ABSTRACT
A decrease in the rate of protein synthesis as well as an increase in the synthesis time of "medium-size" polypeptide chain were detected in total rabbit myocardium ischemia, which were evaluated using rabbit myocardium cell-free protein-synthesizing systems. The decrease in the synthesis rate of total myocardial proteins was shown to depend on the state of ribosomes function. Redistribution in the pools of membrane-bound and free ribosomes as well as a decrease of polyribosomes amount in total pool of myocardial ribosomes were observed under conditions of total myocardial ischemia.
Subject(s)
Coronary Disease/metabolism , Myocardium/metabolism , Protein Biosynthesis , Animals , Cell-Free System , Cytosol/metabolism , Kinetics , Male , RNA, Messenger/metabolism , Rabbits , Ribosomes/metabolismABSTRACT
Catalytic properties and thermostability of leucyl-tRNA-synthetase were studied both in free form and in the form of high molecular complexes, isolated from pig myocardium under normal state and after 15 min and 30 min ischemia. Km values of free and associated forms of leucyl-tRNA-synthetase were similar either in normal state or after 15-30 min ischemia. Complex-formation protected the enzyme from thermic inactivation under normal and ischemic conditions. Reverse redistribution of the leucyl-tRNA-synthetase activity was found in the fractions of free enzyme and high molecular complex depending on duration of ischemia.
Subject(s)
Amino Acyl-tRNA Synthetases/metabolism , Coronary Disease/enzymology , Leucine-tRNA Ligase/metabolism , Myocardium/enzymology , Animals , Catalysis , Hot Temperature , Kinetics , SwineABSTRACT
Distribution of the aminoacyl-tRNA synthetase activity has been studied in the normal rabbit liver cells and in the model of protein synthesis damage, i.e. under experimental myocardial infarction (EMI). The activity of a number of aminoacyl-tRNA synthetases in postmitochondrial and postribosomal extracts from rabbit liver homogenate has been determined to increase 12 h after EMI. Gel filtration of the postribosomal extract on Sepharose 6B shows that the activity of aminoacyl-tRNA synthetases is distributed among the fractions with Mr 1.82 x 10(6), 0.84 x 10(6) and 0.12 = 0.35 x 10(6). The first two fractions (high-molecular-weight aminoacyl-tRNA synthetase complexes) contain arginyl-, glutamyl-, isoleucyl-, leucyl-, lysyl- and valyl-tRNA synthetases, whereas the low-molecular-weight fraction contains alanyl-, arginyl-, glycyl-, phenylalanyl-, seryl-, threonyl-, tryptophanyl- and tyrosyl-tRNA synthetases. In a case of EMI all the aminoacyl-tRNA synthetases translocate from the complexes with Mr 1.82 x 10(6) into the complexes with Mr 0.84 x 10(6), what provided evidence for the possibility to regulate protein synthesis by changes in compartmentalization of aminoacyl-tRNA synthetases.
Subject(s)
Amino Acyl-tRNA Synthetases/metabolism , Liver/enzymology , Myocardial Infarction/enzymology , Protein Biosynthesis , Animals , Chromatography, Gel , Liver/metabolism , Myocardial Infarction/metabolism , RabbitsABSTRACT
Distinct decrease in the rate of aminoacylation of tRNAs, specific to alanine, glutamic acid, leucine and serine, was found after 20 min anoxia of perfused pig heart. In the anoxia activity of aminoacyl-tRNA synthetases of the same amino acid specificity was increased. Reduction of these macromolecules activity was observed in reoxygenation of the anoxic myocardium. Biological activity of tRNA and aminoacyl-tRNA synthetases in pig myocardium appears to depend on the supply of heart with oxygen.
Subject(s)
Amino Acyl-tRNA Synthetases/metabolism , Myocardium/metabolism , Oxygen/pharmacology , RNA, Transfer/metabolism , Animals , In Vitro Techniques , Myocardium/enzymology , Protein Biosynthesis , SwineABSTRACT
In pig myocardial extracts autolyzed within 15 min alanyl-, glycyl-, glutamyl-, leucyl- and seryl-tRNA synthetase activities were increased as compared with controls. The enzymatic activities were decreased after autolysis for 30 min. The 15 min autolysis was shown to decrease the molecular mass of the glycyl-tRNA synthetase complex. Within both 15 min and 30 min autolysis inorganic pyrophosphatase was markedly activated either in myocardium extracts or in high molecular complexes; this phenomenon may be responsible for activation of a number of aminoacyl-tRNA synthetases.
