for these effects. When ventricular pressure development was prevented by ventricular draining, and hearts were arrested with tetrodotoxin, protein degradation still decreased as aortic pressure was raised. The effect of elevated aortic pressure on proteolysis was unchanged when perfusate calcium concentrations were 0.6, 3.0, or 5.1 mM, or when indomethacin or meclofenamate was added to the perfusion buffer. These results provided no evidence to indicate that intraventricular pressure development or cardiac contraction was responsible for the inhibitory effect of increased aortic pressure on protein degradation. Instead, they suggested that stretch of the ventricular wall, as a consequence of increased aortic pressure, could be the mechanical parameter most closely related to the restraint on proteolysis. No evidence was obtained that the lower rate of degradation depended on energy or calcium availability or prostaglandin synthesis.

Intracellular turnover and cardiac hypertrophy

Ultrastructural evidence is presented that intracellular autophagic degradation of cytoplasmic constituents is reduced during pressure induced hypertrophy of left ventricular myocardium after supravalvular aortic constriction in rats. This anti-catabolic reaction has to be considered as an important mechanism for shifting the balance between synthesis and degradation to the positive side. Short term studies after administration of isoproterenol suggest a close functional relationship between work load on the one hand and the anti-catabolic reaction on the other.

Simultaneous response of myocardial contractility and a major proteolytic process to beta-adrenergic-receptor occupancy in the Langendorff isolated perfused rat heart

The Langendorff isolated rat heart was adapted to the study of minute-to-minute percentage changes in bulk protein degradation by using non-recirculating perfusion. Hearts were perfused at 8 ml/min at 35 degrees C with Krebs-Henseleit buffer containing 11 mM-glucose, and only hearts with regular ventricular rhythm were employed. Proteins were labelled by infusion of [3H]leucine for 0.5 h in vitro. A complete amino acid mixture was then added at 3 times normal rat extracellular concentrations. After labelling, the re-incorporation of [3H]leucine was competitively inhibited by addition of either 4 mM-leucine or 20 microM-cycloheximide. The residual unincorporated radioactivity and the preferentially labelled rapid-turnover proteins were eliminated during a 3 h preliminary perfusion period. The basal rate of release of [3H]leucine and percentage changes were then determined at 1 min intervals, by using each heart as its own control. Leucine metabolism was inconsequential to results. Exchange of intracellular leucine pools with extracellular leucine and subsequent release in effluent perfusate was 95% complete within approx. 2 min. The basal rate of protein degradation was unchanged by electrical stimulation of the heart rate to 360 beats/min or cessation of contractile activity by membrane depolarization under 25 mM-KCl. Infusion of the beta-agonist isoprenaline at 5-500 nM caused a graded inhibition of myocardial protein degradation within 5-6 min, with a maximum inhibition of 30%. This inhibition was sustained for at least 1 h of drug administration and was reversed within 4-6 min of cessation of isoprenaline or simultaneous infusion of 1 microM of the beta-receptor antagonist propranolol. Minute-to-minute adrenergic proteolytic control was a simultaneous co-variable with beta-receptor-mediated inotropic changes in right-intraventricular systolic pressure. Stoppage of the heart in asystole by the Ca2+-channel blocker nifedipine (0.7 microM) delayed the onset, but did not cause sustained reversal, of adrenergic-inhibited degradation, indicating the absence of a direct obligatory mechanistic linkage between the events of the contraction-relaxation cycle and protein degradation in this preparation.

Ethanol and cardiac protein synthesis

Acute exposure of the heart to ethanol does not appear to alter the rate of young guinea pig cardiac protein synthesis when assayed in vitro. In contrast, the primary metabolite of ethanol, acetaldehyde, markedly diminishes synthesis despite its chronotropic and inotropic effects. On the other hand, after 11-13 weeks of ethanol-drinking during growth and maturation, the synthetic capacity of the working right ventricle was decreased when measured in vitro with normal perfusate. Assay of synthesis of the contractile proteins myosin heavy and light chains, actin and tropomyosin suggests a change in synthesis or pool size of actin reflected in an alteration of relative synthesis of this protein compared to that of heavy chains. The relative synthesis of the other proteins remained at control levels. When hearts from ethanol-drinking and matched control animals were perfused under conditions of severe ischemia, there was a profound fall in protein synthesis in all hearts, and ethanol did not enhance the inhibition of synthesis. However, the hearts from ethanol-drinking animals showed a more marked and significant impairment of maintaining ejection pressure with a marked increase in coronary resistance as the perfusion progressed. It is postulated that some impairment of protein metabolism may occur during prolonged ethanol exposure, which may influence the cardiac response of another induced stress, e.g., ischemia.

