Effects of hypothyroidism on myosin heavy chain composition and fibre types of fast skeletal muscles in a small marsupial, antechinus flavipes

Zhong, Wendy W. H. and Withers, Kerry W. and Hoh, Joseph F. Y. (2010) Effects of hypothyroidism on myosin heavy chain composition and fibre types of fast skeletal muscles in a small marsupial, antechinus flavipes. Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology, 180 (4). pp. 531-544. ISSN 0174-1578


Effects of drug-induced hypothyroidism on myosin heavy chain (MyHC) content and fibre types of fast skeletal muscles were studied in a small marsupial, Antechinus flavipes. SDS-PAGE of MyHCs from the tibialis anterior and gastrocnemius revealed four isoforms, 2B, 2X, 2A and slow, in that order of decreasing abundance. After 5 weeks treatment with methimazole, the functionally fastest 2B MyHC significantly decreased, while 2X, 2A and slow MyHCs increased. Immunohistochemistry using monospecific antibodies to each of the four MyHCs revealed decreased 2b and 2x fibres, and increased 2a and hybrid fibres co-expressing two or three MyHCs. In the normally homogeneously fast superficial regions of these muscles, evenly distributed slow-staining fibres appeared, resembling the distribution of slow primary myotubes in fast muscles during development. Hybrid fibres containing 2A and slow MyHCs were virtually absent. These results are more detailed but broadly similar to the earlier studies on eutherians. We hypothesize that hypothyroidism essentially reverses the effects of thyroid hormone on MyHC gene expression of muscle fibres during myogenesis, which differ according to the developmental origin of the fibre: it induces slow MyHC expression in 2b fibres derived from fast primary myotubes, and shifts fast MyHC expression in fibres of secondary origin towards 2A, but not slow, MyHC.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Author version not held.
Faculty / Department / School: Historic - Faculty of Sciences - Department of Biological and Physical Sciences
Date Deposited: 10 Apr 2010 02:20
Last Modified: 22 Jul 2014 22:22
Uncontrolled Keywords: marsupial; skeletal muscle; myosin; fibre types; hypothyroidism; immunohistochemistry
Fields of Research : 06 Biological Sciences > 0601 Biochemistry and Cell Biology > 060104 Cell Metabolism
11 Medical and Health Sciences > 1101 Medical Biochemistry and Metabolomics > 110107 Metabolic Medicine
06 Biological Sciences > 0606 Physiology > 060604 Comparative Physiology
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970106 Expanding Knowledge in the Biological Sciences
Identification Number or DOI: 10.1007/s00360-009-0431-8
URI: http://eprints.usq.edu.au/id/eprint/7349

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