The slow tonic anterior latissimus dorsi (ALD) muscle of the chicken contains two isomyosins, namely SM-1 and SM-2. The proportions of the two isoforms change with age, SM-2 expression increasing at the expense of SM-1. Applying a load on the wing increases the rate and extent of SM-1 replacement. Here we have demonstrated that decreasing the load by removal of the distal portion of the wing in 1-week-old chickens had an effect opposite to that of overloading in that it slowed muscle growth and the rate of SM-1 elimination. Experimental unloading of muscles previously weighted for 1 or 3 weeks slowed the growth rate of muscles, with consequent regression of relative hypertrophy; however, it did not lead to the reexpression of SM-1 myosin. This indicates that the overload-induced changes in myosin expression are not readily reversible. Nerve section produced unexpected results, in that it advanced the normal developmental shift in myosin expression toward predominance of the SM-2 isoform, similar to the effect of muscle overload.
Research Article|June 01 1989
Regulation of expression of avian slow myosin heavy-chain isoforms
S K Reid;
J M Kennedy;
1*Department of Medicine, University of Chicago, Chicago, IL 60637, U.S.A.
†Department of Anatomy, University of Chicago, Chicago, IL 60637, U.S.A.
‡§Department of Anatomy and Developmental Biology, University College (and Middlesex School of Medicine), London WCIE 6BT, U.K.
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Biochem J (1989) 260 (2): 449-454.
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S K Reid, J M Kennedy, N Shimizu, A Stewart, G Vrbova, R Zak; Regulation of expression of avian slow myosin heavy-chain isoforms. Biochem J 1 June 1989; 260 (2): 449–454. doi: https://doi.org/10.1042/bj2600449
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