Cardiac hypertrophy in rats after supravalvular aortic constriction. II. Inhibition of cellular autophagy in hypertrophying cardiomyocytes

Adult male Sprague-Dawley rats were killed by retrograde perfusion fixation 3, 7, 14, 21 and 35 days after supravalvular aortic constriction (n = 33) or sham-operation (n = 25). Subepicardial specimens of the left ventricular myocardium were evaluated by conventional electron microscopic morphometry, and in addition were examined for the occurrence of autophagic vacuoles (AVs) using large test areas (3.9 X 10(4) micron 2 per animal). The quotient of mitochondrial to myofibrillar volume fraction was largely unchanged during hypertrophy but was reduced by 25% compared with controls after termination of growth at 35 days. During the process of hypertrophy which eventually led to an increase in average single cell volume of the cardiomyocytes by 78%, the volume fraction and the numerical density of AVs was significantly lower than in sham-operated rats. The most striking difference was observed 7 days after the operations, the stage at which the growth rate of the cardiomyocytes relative to controls was at its maximum of 4.5% per day. At this point the volume fraction as well as the numerical density of AVs were reduced by about 50% compared with controls. At 14 and 21 days after operation, when the relative growth rate of the hypertrophying cardiomyocytes was still 2% and 1% per day, the AV volume fraction was reduced to a lesser extent (by 47% and 28%, respectively). After termination of adaptive growth at 35 days significant differences in fractional volume and numerical density of AVs were no longer detectable. These results suggest that degradation of cytoplasmic components is inhibited in cardiomyocytes undergoing hypertrophy. Such an anticatabolic reaction seems to play an important role in establishing the positive balance of cellular metabolism generally required for growth processes.

Effect of insulin and lack of effect of workload and hypoxia on protein degradation in the perfused working rat heart

1. Protein degradation was studied in the glucose (5 mM)-perfused working rat heart preparation of Taegtmeyer, Hems & Krebs [(1980) Biochem. J. 186. 701-711]. 2. The effects of cardiac workload were investigated in three different preparations: (a) control (low workload), (b) increased pressure workload (simulating conditions of aortic pressure in vivo) and (c) increased volume workload. There was no effect of increased workload on protein degradation in preparation (b) or (c) when compared with preparation (a). Insulin inhibited protein degradation in all three preparations. Significantly greater inhibition by insulin was observed in the increased-pressure-workload preparation (b). 3. Hypoxia was induced by the partial replacement of O2 in the gaseous phase by N2. Hearts maintained their cardiac output when O2 content was decreased from 95% to 55% by volume, but the stability of the preparation was less at 50% O2. Lactate output was significantly increased at O2 contents of 65% or less. The rate of protein degradation was not different from control values (95% O2) in perfusions with 65, 55 or 50% O2. 4. We conclude that acutely increased workload or acute hypoxia does not affect protein degradation in the perfused working rat heart when cardiac output is relatively stable.

Effects of cardiac work and leucine on protein turnover

The purpose of these experiments was to assess effects of cardiac work and leucine in hearts supplied only glucose or substrate and hormone mixtures that simulated plasma. Rates of protein degradation greatly exceeded protein synthesis in Langendorff preparations supplied glucose. This severely negative nitrogen balance was brought closer to zero by provision of more complete substrate mixtures. Cardiac work further improved the nitrogen balance by stimulating protein synthesis in hearts supplied glucose (mixture 1), glucose-insulin-glucagon-lactate-beta-hydroxybutyrate (mixture 2), or palmitate-beta-hydroxybutyrate-glucose (mixture 3) and inhibiting protein degradation in hearts supplied glucose. Cardiac work did not affect the rates of either protein synthesis or degradation in hearts provided insulin-lactate-glucose (mixture 4). The increase in protein synthesis was associated with increased rates of peptide chain initiation. Addition of 1 mM leucine had an additional effect to restore nitrogen balance to zero or to achieve positive balance in working hearts supplied substrate and hormone mixture 2.

The effects of glucose, acetate, lactate and insulin on protein degradation in the perfused rat heart

Rat hearts were perfused as working preparations by the method of Taegtmeyer, Hems & Krebs [(1980 Biochem. J. 186, 701--711]. In the presence of glucose, insulin significantly inhibited protein degradation at concentrations as low as 50 mu units/ml. Acetate or lactate, when present either as sole fuel for contraction or in combination with glucose, did not inhibit protein degradation. Insulin inhibition or protein degradation was decreased with either lactate as sole fuel. We suggest that the inhibition of protein degradation occurs over the normal range of plasma concentrations of insulin present in vivo and that the presence of glucose may be at least in part necessary for this effect of insulin.