Subject(s)
Amino Acyl-tRNA Synthetases/metabolism , Autolysis/enzymology , Coronary Disease/enzymology , Myocardium/enzymology , Amino Acids/metabolism , Animals , Coronary Disease/pathology , In Vitro Techniques , Inorganic Pyrophosphatase , Molecular Weight , Myocardium/pathology , Pyrophosphatases/metabolism , SwineABSTRACT
The content of serum albumin in rabbit blood was found to be lowered within the first day after reproduction of experimental myocardial infarction. The rate and the level of translation of endogenous mRNA were studied in cell-free systems from normal rabbit liver and 6-12-24 h after experimental myocardial infarction. The decrease of the total protein synthesis in the crude cell-free system from the liver of experimental animals was shown to depend on the lack of energy supply rather than on the reduced activity of the protein-synthesizing apparatus. The relative drop of protein synthesis in the cell-free system with saturating concentration of ATP, GTP and creatine phosphate is likely to be connected with a decrease in the proportion of membrane-bound polysomes.
Subject(s)
Liver/metabolism , Myocardial Infarction/metabolism , Protein Biosynthesis , Animals , Blood Proteins/analysis , Cell-Free System , RNA, Messenger/metabolism , Rabbits , Serum Albumin/analysis , Time FactorsABSTRACT
A number of aminoacyl-tRNA synthetases from rabbit liver during experimental myocardial infarction and from pig myocardium upon 15-min of autolysis were found to increase their activity in aminoacylation. Direct correlations between the activities of high molecular weight complexes and of the total extracts were not observed. It was shown that the specific activity of endogenous inorganic pyrophosphatase increased markedly during the ischemia of myocardium both in total myocardium extracts and in high molecular weight complexes.
Subject(s)
Amino Acyl-tRNA Synthetases/metabolism , Coronary Disease/enzymology , Liver/enzymology , Myocardium/enzymology , Animals , Autolysis/enzymology , In Vitro Techniques , Molecular Weight , Myocardial Infarction/enzymology , Pyrophosphatases/metabolism , Rabbits , SwineABSTRACT
After ligation of coronary artery an initial increase in LDH activity in liver tissue was followed by its decrease. Minimal enzymatic activity in liver tissue correlated with maximal activity in blood serum within 1-3 days. Among LDH isoenzymes the "pure" fractions were most markedly altered: LDH1 was decreased in liver tissue and increased in blood serum, LDH5 was increased in the both tissues within later periods after normalization of total activity. Enzymatic activity of LDH, LDH1 and LDH5 was shown to correlate in liver tissue and blood serum.
Subject(s)
L-Lactate Dehydrogenase/metabolism , Liver/enzymology , Myocardial Infarction/enzymology , Animals , Clinical Enzyme Tests , Coronary Vessels/physiology , Disease Models, Animal , Isoenzymes , Kinetics , L-Lactate Dehydrogenase/blood , Male , RabbitsABSTRACT
An acceptor activity of tRNA for glycine, glutamic acid, leucine, serine and phenylalanine was decreased in rabbit liver tissue within 6, 12 and 24 hrs after myocardial infarction; the activity was reduced within 72 hrs. Heating of tRNA under conditions of transition of biologically inactive conformations into active forms led to reduction of the acceptor activity. Contrary to tRNAs a pronounced activation of glycyl-, glutamyl-, leucyl- and phenylalanyl-tRNA synthetases was observed in liver extracts within 6, 12, 24 and 72 hrs after myocardial infarction. A correlation between the activation of these enzymes and alterations in their activity after association with high molecular complexes was found only for several aminoacyl-tRNA synthetases studied. The rate of tRNA aminoacylation specific for alanine, and alanyl-tRNA synthetase activity were unaltered within all the periods of myocardial infarction.
Subject(s)
Amino Acyl-tRNA Synthetases/metabolism , Liver/metabolism , Myocardial Infarction/metabolism , RNA, Transfer/metabolism , Alanine-tRNA Ligase/metabolism , Animals , Disease Models, Animal , Kinetics , RabbitsABSTRACT
The composition of high-molecular complexes of aminoacyl-tRNA-synthetases (ARSase) from the rabbit liver was studied on the first day after reproduction of the experimental myocardium infarction. The studies revealed an increase in the glutamyl-, leucyl-, lysyl- and a decrease in the glycyl- and seryl-tRNA-synthetase activities and redistribution of the last two enzymes from the composition of the complexes into a lower-molecular fraction of postribosomal supernatant fluid. Under the experimental myocardium infarction the complexes reveal a significant decrease in the content of phospholipids and variations in the electrophoretic mobility of protein fractions. An assumption is advanced that a disturbed protein biosynthesis in the liver resulted from the experimental myocardium infarction causes changes in the structural organization of the ARSase complexes.
