AJP - Endocrinology and Metabolism, Vol 268, Issue 5 E858-E865, Copyright © 1995 by American Physiological Society
Bovine fast-twitch myosin light chain 1: cloning and mRNA amount in muscle of cattle treated with clenbuterol
S. B. Smith, S. K. Davis, J. J. Wilson, R. T. Stone, F. Y. Wu, D. K. Garcia, D. K. Lunt and A. M. Schiavetta
Department of Animal Science, Texas A&M University, College Station 77843, USA.
The cDNA clone encoding the fast-twitch isoform of myosin light chain 1
(MLC-1f) was isolated from bovine longissimus dorsi muscle and sequenced in
M13 and pUC8. An 0.8-kb subclone, produced by digestion of the cDNA with
EcoRI, contained the portion of the molecule common to MLC-1f and MLC-3f.
The cDNA in pUC8 contained an additional 81 bp upstream of the EcoR I
digestion site, which was unique to MLC-1f. The cDNA clone was used to
measure MLC-1f mRNA in longissimus dorsi muscle of cattle chronically
administered the beta-adrenergic agonist clenbuterol. Treatment with
clenbuterol for 50 days increased succinic dehydrogenase negative (type
IIB) and positive (types I and IIA) myofiber cross-sectional areas by 25%.
After the 50-day treatment period, the amount of MLC-1f mRNA was 90%
greater in longissimus dorsi muscle of treated animals than in the initial
group. This effect was lost when clenbuterol treatment was withdrawn for a
78-day period, during which time muscle growth in the treated animals
stopped completely. We conclude that we have cloned the bovine cDNA for
MLC-1f, which has provided additional evidence that beta-adrenergic
agonists increase myofibrillar gene expression.