Effect of exercise on amino acid incorporation into myocardial contractile proteins

Amino acid incorporation into myocardial protein was studied in rats after an acute bout of exhaustive swimming. Hearts were removed at exhaustion, 1, 2, or 4 h of recovery and amino acid incorporation measured using [3H] phenylalanine in an isolated perfused heart preparation. Amino acid incorporation into total tissue protein was reduced 30% at exhaustion but returned to normal by 1 h of recovery and showed no further change 4 h post exercise. In the myofibrillar fraction amino acid incorporation decreased slightly after exhaustive exercise but was stimulated by 57% following 2 h recovery. Myosin, electrophoretically fractionated showed an 84% stimulation in phenylalanine incorporation at exhaustion and 112% increase 2 h post exercise. Amino acid incorporation into myosin light chains (LC1 and LC2) accounted for most of the increased rate of synthesis. These data suggest that there was a preferential increase in myocardial protein synthesis following exercise which was associated with the myosin light chain components of the contractile proteins.

Relative synthesis of cardiac contractile proteins. Evidence for synthesis from the same precursor pool

The relative molar synthesis of cardiac contractile proteins has been measured in the perfused heart under control haemodynamic conditions. This synthesis, of myosin heavy chains, individual light chains (1 and 2), actin and tropomyosin, was determined from isolated guinea-pig hearts perfused for 3h simultaneously with constant specific radioactivities and concentrations of [3H]lysine and [3H]phenylalanine. The data strongly suggest that all of the proteins studied were synthesized from the same precursor pools of lysine and phenylalanine, since the ratio of the specific activities of the two labels was the same in all of the proteins. Measurement of molar synthesis of each contractile protein was the same with either labelled amino acid. Under control haemodynamic-perfusion conditions, the relative molar synthesis of the contractile proteins was actin greater than heavy chains greater than light chain 2 greater than light chain 1 greater than tropomyosin.

Regulation of protein synthesis and degradation during in vitro cardiac work

Cardiac work increased protein synthesis in hearts supplied glucose (mixture 1), glucose-insulin-glucagon-lactate-beta-hydroxybutyrate (mixture 2) or palmitate-beta-hydroxybutyrate-glucose (mixture 3). In hearts provided mixture 1, acceleration of synthesis involved increased rates of peptide chain initiation. In these hearts intracellular concentrations of 5 amino acids decreased and 13 others were unchanged, indicating that faster protein synthesis did not depend on increased amino acid availability. In hearts supplied mixtures 2, 3, or 4 (lactate-glucose-insulin), intracellular concentrations of branched-chain amino acids were decreased by work, whereas intracellular levels of some acidic and neutral amino acids increased. Protein degradation was decreased by work in hearts supplied mixtures 1 and 2, but not mixtures 3 and 4. In hearts provided mixture 1, nitrogen balance was negative, but less so in working preparations. Nitrogen balance was zero or positive in working hearts provided mixtures 2 and 4. These studies indicated that in hearts supplied some, but not all, of the substrate mixtures, cardiac work maintained efficiently of protein synthesis and inhibited protein degradation. An improved method for perfusion of working hearts with albumin-containing buffer is described.

Determination in vitro of the rate of protein synthesis and degradation in human-skeletal-muscle tissue

The present studies were aimed to evaluate the possibility to use a system for estimation in vitro of the biosynthesis and degradation rates of human skeletal muscle protein. A previously characterized human skeletal muscle preparation was used. Amino acids and insulin stimulated significantly the incorporation rate of leucine into proteins. The effect of amino acids was more pronounced than that of insulin. The stimulatory effect of insulin could be decreased by amino acids. Insulin did not influence the tissue uptake or the oxidation rate of leucine. The release of [14C]leucine deriving from degradation of prelabelled skeletal muscle fibre proteins was linear for at least 2.5 h of incubation and optimal with leucine at concentrations beyond 12.5 mmol/1 or in the presence of puromycin in the incubation medium. The rate of the release of radioactivity was significantly inhibited by amino acids and at borderline significance by insulin but not by puromycin. The specific radioactivity in prelabelled proteins decreased significantly in the presence of puromycin suggesting that leucine derived from protein degradation was reutilized in vitro. This reutilization was found to be 9 +/- 1% of leucine released from degradation of proteins in 30 subjects. A statistically significant positive correlation between the cathepsin D activity in human skeletal muscle tissue and the degradative rate of prelabelled muscle proteins in vitro was observed. The results indicate that biosynthesis and degradation of skeletal muscle proteins in this system in vitro were subjected to control mechanisms. It is suggested that the release of radioactivity from prelabelled muscle fibre proteins during incubation probably only reflects the degradation of some rapidly-turning-over proteins.

