Protein metabolism in chicken muscle cell cultures treated with cimaterol.
Primary muscle cell cultures were prepared from the leg muscle of 12-d broiler chicken embryos. The partitioning agent cimaterol (10(-6) to 10(-10) M) was added on d 1 and each day thereafter, and cells were studied after 7 d in culture. Cimaterol had no effect at any level either on the percentage of nuclei within multinucleated myotubes or on the total number of nuclei within myotubes. At 10(-7) M cimaterol, the quantity of the myofibrillar protein fraction was increased by 25.1 +/- 8.0% (P less than .05) and the quantity of myosin heavy chain was increased by 30.9 +/- 4.5% (P less than .05). To understand the basis for the increase in myofibrillar protein, the incorporation rate of [3H]Leu was measured in pulse labeling experiments. The apparent synthesis rate of the soluble protein fraction and the crude myofibrillar fraction was not significantly increased by cimaterol; however, cimaterol levels greater than 10(-8) M caused a 10 to 12% increase (P less than .05) in the incorporation rate of [3H]Leu into myosin heavy chain. The effect of cimaterol on release of [3H]Leu from prelabeled protein also was assessed in pulse-chase experiments; the apparent rate of protein degradation was inhibited by 10 to 15% (P less than .05) at the higher levels of cimaterol. Dot blot analysis indicated that the quantity of myosin heavy chain mRNA was elevated in cimaterol-treated cultures. Thus, the increased quantity of myofibrillar proteins in embryonic broiler muscle cell cultures is the combined result of a stimulation in the rate of protein synthesis and an inhibition in the rate of protein degradation.
Young
R B
RB
University of Alabama, Huntsville 35899.
Moriarity
D M
DM
McGee
C E
CE
Farrar
W R
WR
Richter
H E
HE
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D004983:Ethanolamines / Q000494:pharmacology*; D009124:Muscle Proteins / Q000096:biosynthesis / Q000378:metabolism*; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D009210:Myofibrils / Q000378:metabolism; D009218:Myosins / Q000096:biosynthesis / Q000378:metabolism
D000318:Adrenergic beta-Agonists; D004983:Ethanolamines; D009124:Muscle Proteins; D009218:Myosins; C047411:cimaterol