title: Myosin heavy chain concentration, synthesis rate and degradation rate in normal and dystrophic chicken muscle cells in culture.
abstract: Myosin heavy chain concentrations, synthesis rates and degradation rates were studied in muscle cell cultures prepared from the breast muscle of 13-day normal (white leghorn) and dystrophic (line 307) chicken embryos. Muscle cells were studied after 7 days in culture, at which time they had reached a steady state with respect to myofibrillar protein synthesis and degradation. The quantity of myosin heavy chain was 10.5 +/- 0.9 micrograms/culture (n = 32) in normal cells and 8.10 +/- 1.2 micrograms/culture (n = 31) in dystrophic cells. However, the myosin heavy chain synthesis rate was 23 500 molecules/min/nucleus in normal cells and 39 900 molecules/min/nucleus in dystrophic cells, as determined by pulse labeling with [3H]leucine and measurement of the specific radioactivity of tRNA precursor pools. Myosin heavy chain half-lives rates were calculated to be 30.6 h in normal cells and 15.6 h in dystrophic cells when corrections were made for reutilization of [3H]leucine. Thus, dystrophic muscle cultures accumulate less myosin heavy chain, despite their faster synthesis rate, because of faster degradation of myosin heavy chain.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D009132:Muscles / Q000378:metabolism*; D009137:Muscular Dystrophy, Animal / Q000378:metabolism*; D009218:Myosins / Q000096:biosynthesis / Q000378:metabolism*; D014316:Tritium
chemical_list: D014316:Tritium; D009218:Myosins; D007930:Leucine