scholarly journals Effects of pressure overload and insulin on protein turnover in the perfused rat heart. Prostaglandins are not involved although their synthesis is stimulated by insulin

1987 ◽  
Vol 243 (2) ◽  
pp. 473-479 ◽  
Author(s):  
D M Smith ◽  
P H Sugden
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Rat Heart ◽  
Pressure Overload ◽  
Aortic Pressure ◽  
Prostaglandin Synthesis ◽  
Perfused Rat Heart ◽  
Heart Preparation ◽  
Synthesis And Degradation

A modified anterogradely perfused rat heart preparation is described in which all the cardiac output passes through the coronary circulation. Such a preparation develops hypertensive aortic pressures. Hypertensive aortic pressures or insulin stimulate the rate of cardiac protein synthesis and inhibit the rate of protein degradation. Aortic pressure and insulin may be important in the regulation of cardiac nitrogen balance in vivo. By abolishing cardiac prostaglandin synthesis with 4-biphenylacetate, we were able to investigate the possible involvement of prostaglandins in the modulation of protein turnover by pressure overload or insulin. There was no evidence of any involvement. However, insulin stimulated and cycloheximide inhibited cardiac prostaglandin synthesis. These findings are consonant with an enzyme involved in prostaglandin synthesis being short-lived and prostaglandin synthesis being rapidly influenced by activators and inhibitors of protein synthesis and degradation.

Aortic perfusion pressure as early determinant of beta-isomyosin expression in perfused hearts

1992 ◽  
Vol 263 (5) ◽  
pp. H1537-H1545
Author(s):  
C. Delcayre ◽  
D. Klug ◽  
V. T. Nguyen ◽  
C. Mouas ◽  
B. Swynghedauw
Keyword(s):  
Protein Synthesis ◽  
Total Protein ◽  
Stress Protein ◽  
Pressure Overload ◽  
Aortic Pressure ◽  
Mechanical Stimulus ◽  
Beating Heart ◽  
Specific Gene ◽  
Coronary Pressure

Pressure overload in vivo induces an increase in cardiac protooncogene and stress protein expression that may initiate the long-term genetic changes observed in hypertrophy. To known whether mechanical stimulus is linked to specific gene transcription, expression of immediate early genes and synthesis of total proteins and myosin heavy chains (MHCs) were studied in beating and KCl-arrested isolated rat hearts perfused for 2 h under various coronary pressures. The main result of this study is that in the beating heart an augmentation of aortic pressure from 60 to 120 mmHg results in a pronounced enhancement of the synthesis of MHC (+59%) and of the expression of the beta-MHC isomyosin mRNA (iso-mRNA; +104%). Also, total protein synthesis and the amounts of poly-(A)+, c-fos, c-myc, and heat-shock protein HSP68 mRNAs were increased. To arrest the heart at 60 mmHg has no effect on total protein synthesis and on the amounts of poly(A)+, alpha-MHC and beta-MHC iso-mRNAs, and mRNAs coding for oncoproteins, but the synthesis of MHC decreased by 24%. By contrast with what we have observed in the beating heart, the augmentation of the coronary pressure in the arrested heart stimulates total protein synthesis and increases the amount of poly(A)+, c-fos, c-myc, and HSP68 mRNAs but has no effect on the expression of both MHC iso-mRNAs. In conclusion, the activation of myosin synthesis by high coronary pressure in this model has mainly a pretranslational origin when the heart is beating.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of cysteine on protein and coenzyme A synthesis in rat heart

1984 ◽  
Vol 247 (1) ◽  
pp. C99-C106 ◽  
Author(s):  
B. H. Chua ◽  
K. E. Giger ◽  
B. J. Kleinhans ◽  
J. D. Robishaw ◽  
H. E. Morgan
Keyword(s):  
Protein Synthesis ◽  
Rat Heart ◽  
Coenzyme A ◽  
Pantothenic Acid ◽  
Fold Increase ◽  
Creatine Phosphate ◽  
Aortic Pressure ◽  
Protective Agent ◽  
Bicarbonate Buffer ◽  
Perfused Rat Heart

