Protein synthesis during right-ventricular hypertrophy after pulmonary-artery stenosis in the dog

Everett, Alan; Taylor, Roger R.; Sparrow, Malcolm

doi:10.1042/bj1660315

Cited by 38 publications

(19 citation statements)

References 18 publications

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“…Although amino acids may be weak insulin secretagogues, we observed no change in insulin concentration during the course of the current study. Likewise, hemodynamic factors that alter ventricular tension development have a clinically recognized long-term effect on heart mass and appear to be important determinants of myocardial protein synthesis experimentally (39). Insofar as arterial blood pressure, cardiac double product, myocardial oxygen consumption, and coronary blood flow did not increase significantly, increased myocardial work does not appear responsible for the altered protein metabolism seen with BCAA infusion.…”

Section: Discussionmentioning

confidence: 89%

Myocardial protein turnover in patients with coronary artery disease. Effect of branched chain amino acid infusion.

Young¹,

McNulty²,

Morgan³

et al. 1991

J. Clin. Invest.

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The regulation of protein metabolism in the human heart has not previously been studied. In 10 postabsorptive patients with coronary artery disease, heart protein synthesis and degradation were estimated simultaneously from the extraction ofintravenously infused L-[ring-2,6-3Hjphenylalanine (PHE) and the dilution of its specific activity across the heart at isotopic steady state. We subsequently examined the effect of branched chain amino acid (BCAA) infusion on heart protein turnover and on the myocardial balance of amino acids and branched chain ketoacids (BCKA) in these patients.In nmol PHE/min). BCAA infusion stimulated the myocardial uptake of both BCAA (P < 0.005) and their ketoacid conjugates (P < 0.001) in proportion to their circulating concentrations. Net uptake of the BCAA greatly exceeded that of other essential amino acids suggesting a role for BCAA and BCKA as metabolic fuels. Plasma insulin levels, cardiac double product, coronary blood flow, and myocardial oxygen consumption were unchanged. These results demonstrate that the myocardium of postabsorptive humans is in negative protein balance and indicate a primary anabolic effect of BCAA on the human heart. (J.

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Section: Discussionmentioning

confidence: 89%

Myocardial protein turnover in patients with coronary artery disease. Effect of branched chain amino acid infusion.

Young¹,

McNulty²,

Morgan³

et al. 1991

J. Clin. Invest.

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“…The synthesis of myofibrillar proteins such as actin and myosin are increased in order to facilitate net accumulation of protein and subsequent assembly into nascent myofibrils (27)(28)(29). In the electrical stimulation model used in this study, there was no measurable accumulation of myosin and/or total cell protein over the 4-h time period.…”

Section: Discussionmentioning

confidence: 99%

Contraction Accelerates Myosin Heavy Chain Synthesis Rates in Adult Cardiocytes by an Increase in the Rate of Translational Initiation

Ivester

Tuxworth

Cooper

et al. 1995

Journal of Biological Chemistry

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The purpose of this study was to determine the mechanism by which contraction acutely accelerates the synthesis rate of the contractile protein myosin heavy chain (MHC). Laminin-adherent adult feline cardiocytes were maintained in a serum-free medium and induced to contract at 1 Hz via electrical field stimulation. Electrical stimulation of contraction accelerated rates of MHC synthesis 28%, p < 0.05 by 4 h as determined by incorporation of [ 3 H]phenylalanine into MHC. MHC mRNA expression as measured by RNase protection was unchanged after 4 h of electrical stimulation. MHC mRNA levels in messenger ribonucleoprotein complexes and translating polysomes were examined by sucrose gradient fractionation. The relative percentage of polysomebound MHC mRNA was equal at 47% in both electrically stimulated and control cardiocytes. However, electrical stimulation of contraction resulted in a reproducible shift of MHC mRNA from smaller polysomes into larger polysomes, indicating an increased rate of initiation. This shift resulted in significant increases in MHC mRNA levels in the fractions containing the larger polysomes of electrically stimulated cardiocytes as compared with nonstimulated controls. These data indicate that the rate of MHC synthesis is accelerated in contracting cardiocytes via an increase in translational efficiency.Hypertrophic growth occurs in terminally differentiated adult cardiocytes by an increase in cellular mass via a relatively coordinate increase in the proteins comprising each of the cellular components (1). This accumulation of cardiocyte proteins occurs by an increase in rates of protein synthesis relative to rates of protein degradation (2). The anabolic changes that occur during hypertrophy of the adult myocardium are generally considered to be a compensatory response to an increase in hemodynamic load (3). As demonstrated in studies employing isolated papillary muscle preparations, both the active tension and passive strain components of load have been identified as mechanical stimuli for accelerating protein synthesis rates in adult myocardium (4, 5). These findings have been extended to isolated adult cardiocytes in culture. Rates of protein synthesis were accelerated in response to electrically stimulated cardiocyte contraction (6, 7), in response to a basal load as defined by adherence of the cardiocytes to the culture dish and establishment of a resting length (8) and in response to passive stretch of cardiocytes adherent to a deformable membrane (9). Thus, the integrity of adult cardiocytes in primary culture is maintained with respect to the ability to transduce changes in mechanical load into an anabolic response such as accelerated protein synthesis rate.The specific mechanisms by which cardiocyte protein synthesis is regulated probably occur at many levels, including transcriptional, post-transcriptional, and translational processes (10). It is well established, for example, that transcriptional and post-transcriptional mechanisms regulate steady state mRNA levels and are respon...