Heart contractile proteins

That several proteins of the sarcomere differ from one muscle to the next is well documented, and it is becoming evident that homogeneous muscles, like the heart, are also species specific. 1) Clear-cut evidence is available concerning myosin, and, to date, several types of molecules have been described. a) The myosins of white skeletal, heart, and smooth muscle differ in the activity of their Ca2+ and K+ATPases, as also in the structure of their light subunits. b) The Ca2+ATPases of the various cardiac myosins have been shown to exhibit species differences and correlate with the speed of shortening of the muscle. 2) The structures of tropomyosin, some troponin components, and alpha actinin (but not actin) appear to be unlike in the different types of muscle. 3) These phylogenic modifications may be related to the changes characteristic of the particular muscles under pathological conditions, which are accompanied by substantial increase in protein synthesis.

Protein degradation to low-molecular compounds after death and during reanimation

The process of protein degradation to amino acids and peptides in rabbits following death and during reanimation in terms of the effects of artificial postmortem cooling on that process has been studied. Protein degradation was judged by increase of low-molecular nitrogenous compounds in serum and in organs by increase in soluble radioactivity with time in animals the proteins of which had been marked in vivo with radioisotopes. It has been found that immediately after death resulting from acute anoxia the processes of protein degradation to amino acids as well as synthesis stops in liver, skeletal and cardiac muscles, spleen, brain and spinal cord. Similar phenomenon takes place in the case of deep hypothermy. During reanimation the process of protein degradation to low-molecular compounds in organs restores.

The effect of pressure or flow stress on right ventricular protein synthesis in the face of constant and restricted coronary perfusion

Cardiac stress produced by hypertension or excess volume loading results in different types of hypertrophy. Elevated left ventricular pressure rapidly results in increased myocardial protein synthesis in vivo and in vitro, but such rapid alterations are not consistently seen in volume loading. The difference in response is difficult to clarify since it is not possible to effect alterations in left ventricular pressure or perfusion without profoundly affecting coronary perfusion. The present study describes cardiac protein synthesis in the right ventricle of the young guinea pig heart in vitro by utilizing a perfusion model in which the right ventricle could be stressed by elevations of pressure or volume loading in the presence of constant and restricted coronary perfusion. With coronary flow maintained at 4 ml/min per heart equivalent to 25 ml/min/g dry wt, an increase in right ventricular pressure from normal levels of 3 mm Hg to 11 mm Hg resulted in a 60 percent increase of myocardial incorporation of (14C)lysine into protein. However, with further increases of right ventricular pressure to 22 mm Hg, protein synthesis dropped back to normal levels. The falloff in protein synthesis was not due to decreased contractility, alterations in intracellular lysine pool specific activity, or alterations in distribution of coronary flow. a 60 percent increase in coronary perfusion was again associated with a similar response of protein synthesis to progressive elevations of pressure despite a rise in the ATP levels and a fall in lactate production. Thus, a deficiency of O2 did not entirely explain the decline of protein synthesis with maximal pressures. At all levels of coronary perfusion, volume loading for 3 h did not result in increased protein incorporation of (14C)lysine. The studies support a relationship between ventricular pressure and protein synthesis unrelated to coronary flow per se. A pressure receptor triggering protein synthesis within the ventricular wall is postulated. Such a relationship is not apparent in short-term volume loading in vitro.

Effects of ethanol on protein synthesis

Cardiac: Cardiac protein synthesis is influenced by the state of nutrition with reduction of cardiac size in starvation. Ethanol per se may not affect this synthesis directly, but the metabolite of ethanol, acetaldehyde, profoundly decreases normal protein synthesis in the heart in vitro. The interference with the synthetic process may play a role in the ultimate cardiomyopathies of malnutrition and alcoholism. Hepatic: In vivo albumin synthesis is sensitive to environment, oncotic pressure, normal balance, nutrition, as well as toxins and state of health. Thus, to study the acute effects of alcohol alone, it was necessary to employ the isolated perfused liver. Fasting reduced albumin synthesis 50%, with loss of RNA and a disaggregation of the endoplasmic membrane bound polysome. Tryptophan, arginine and ornithine added to the perfusate at a final concentration of 10 mM reversed these findings. Alcohol likewise reduced albumin synthesis; disaggregates the bound polysome without a marked loss of RNA. Ornithine, arginine and tryptophan are able to reverse this loss in albumin synthesizing capacity. The combination of fasting and alcohol, while not lowering albumin synthesis below that seen with either stress alone, prevents the recovery from either stress.