Protein metabolism in hypertrophied heart muscle.

Abstract

The following aspects of protein metabolism in myocardium are discussed: (1) The kinetics of labeling of aminoacyl-transfer ribonucleic acid (tRNA) and the intracellular free amino acid pool. The specific activity of leucyl-tRNA correlates closely with that of the extracellular leucine during the first 15 minutes after intravenous injection of (/sup 3/H)leucine. Equilibrium of the leucyl-tRNA with total intracellular leucine is reached at a later time. (2) Determination of the fractional rate constant (k) of myosin synthesis with leucyl-tRNA as precursor. For a period between 15 and 30 minutes after intravenous injection, the k value was approximately 0.1 day/sup -1/(t/2 approximately = 6 days). (3) Synthesis and degradation of mitochondrial components in hypertrophied heart. Cardiac cytochrome c increases faster than the remainder of cellular proteins in the first day after aortic constriction. The results of labeling with delta-aminolevulinic acid indicate increased rate of synthesis and decreased rate of degradation of cytochrome c. (4) Role of lysosomes in regression of cardiac hypertrophy. During the period of rapid fall in cardiac mass and RNA after removal of the constricting band, the activities of cathepsin D and ribonuclease were found unchanged. (5) Properties of calcium-activated neutral protease (CAF), which specifically removes Z lines frommore » myofibrils. It was shown that CAF treatment of myofibrils results in the disappearance of a single protein, ..cap alpha..-actinin.« less