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“…It is interesting that Schreiber found when protein synthesis was measured in KCl-arrested, but perfused, guinea pig hearts, there was no sign of a decrease in protein synthesis [193]. In right ventricular hypertrophy consequent on pulmonary artery stenosis in dog, the rate of protein synthesis doubled by day 5 and was still significantly elevated at day 24 [229]. It would be very useful to have some data for arrested but perfused hearts of other species to supplement Schreiber's guinea pig data.…”

Section: Modifiers Of Basal Metabolismmentioning

confidence: 99%

“…In general, in compensated long-term pressure overload the literature consensus has been to report a decrease in basal metabolism, but in the early stages of hypertrophy, when protein synthesis is markedly stimulated [2,229,230], it would not be surprising if basal metabolism were to be stimulated.…”

Section: Modifiers Of Basal Metabolismmentioning

confidence: 99%

Cardiac Basal Metabolism.

Gibbs

Loiselle²

2001

JJP

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The cardiac basal metabolism is the rate of energy expenditure of the quiescent myocardium. It is also called the resting metabolism or the arrested heart metabolism. It has been measured in numerous ways, and in vivo there is good evidence that it accounts for about 1/5 to 1/3 of the total energy flux. The difficulty arises, however, when the heart is stopped because the magnitude of the basal metabolism depends, as blood viscosity, on how and under what physiological condition it is measured. It is possible for the in vivo basal value to fall to less than 1/5 of its original value without cellular damage or to increase to values 5 times greater than its probable in vivo magnitude (i.e., to rise to values in excess of the energy flux of the normally beating heart) by altering the composition of the perfusion medium. We have written on this subject several times [1][2][3], but believe that developments in knowledge now make it possible for us to speculate in a more informed manner. Since several million openheart operations are performed on arrested hearts worldwide each year, it would seem imperative that we understand the cellular mechanisms that can change the magnitude of basal metabolism.A. V. Hill [4] has pointed out that in examining physiological activities, it is necessary to assume a baseline from which some quantity or rate can be measured. If the energy flux produced by the beating heart were very large compared with the energy flux of the arrested heart, baseline ambiguity would be relatively unimportant. But this is not so in regard to the heart; its basal metabolism is high. Within a species, the basal metabolism of cardiac tissue is several-fold higher than the resting metabolism of skeletal muscle and is an order of magnitude greater than the resting metabolism of amphibian skeletal muscle.Species differences are clearly evident in the magnitude of cardiac basal metabolism, and we believe that the major reason for these differences relates to the leakiness of cell membranes, such as those of the sarcolemma and sarcoplasmic reticulum and those of Japanese Journal of Physiology, 51, 399-426, 2001 Key words: whole hearts, isolated preparations, biochemical contributors, modifiers, species difference, temperature, substrate, hypoxia. Abstract:We endeavor to show that the metabolism of the nonbeating heart can vary over an extreme range: from values approximating those measured in the beating heart to values of only a small fraction of normal-perhaps mimicking the situation of nonflow arrest during cardiac bypass surgery. We discuss some of the technical issues that make it difficult to establish the magnitude of basal metabolism in vivo. We consider some of the likely contributors to its magnitude and point out that the biochemical reasons for a sizable fraction of the heart's basal ATP usage remain unresolved. We consider many of the physiological factors that can alter the basal metabolic rate, stressing the importance of substrate supply. We point out that the protective effect of hypothermia ...

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Protein synthesis during right-ventricular hypertrophy after pulmonary-artery stenosis in the dog

Cited by 38 publications

References 18 publications

Myocardial protein turnover in patients with coronary artery disease. Effect of branched chain amino acid infusion.

Myocardial protein turnover in patients with coronary artery disease. Effect of branched chain amino acid infusion.

Contraction Accelerates Myosin Heavy Chain Synthesis Rates in Adult Cardiocytes by an Increase in the Rate of Translational Initiation

Cardiac Basal Metabolism.

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