The effect of cysteine availability on protein and coenzyme A (CoA) synthesis in perfused rat heart was incompletely evaluated in earlier experiments because rapid conversion of cysteine to cystine occurred when the perfusion buffer was oxygenated. This conversion was minimized by addition of an excess of reducing agents such as dithiothreitol or mercaptodextran or by provision of bathocuproine disulfonate, a copper chelator. Dithiothreitol was not a suitable protective agent because it reduced ATP and creatine phosphate contents. Perfusion of hearts with [35S]cystine or [35S]cysteine in the presence of mercaptodextran resulted in a 22-fold or 5-fold increase, respectively, in incorporation of [35S] into protein and a 5-fold or 8-fold increase, respectively, in incorporation into CoA compared with hearts supplied [35S]cystine or [35S]cysteine without the reducing agent. When compared with hearts perfused at an aortic pressure of 90 mmHg with bicarbonate buffer that contained 15 mM glucose, 25 mU insulin/ml, 0.4 mM [14C]phenylalanine, no cysteine and plasma levels of other amino acids, provision of 0.09 or 0.2 mM cysteine alone or in the presence of mercaptodextran, or bathocuproine disulfonate enhanced rates of protein synthesis 16-35%. When 0.2 mM cysteine was added to bicarbonate buffer containing 7 microM pantothenic acid, supplementation with mercaptodextran or bathocuproine disulfonate was required to raise CoA content. These results indicated that an exogenous supply of cysteine was needed to maintain maximal rates of protein and CoA synthesis in the perfused rat heart. Protective compounds were required to obtain the cysteine effect on CoA but not on protein synthesis.

scholarly journals Some factors affecting phosphate transport in a perfused rat heart preparation

1980 ◽  
Vol 188 (2) ◽  
pp. 297-311 ◽  
Author(s):  
G Medina ◽  
J Illingworth
Keyword(s):  
Rat Heart ◽  
Prolonged Exposure ◽  
Work Load ◽  
Phosphate Transport ◽  
Aortic Pressure ◽  
Efflux Rate ◽  
Cardiac Work ◽  
Factors Affecting ◽  
Perfused Rat Heart ◽  
Heart Preparation

Pi uptake by a perfused rat heart preparation did not require the presence of any other permeant anion, but was markedly dependent on the extracellular Na+ concentration and accelerated when tissue oxygenation was inadequate. Pi efflux was also independent of other permeant anions, but apparently varied with the intracellular Na+ concentration. Cardiac Pi efflux was not sensitive to a number of inhibitors that clock Cl- movement in heart and other tissues. Both uptake and efflux apparently proceed via a reversible electroneutral co-transport system linked to the transmembrane Na+ gradient. Pi uptake was independent of cardiac work load, but the efflux rate was sharply accelerated after an increase in aortic pressure development, with a slow return towards basal values during sustained periods of high work output. An inverted biphasic effect on the efflux rate was observed after a reduction in cardiac work load. Mild hypoxia and respiratory and metabolic acidosis each resulted in a transient acceleration of Pi efflux followed by a return towards basal values during prolonged exposure to the stimulus, whereas respiratory and metabolic alkalosis produced a similar but inverted response. The origin of these phasic effects on Pi efflux remains to be identified at present.

scholarly journals A comparison of rates of protein turnover in rat diaphragm in vivo and in vitro

1986 ◽  
Vol 233 (1) ◽  
pp. 279-282 ◽  
Author(s):  
V R Preedy ◽  
D M Smith ◽  
P H Sugden
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Rat Diaphragm ◽  
Degradation Rates ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

Protein synthesis and degradation rates in diaphragms from fed or starved rats were compared in vivo and in vitro. For fed rats, synthesis rates in vivo were approximately twice those in vitro, but for starved rats rates were similar. Degradation rates were less in vivo than in vitro in diaphragms from either fed or starved rats.

