Bulletin of Equine Research Institute
Online ISSN : 1884-4626
Print ISSN : 0386-4634
ISSN-L : 0386-4634
Molecular Analysis of Horse Skeletal Muscle Myosin
Mamoru YAMAGUCHIAlissa WINNARDKazushige TAKEHANAMichio MUGURUMAShuji YAMANOLu AIPINGJerome MASTYToshiharu OBAMaureen HUNTERHiroyasu YOSHIKAWATakashi YOSHIKAWA
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1993 Volume 1993 Issue 30 Pages 15-25

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Abstract

Horse skeletal muscle myosin was isolated from nine distinct muscles; transverse pectoral, gluteus medius, extensor carpi radialis, gastrocnemius, descending pectoral, internal intercostal, longus coli, diaphragm and masseter.
The light and heavy chain subunits of myosin were focused on to determine their predisposition to associate with fast or slow twitch fibers and the impact of their specific distribution.
A 15% SDS separating gel in Tris buffer was used for light chain, and for heavy chain study 5% gels with 25% glycerol. Proteins were quantitated with a laser-beam densitometer (LKB) connected to a computer programmed integrator.
The result showed that extensor carpi radialis and gastrocnemius were typical fast twitch muscles, as evidence by the preponderance of fast-twitch fibers in heavy chains (>90% HCf) and light chains (100% LC1f+LC2f). Descending pectoral (D. P.) and internal intercostal (I. I.) can be classified as intermediate with a much greater content of fast-twitch light chains LC1f and LC2f, than of slow-twitch light chains LC1s and LC2s. The masseter can be classified as typical slow-twitch muscle on the basis of light and heavy chain composition. Longus coilli and diaphragm were also intermediate with respect to light chain composition, containing LC1s and its isoform and LC2s as well as LC1f, however, heavy chains comprised only slow-twitch fibers (100% HCs). Internal intercostal, extensor carpi radialis and diaphragm contain an isoform of LC1s. Both I. I. and D. P. contain almost equal portions of HCf, and HCs. The transverse pectoral and gluteus medius can be classified as fast-twitch muscle on the basis of the predominance of the LC1f and LC2f subunits and the appearance of detectable amounts of LC3f. Almost 100% of the 2 heavy chains in these muscles were HCf. The diversity found in chain distribution among skeletal muscle myosin from a single horse was unexpected.

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