title: Synthesis rates of protein in the Langendorff-perfused rat heart in the presence and absence of insulin, and in the working heart.
abstract: The synthesis rates of total heart protein and of sarcoplasmic and myofibrillar protein fractions have been determined by perfusion of isolated rat hearts with [(14)C]tyrosine at constant specific radioactivity. In hearts perfused without insulin, both myofibrillar and sarcoplasmic proteins were synthesized at a fractional rate of 10-11% per day. This corresponds to a half-life for synthesis of about 7 days. The effect of added insulin was to increase the rate of heart-protein synthesis to a half-life of 3-4 days. With hearts perfused via the left atrium and performing external work, there was a rise in the specific radioactivity of intracellular free tyrosine, and the half-life for synthesis of proteins was 3-4 days. The extent of labelling of individual myofibrillar proteins was estimated after polyacrylamide-gel electrophoresis of solubilized myofibrils in the presence of sodium dodecyl sulphate. No particular protein showed an unusually high or low specific radioactivity after labelling in perfusion. Insulin caused a general increase in labelling of all the proteins analysed.
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D004591:Electrophoresis, Polyacrylamide Gel; D006207:Half-Life; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D008433:Mathematics; D009124:Muscle Proteins / Q000096:biosynthesis*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism; D010477:Perfusion; D051381:Rats; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D007328:Insulin; D009124:Muscle Proteins; D014443:Tyrosine