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Seasonal differences in activities of rabbit liver tRNA and aminoacyl-tRNA synthetases specific for valine and arginine under myocardial ischemia.

UNLABELLED
The objective of this study was to examine the acceptor activities of tRNA for amino acids, valine and arginine, and the activities of the corresponding aminoacyl-tRNA synthetases of normal rabbit liver and 6, 12 and 24 h after experimental myocardial ischemia in different seasons of the year.


MATERIAL AND METHODS
Male rabbits (2.5-3.5 kg) were used. Acute myocardial ischemia was induced by occlusion of the left anterior descending coronary artery. tRNA and aminoacyl-tRNA synthetases were isolated from control rabbit liver and 6, 12 and 24 h after experimental myocardial ischemia in autumn (September and October) and winter (December and January). The acceptor activity of tRNA and the activity of valyl- and arginyl-tRNA synthetases were determined using 14C-labeled amino acids, valine and arginine.


RESULTS
The results showed that acceptor activity of rabbit liver tRNA for valine and arginine under 6, 12 and 24 h experimental myocardial ischemia in autumn was higher by 24-35% than in winter. Activities of rabbit liver valyl- and arginyl-tRNA synthetases under 6, 12 and 24 h experimental myocardial ischemia in autumn were lower by 15-32% than in winter. No differences in the activity of tRNA and aminoacyl-tRNA synthetases between control groups of both seasons were observed.


CONCLUSIONS
The experimental data suggest that acceptor activity of rabbit liver tRNA for valine and arginine and activity of valyl- and arginyl-tRNA synthetases under 6, 12 and 24 h experimental myocardial ischemia are different in autumn and winter. The decrease of acceptor activity of tRNA for valine and arginine after experimental myocardial ischemia correlates with an increase in the activity of valyl- and arginyl-tRNA synthetases both in autumn and winter. It may be part of the compensatory mechanism of the cell to keep synthesis of protein in a normal range under extreme conditions.