Respiratory energy requirements and rate of protein turnover in vivo determined by the use of an inhibitor of protein synthesis and a probe to assess its effect

1994 ◽  
Vol 92 (4) ◽  
pp. 585-594 ◽  
Author(s):  
T. J. Bouma ◽  
R. De Visser ◽  
J. H. J. A. Janssen ◽  
M. J. De Kock ◽  
P H. Van Leeuwen ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Energy Requirements ◽  
Inhibitor Of Protein Synthesis

scholarly journals The effect of protein depletion and repletion on muscle-protein turnover in the chick

1981 ◽  
Vol 194 (3) ◽  
pp. 811-819 ◽  
Author(s):  
M L MacDonald ◽  
R W Swick
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Control Diet ◽  
Breast Muscle ◽  
Synthesis Rate ◽  
Protein Depletion ◽  
Protein Mass ◽  
Fractional Rate

Rates of growth and protein turnover in the breast muscle of young chicks were measured in order to assess the roles of protein synthesis and degradation in the regulation of muscle mass. Rates of protein synthesis were measured in vivo by injecting a massive dose of L-[1-14C]valine, and rates of protein degradation were estimated as the difference between the synthesis rate and the growth rate of muscle protein. In chicks fed on a control diet for up to 7 weeks of age, the fractional rate of synthesis decreased from 1 to 2 weeks of age and then changed insignificantly from 2 to 7 weeks of age, whereas DNA activity was constant for 1 to 7 weeks. When 4-week-old chicks were fed on a protein-free diet for 17 days, the total amount of breast-muscle protein synthesized and degraded per day and the amount of protein synthesized per unit of DNA decreased. Protein was lost owing to a greater decrease in the rate of protein synthesis, as a result of the loss of RNA and a lowered RNA activity. When depleted chicks were re-fed the control diet, rapid growth was achieved by a doubling of the fractional synthesis rate by 2 days. Initially, this was a result of increased RNA activity; by 5 days, the RNA/DNA ratio also increased. There was no evidence of a decrease in the fractional degradation rate during re-feeding. These results indicate that dietary-protein depletion and repletion cause changes in breast-muscle protein mass primarily through changes in the rate of protein synthesis.

Fiber-type composition of nine rat muscles. II. Relationship to protein turnover

1989 ◽  
Vol 257 (6) ◽  
pp. E828-E832 ◽  
Author(s):  
P. J. Garlick ◽  
C. A. Maltin ◽  
A. G. Baillie ◽  
M. I. Delday ◽  
D. A. Grubb
Keyword(s):  
Protein Synthesis ◽  
Regression Analysis ◽  
Protein Turnover ◽  
Fiber Type ◽  
Female Rats ◽  
Protein Breakdown ◽  
Fiber Type Composition ◽  
Type Composition ◽  
Age Regression

Rates of protein synthesis in vivo and fiber-type composition were measured in nine limb muscles of female rats at ages ranging from weaning to 1 yr. In all muscles, there was a decline in protein synthesis with increasing age, mostly as a result of a fall in the RNA content. Rates of protein breakdown and growth were determined in six muscles and these also declined with age. Regression analysis of the data for all ages showed that protein synthesis was correlated with the content of slow oxidative fibers but not with the relative proportions of fast glycolytic to fast oxidative glycolytic fibers.

Effects of food deprivation on protein synthesis and degradation in rat skeletal muscles

1976 ◽  
Vol 231 (2) ◽  
pp. 441-448 ◽  
Author(s):  
JB Li ◽  
AL Goldberg
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Food Deprivation ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Rna Content ◽  
Fasted Rats ◽  
Synthesis And Degradation

The effects of food deprivation on protein turnover in rat soleus and extensor digitorum longus (EDL) were investigated. Muscles were removed from fed or fasted growing rats, and protein synthesis and breakdown were measured during incubation in vitro. Rates of synthesis and degradation were higher in the dark soleus than in the pale EDL. One day after food removal protein synthesis and RNA content in the EDL decreased. On the 2nd day of fasting, rates of protein catabolism in this muscle increased. Little or no change in synthesis and degradation occurred in the soleus. Consequently, during fasting the soleus lost much less weight than the EDL and other rat muscles. In unsupplemented buffer or in medium containing amino acids, glucose, and insulin, the muscles of fasted rats showed a lower rate of protein synthesis expressed per milligram of tissue but not per microgram of RNA. Thus the decrease in muscle RNA on fasting was responsible for the reduced synthesis observed under controlled in vitro conditions. In vivo the reduction in muscle protein synthesis on fasting results both from a lower RNA content and lower rate of synthesis per microgram of RNA. Reduced supply of glucose, insulin, and amino acids may account for the lower rate of synthesis per microgram of RNA demonstrable in vivo.

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