title: The pathways of protein synthesis and degradation in normal heart and during development and regression of cardiac hypertrophy.
abstract: The half-life of cardiac myosin heavy chains (HC) was determined, with leucyl-tRNA as precursor, to be 5.4 days. Myosin HC are labeled more rapidly than actin; myosin light chains (LC1 and LC2) are labeled more slowly than HC. The observed differences are attributable to heterogeneity in the half-lives, e.g., actin, and to the effect of dilution by the existing macromolecular precursor pool (LC1 and LC2). Cardiac and skeletal muscle contain a population of filaments that can be released from myofibrils by ATP-relaxing solution. The easily released filaments (ERF) are devoid of alpha-actinin and M-protein. Labeling of ERF is more rapid than that of residual myofibrils. Cardiac and skeletal muscle contains calcium-activated neutral protease, which selectively removes alpha-actinin when incubated with isolated myofibrils. During development of pressure-induced cardiac hypertrophy, the labeling of LC2 is increased. In regressing cardiac hypertrophy the activities of free and total cathepsin D and of acidic RNase are unaltered.
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002250:Carbon Radioisotopes; D006332:Cardiomegaly / Q000378:metabolism* / Q000503:physiopathology; D002403:Cathepsins / Q000378:metabolism; D005260:Female; D006207:Half-Life; D007700:Kinetics; D007930:Leucine; D008247:Lysosomes / Q000201:enzymology; D009124:Muscle Proteins / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D051381:Rats; D012260:Ribonucleases / Q000378:metabolism
chemical_list: D000199:Actins; D002250:Carbon Radioisotopes; D009124:Muscle Proteins; D012343:RNA, Transfer; D012260:Ribonucleases; D002403:Cathepsins; D009218:Myosins; D007930:Leucine